Materials Science › Materials Chemistry

Silicon Nanostructures and Photoluminescence

Works Count: 44465

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This cluster of papers focuses on the synthesis, properties, and applications of porous silicon nanoparticles and nanostructures. It covers topics such as drug delivery, bioimaging, optical properties, luminescence, and biocompatibility of porous silicon. The research also explores the use of silicon quantum dots and electroluminescence in various biomedical and optoelectronic applications.

Keywords

Porous Silicon; Nanoparticles; Luminescent; Drug Delivery; Optical Properties; Bioimaging; Photoluminescence; Silicon Quantum Dots; Biocompatible; Electroluminescence

Optical gain in silicon nanocrystals

2000-11-01

Lorenzo Pavesi , Luca Dal Negro , Cláudio Mazzoleni +2 more

Metal-assisted chemical etching in HF/H2O2 produces porous silicon

2000-10-16

X. Li , Paul W. Bohn

A simple and effective method is presented for producing light-emitting porous silicon (PSi). A thin (d&lt;10 nm) layer of Au, Pt, or Au/Pd is deposited on the (100) Si surface … A simple and effective method is presented for producing light-emitting porous silicon (PSi). A thin (d&lt;10 nm) layer of Au, Pt, or Au/Pd is deposited on the (100) Si surface prior to immersion in a solution of HF and H2O2. Depending on the type of metal deposited and Si doping type and doping level, PSi with different morphologies and light-emitting properties is produced. PSi production occurs on the time scale of seconds, without electrical current, in the dark, on both p- and n-type Si. Thin metal coatings facilitate the etching in HF and H2O2, and of the metals investigated, Pt yields the fastest etch rates and produces PSi with the most intense luminescence. A reaction scheme involving local coupling of redox reactions with the metal is proposed to explain the metal-assisted etching process. The observation that some metal remains on the PSi surface after etching raises the possibility of fabricating in situ PSi contacts.

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Quantum confinement and light emission in SiO2/Si superlattices

1995-11-01

Z. H. Lu , D. J. Lockwood , J.‐M. Baribeau

19.8% efficient “honeycomb” textured multicrystalline and 24.4% monocrystalline silicon solar cells

1998-10-05

Jianhua Zhao , Aihua Wang , Martin A. Green +1 more

Multicrystalline silicon wafers, widely used in commercial photovoltaic cell production, traditionally give much poorer cell performance than monocrystalline wafers (the previously highest performance laboratory devices have solar energy conversion efficiencies … Multicrystalline silicon wafers, widely used in commercial photovoltaic cell production, traditionally give much poorer cell performance than monocrystalline wafers (the previously highest performance laboratory devices have solar energy conversion efficiencies of 18.6% and 24.0%, respectively). A substantially improved efficiency for a multicrystalline silicon solar cell of 19.8% is reported together with an incremental improvement in monocrystalline cell efficiency to 24.4%. The improved multicrystalline cell performance results from enshrouding cell surfaces in thermally grown oxide to reduce their detrimental electronic activity and from isotropic etching to form an hexagonally symmetric “honeycomb” surface texture. This texture reduces reflection loss as well as substantially increasing the cell’s effective optical thickness by causing light to be trapped within the cell by total internal reflection.

Electropolishing Silicon in Hydrofluoric Acid Solutions

1958-01-01

Dennis R. Turner

Silicon is electropolished in hydrofluoric acid solutions if a critical current density is exceeded. Below the critical c.d., silicon dissolution is largely divalent, and a thick solid layer forms. This … Silicon is electropolished in hydrofluoric acid solutions if a critical current density is exceeded. Below the critical c.d., silicon dissolution is largely divalent, and a thick solid layer forms. This film is unstable and reacts slowly with the electrolyte to form tetravalent silicon and hydrogen gas. In the electro‐polishing region, silicon dissolution is mainly tetravalent with the formation of a very thin high resistance type of film.

Size-controlled highly luminescent silicon nanocrystals: A SiO/SiO2 superlattice approach

2002-01-28

Margit Zacharias , J. Heitmann , R. Scholz +3 more

Phase separation and thermal crystallization of SiO/SiO2 superlattices results in ordered arranged silicon nanocrystals. The preparation method which is fully compatible with Si technologies enables independent control of particle size … Phase separation and thermal crystallization of SiO/SiO2 superlattices results in ordered arranged silicon nanocrystals. The preparation method which is fully compatible with Si technologies enables independent control of particle size as well as of particle density and spatial position by using a constant stoichiometry of the layers. Transmission electron microscopy investigations confirm the size control in samples with an upper limit of the nanocrystal sizes of 3.8, 2.5, and 2.0 nm without decreasing the silicon nanocrystal density for smaller sizes. The nanocrystals show a strong luminescence intensity in the visible and near-infrared region. A size-dependent blueshift of the luminescence and a luminescence intensity comparable to porous Si are observed. Nearly size independent luminescence intensity without bleaching effects gives an indirect proof of the accomplishment of the independent control of crystal size and number.

Green’s-function approach to linear response in solids

1987-05-04

Stefano Baroni , Paolo Giannozzi , Andrea Testa

We present a new scheme to study the linear response of crystals which combines the advantages of the dielectric-matrix and supercell (``direct'') approaches yet avoids many of their drawbacks. The … We present a new scheme to study the linear response of crystals which combines the advantages of the dielectric-matrix and supercell (``direct'') approaches yet avoids many of their drawbacks. The numerical complexity of the algorithm is of the same order as that of a self-consistent calculation for the unperturbed system. The method is not restricted to local perturbations as the dielectric-matrix one nor to short wavelengths as the direct one. As an application, we calculate the long-wavelength optical phonons in Si and GaAs, both transverse and longitudinal, using norm-conserving pseudopotentials, and without any use of supercells.

Visible light emission due to quantum size effects in highly porous crystalline silicon

1991-09-01

A.G. Cullis , Leigh Canham

The structural and luminescence properties of porous silicon

1997-08-01

A. G. Cullis , Leigh Canham , P. D. J. Calcott

A large amount of work world-wide has been directed towards obtaining an understanding of the fundamental characteristics of porous Si. Much progress has been made following the demonstration in 1990 … A large amount of work world-wide has been directed towards obtaining an understanding of the fundamental characteristics of porous Si. Much progress has been made following the demonstration in 1990 that highly porous material could emit very efficient visible photoluminescence at room temperature. Since that time, all features of the structural, optical and electronic properties of the material have been subjected to in-depth scrutiny. It is the purpose of the present review to survey the work which has been carried out and to detail the level of understanding which has been attained. The key importance of crystalline Si nanostructures in determining the behaviour of porous Si is highlighted. The fabrication of solid-state electroluminescent devices is a prominent goal of many studies and the impressive progress in this area is described.

Visible electroluminescence from porous silicon

1992-01-20

Nobuyoshi Koshida , Hideki Koyama

It is demonstrated that photoluminescent porous Si (PS) layers exhibit definitely visible electroluminescence (EL). The PS layers were formed by anodization of single-crystal nondegenerate p-type Si wafers in an HF … It is demonstrated that photoluminescent porous Si (PS) layers exhibit definitely visible electroluminescence (EL). The PS layers were formed by anodization of single-crystal nondegenerate p-type Si wafers in an HF solution. The experimental EL cells are of the form semitransparent metal/PS layer/p-type Si/Al electrode. These cells show a rectifying junction behavior. When the forward current density reaches a certain value, stable visible (orange) light is uniformly emitted through a semitransparent electrode. A possible explanation of this is the radiative transition due to electron and hole injection into quantized states in PS.

Desorption–ionization mass spectrometry on porous silicon

1999-05-01

Jing Wei , Jillian M. Buriak , Gary Siuzdak

Porous silicon in drug delivery devices and materials☆

2008-04-11

Emily J. Anglin , Lingyun Cheng , William R. Freeman +1 more

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Theory of the quantum confinement effect on excitons in quantum dots of indirect-gap materials

1992-12-15

T. Takagahara , Kyozaburo Takeda

The quantum confinement effect on excitons in quantum dots of indirect-gap materials is investigated and a mechanism that induces an indirect-to-direct conversion of the character of the optical transition is … The quantum confinement effect on excitons in quantum dots of indirect-gap materials is investigated and a mechanism that induces an indirect-to-direct conversion of the character of the optical transition is clarified. The exciton transition energy and the exciton binding energy are calculated and found to be in good agreement with experimental results on Si and Ge nanostructures. The large exciton binding energy in Si and Ge quantum dots suggests that the photoluminescence from these nanostructures is of excitonic origin even at room temperature. The estimated radiative lifetime of excitons is strongly size dependent and varies from nanosecond to millisecond corresponding to the diameter from \ensuremath{\sim}10 to \ensuremath{\sim}30 \AA{}. These theoretical results suggest strongly the importance of the quantum confinement effect in the luminescence processes of porous Si.

An all-silicon Raman laser

2005-01-01

Haisheng Rong , Ansheng Liu , Richard Jones +5 more

Organometallic Chemistry on Silicon and Germanium Surfaces

2002-03-08

Jillian M. Buriak

ADVERTISEMENT RETURN TO ISSUEArticleNEXTOrganometallic Chemistry on Silicon and Germanium SurfacesJillian M. BuriakView Author Information Department of Chemistry, 1393 Brown Laboratories, Purdue University, West Lafayette, Indiana 47907-1393 Cite this: Chem. Rev. … ADVERTISEMENT RETURN TO ISSUEArticleNEXTOrganometallic Chemistry on Silicon and Germanium SurfacesJillian M. BuriakView Author Information Department of Chemistry, 1393 Brown Laboratories, Purdue University, West Lafayette, Indiana 47907-1393 Cite this: Chem. Rev. 2002, 102, 5, 1271–1308Publication Date (Web):March 8, 2002Publication History Received10 July 2001Published online8 March 2002Published inissue 1 May 2002https://pubs.acs.org/doi/10.1021/cr000064shttps://doi.org/10.1021/cr000064sresearch-articleACS PublicationsCopyright © 2002 American Chemical SocietyRequest reuse permissionsArticle Views11386Altmetric-Citations1570LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose SUBJECTS:Hydrocarbons,Hydrosilylation,Monolayers,Porous materials,Silicon Get e-Alerts

Silicon nanostructures for third generation photovoltaic solar cells

2006-01-23

Gavin Conibeer , Martin A. Green , Richard Corkish +7 more

Porous silicon: a quantum sponge structure for silicon based optoelectronics

2000-04-01

O. Bisi , Stefano Ossicini , Lorenzo Pavesi

High-Yield Plasma Synthesis of Luminescent Silicon Nanocrystals

2005-03-05

Lorenzo Mangolini , Elijah Thimsen , Uwe Kortshagen

Light emission from silicon based on quantum confinement in nanoscale structures has sparked intense research into this field ever since its discovery about 15 years ago. A barrier to the … Light emission from silicon based on quantum confinement in nanoscale structures has sparked intense research into this field ever since its discovery about 15 years ago. A barrier to the widespread utilization of luminescent silicon nanocrystals in such diverse application areas as optoelectronics, solid-state lighting for general illumination, or fluorescent agents for biological applications has been the lack of a simple, high-yield synthesis approach. Here we report a scaleable single-step synthesis process for luminescent silicon nanocrystals based on a low-pressure nonthermal plasma.

Quantum size effects on photoluminescence in ultrafine Si particles

1990-06-11

H. Takagi , H. Ogawa , Yuzo Yamazaki +2 more

Visible photoluminescence was observed in ultrafine Si particles at room temperature. Transmission electron microscopy revealed that Si microcrystallites were embedded in a Si oxide matrix for the sample which emitted … Visible photoluminescence was observed in ultrafine Si particles at room temperature. Transmission electron microscopy revealed that Si microcrystallites were embedded in a Si oxide matrix for the sample which emitted the light. The emission energy depended on crystallite size in the range from 2.8 to 5 nm. The inverse relation between emission energy and the square of the crystallite size indicates that carrier confinement in the Si microcrystallites causes this photoluminescence phenomenon.

Low-dimensional systems: quantum size effects and electronic properties of semiconductor microcrystallites (zero-dimensional systems) and some quasi-two-dimensional systems

1993-04-01

A. D. Yoffe

Abstract This review is concerned with quantum confinement effects in low-dimensional semiconductor systems. The emphasis is on the optical properties, including luminescence, of nanometre-sized microcrystallites, also referred to as zerodimensional … Abstract This review is concerned with quantum confinement effects in low-dimensional semiconductor systems. The emphasis is on the optical properties, including luminescence, of nanometre-sized microcrystallites, also referred to as zerodimensional systems. There is some discussion on certain of the two-dimensional systems, such as thin films and layer structures. The increase in energy of excitation peaks (blue shift) as the radius R of a microcrystallite is reduced is treated theoretically, and experimental data when they are available are used to assess the reliability of the different models that have been used. These experiments normally make use of microcrystallites dispersed in a large-bandgap matrix such as glass, rocksalt, polymers, zeolites or liquids. Exciton binding energies E b are larger than for bulk semiconductors, and oscillator strengths are higher for the microcrystallites. The regimes of direct interest are as follows. Firstly there is the so-called weak-confinement regime where R is greater than the bulk exciton Bohr radius a B. Experimentally, semiconductors such as CuCl with a B ≈ 7 Å, are suitable for study in this case. Secondly there is the moderate-confinement regime, where R ≈ a B, and a h < R < a h, a h and a e being the hole and electron Bohr radii respectively. Finally there is the strong-confinement regime, with R < a B, and R < a h, a e. For this case we are concerned with a ladder of discrete energy levels, as in molecular systems, rather than energy bands. The electrons and holes are treated as independent particles, and for excited states we refer to electron-hole pairs rather than excitons. Suitable materials for investigation in this regime are the II–VI semiconductors, and also GaAs and Ge, for which a B is relatively large. Although a number of different theoretical models have been used, none can be described as completely first-principles calculations, and there is room for improvement on this aspect. However, useful expressions have been developed by Brus and by Lippens and Lannoo, giving the energy of excited states as a function of R, in terms of the bulk energy gap, kinetic energy, Coulomb energy and correlation energy. Other phenomena discussed are firstly biexciton formation by the use of high intensity laser beams and secondly nonlinear optical effects. Strong nonlinearities and short decay times for excited states have been predicted, and the models developed cover both the resonant and the non-resonant cases. The possibility of using microcrystallites embedded at reasonable concentrations in a glass matrix in the field of optical communications and optical switching is also considered.

Calibration of the Raman spectrum to the oxygen stoichiometry of nanophase TiO2

1990-08-27

John C. Parker , Richard W. Siegel

Calibration curves of the Raman spectrum of nanophase TiO2 to the material’s oxygen stoichiometry are presented. The thermogravimetric analysis studies used to determine the oxygen-titanium ratio are also discussed. Calibration curves of the Raman spectrum of nanophase TiO2 to the material’s oxygen stoichiometry are presented. The thermogravimetric analysis studies used to determine the oxygen-titanium ratio are also discussed.

Quantum Confinement in Size-Selected, Surface-Oxidized Silicon Nanocrystals

1993-11-19

William L. Wilson , Paul F. Szajowski , Louis E. Brus

The dynamics and spectroscopy of silicon nanocrystals that emit at visible wavelengths were analyzed. Size-selective precipitation and size-exclusion chromatography cleanly separate the silicon nanocrystals from larger crystallites and aggregates and … The dynamics and spectroscopy of silicon nanocrystals that emit at visible wavelengths were analyzed. Size-selective precipitation and size-exclusion chromatography cleanly separate the silicon nanocrystals from larger crystallites and aggregates and provide direct evidence for quantum confinement in luminescence. Measured quantum yields are as high as 50 percent at low temperature, principally as a result of efficient oxide passivation. Despite a 0.9-electron-volt shift of the band gap to higher energy, the nanocrystals behave fundamentally as indirect gap materials with low oscillator strength.

Fine Structure in the Absorption-Edge Spectrum of Si

1958-09-01

G. G. Macfarlane , Thomas McLean , J E Quarrington +1 more

Measurements of the absorption spectrum of Si, made with high resolution, near the main absorption edge, at various temperatures between 4.2\ifmmode^\circ\else\textdegree\fi{}K and 415\ifmmode^\circ\else\textdegree\fi{}K, have revealed fine structure in the absorption … Measurements of the absorption spectrum of Si, made with high resolution, near the main absorption edge, at various temperatures between 4.2\ifmmode^\circ\else\textdegree\fi{}K and 415\ifmmode^\circ\else\textdegree\fi{}K, have revealed fine structure in the absorption on the long-wavelength side of this edge. This structure has been analyzed and can be interpreted in terms of indirect transitions involving, in general, phonons with energies corresponding to temperatures of 212\ifmmode^\circ\else\textdegree\fi{}K, 670\ifmmode^\circ\else\textdegree\fi{}K, 1050\ifmmode^\circ\else\textdegree\fi{}K, and 1420\ifmmode^\circ\else\textdegree\fi{}K. The form of the absorption associated with each type of phonon indicates that, as well as the formation of free electron-hole pairs taking place, excitons with a binding energy \ensuremath{\sim}0.01 ev are produced in the absorption process. The temperature dependence of the indirect energy band gap has been found and using this along with data on the intrinsic carrier density indicates an increase with temperature of the combined density-of-states effective mass of the electrons and holes. A smoothing out of the basic features of the curves is observed and shown to be consistent with relaxation broadening. A discussion of the significance of the energies of the phonons taking part in the indirect transitions to the lattice vibrational spectrum of Si is given.

Visible photoluminescence of Ge microcrystals embedded in SiO2 glassy matrices

1991-12-09

Yoshihito Maeda , Nobuo Tsukamoto , Y. Yazawa +2 more

Ge microcrystals embedded in SiO2 glassy matrices were formed by a radio-frequency magnetron cosputtering technique and then annealed at 800 °C for 30 min. The average radius of the Ge … Ge microcrystals embedded in SiO2 glassy matrices were formed by a radio-frequency magnetron cosputtering technique and then annealed at 800 °C for 30 min. The average radius of the Ge microcrystals in SiO2 was determined to be about 3 nm by means of Raman spectroscopy and high resolution electron microscope. The annealed sample showed a strong room temperature luminescence with a peak at 2.18 eV. This is consistent with quantum confinement of electrons and holes.

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A Physically Transient Form of Silicon Electronics

2012-09-28

Suk‐Won Hwang , Hu Tao , Dae‐Hyeong Kim +7 more

Reversible Implants Silicon electronics are generally designed to be stable and robust—it would be counterproductive if the key parts of your computer or cell phone slowly dissolved away while you … Reversible Implants Silicon electronics are generally designed to be stable and robust—it would be counterproductive if the key parts of your computer or cell phone slowly dissolved away while you were using it. In order to develop transient electronics for use as medical implants, Hwang et al. (p. 1640 , see the cover) produced a complete set of tools and materials that would be needed to make standard devices. Devices were designed to have a specific lifetime, after which the component materials, such as porous silicon and silk, would be resorbed by the body.

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Near-band-gap photoluminescence of Si-Ge alloys

1989-09-15

J. Weber , M. I. Alonso

The low-temperature near-band-gap photoluminescence of ${\mathrm{Si}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Ge}}_{\mathrm{x}}$ is studied over the whole composition range 0\ensuremath{\le}x\ensuremath{\le}1. We identify free- and bound-exciton processes and determine the properties of momentum-conserving phonons. From our results … The low-temperature near-band-gap photoluminescence of ${\mathrm{Si}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Ge}}_{\mathrm{x}}$ is studied over the whole composition range 0\ensuremath{\le}x\ensuremath{\le}1. We identify free- and bound-exciton processes and determine the properties of momentum-conserving phonons. From our results we determine the low-temperature band gap of the alloys. Analytical expressions are derived for the X and L bands: ${E}_{\mathrm{gx}}^{X}$(x) =1.155-0.43x+0.206${x}^{2}$ eV; ${E}_{\mathrm{gx}}^{L}$(x)=2.010-1.270x eV. The intensity and the linewidth of the various excitonic transitions are found to depend only on the statistical alloy fluctuations. No preferential clustering of Si and Ge atoms is detected.

Erbium implanted thin film photonic materials

1997-07-01

Albert Polman

Erbium doped materials are of great interest in thin film integrated optoelectronic technology, due to their Er3+intra-4f emission at 1.54 μm, a standard telecommunication wavelength. Er-doped dielectric thin films can … Erbium doped materials are of great interest in thin film integrated optoelectronic technology, due to their Er3+intra-4f emission at 1.54 μm, a standard telecommunication wavelength. Er-doped dielectric thin films can be used to fabricate planar optical amplifiers or lasers that can be integrated with other devices on the same chip. Semiconductors, such as silicon, can also be doped with erbium. In this case the Er may be excited through optically or electrically generated charge carriers. Er-doped Si light-emitting diodes may find applications in Si-based optoelectronic circuits. In this article, the synthesis, characterization, and application of several different Er-doped thin film photonic materials is described. It focuses on oxide glasses (pure SiO2, phosphosilicate, borosilicate, and soda-lime glasses), ceramic thin films (Al2O3,Y2O3, LiNbO3), and amorphous and crystalline silicon, all doped with Er by ion implantation. MeV ion implantation is a technique that is ideally suited to dope these materials with Er as the ion range corresponds to the typical micron dimensions of these optical materials. The role of implantation defects, the effect of annealing, concentration dependent effects, and optical activation are discussed and compared for the various materials.

The effects of microcrystal size and shape on the one phonon Raman spectra of crystalline semiconductors

1986-06-01

I. H. Campbell , P. M. Fauchet

Porous silicon formation mechanisms

1992-04-15

R. L. Smith , Scott D. Collins

Recent reports describing photoluminescence in porous silicon have heightened the level of interest in it as a unique electronic material, and have created a need for a more complete understanding … Recent reports describing photoluminescence in porous silicon have heightened the level of interest in it as a unique electronic material, and have created a need for a more complete understanding of the mechanism of porous silicon formation. The various models describing porous silicon formation are reviewed and the known electrochemical and morphological properties are discussed with the intention of unifying the different models into a comprehensive explanation for the formation of a porous structure in silicon. Because the specific surface dissolution chemistry is critical for a complete understanding of pore formation, some of the more prominent dissolution reactions are also reviewed and their relative importance to pore generation and morphology is discussed. Some aspects of the recently reported quantum effects are also reviewed. Because the mechanism of porous silicon formation involves a wide range of interdisciplinary fields, a considerable number of analogies and examples to related phenomena are also presented throughout the review to aid comprehension.

Electrochemistry and Electrogenerated Chemiluminescence from Silicon Nanocrystal Quantum Dots

2002-05-17

Zhifeng Ding , Bernadette M. Quinn , Santosh K. Haram +3 more

Reversible electrochemical injection of discrete numbers of electrons into sterically stabilized silicon nanocrystals (NCs) (approximately 2 to 4 nanometers in diameter) was observed by differential pulse voltammetry (DPV) in N,N'-dimethylformamide … Reversible electrochemical injection of discrete numbers of electrons into sterically stabilized silicon nanocrystals (NCs) (approximately 2 to 4 nanometers in diameter) was observed by differential pulse voltammetry (DPV) in N,N'-dimethylformamide and acetonitrile. The electrochemical gap between the onset of electron injection and hole injection-related to the highest occupied and lowest unoccupied molecular orbitals-grew with decreasing nanocrystal size, and the DPV peak potentials above the onset for electron injection roughly correspond to expected Coulomb blockade or quantized double-layer charging energies. Electron transfer reactions between positively and negatively charged nanocrystals (or between charged nanocrystals and molecular redox-active coreactants) occurred that led to electron and hole annihilation, producing visible light. The electrogenerated chemiluminescence spectra exhibited a peak maximum at 640 nanometers, a significant red shift from the photoluminescence maximum (420 nanometers) of the same silicon NC solution. These results demonstrate that the chemical stability of silicon NCs could enable their use as redox-active macromolecular species with the combined optical and charging properties of semiconductor quantum dots.

Porous silicon formation: A quantum wire effect

1991-02-25

V. Lehmann , U. Gösele

Porous silicon layers grown on nondegenerated p-type silicon electrodes in hydrofluoric acid electrolytes are translucent for visible light, which is equivalent to an increased band gap compared to bulk silicon. … Porous silicon layers grown on nondegenerated p-type silicon electrodes in hydrofluoric acid electrolytes are translucent for visible light, which is equivalent to an increased band gap compared to bulk silicon. It will be shown that a two-dimensional quantum confinement (quantum wire) in the very narrow walls between the pores not only explains the change in band-gap energy but may also be the key to better understanding the dissolution mechanism that leads to porous silicon formation.

Silicon quantum wire array fabrication by electrochemical and chemical dissolution of wafers

1990-09-03

Leigh Canham

Indirect evidence is presented that free-standing Si quantum wires can be fabricated without the use of epitaxial deposition or lithography. The novel approach uses electrochemical and chemical dissolution steps to … Indirect evidence is presented that free-standing Si quantum wires can be fabricated without the use of epitaxial deposition or lithography. The novel approach uses electrochemical and chemical dissolution steps to define networks of isolated wires out of bulk wafers. Mesoporous Si layers of high porosity exhibit visible (red) photoluminescence at room temperature, observable with the naked eye under &lt;1 mW unfocused (&lt;0.1 W cm−2) green or blue laser line excitation. This is attributed to dramatic two-dimensional quantum size effects which can produce emission far above the band gap of bulk crystalline Si.

An efficient room-temperature silicon-based light-emitting diode

2001-03-08

Wai Lek Ng , M. A. Lourenço , R. Gwilliam +3 more

Metal-assisted chemical etching of silicon in HF–H2O2

2008-04-13

Camille Chartier , Stéphane Bastide , Claude Lévy‐Clément

Shape Transition of Germanium Nanocrystals on a Silicon (001) Surface from Pyramids to Domes

1998-01-16

G. Medeiros‐Ribeiro , Alexander M. Bratkovski , T. I. Kamins +2 more

Chemical vapor deposition of germanium onto the silicon (001) surface at atmospheric pressure and 600 degrees Celsius has previously been shown to produce distinct families of smaller (up to 6 … Chemical vapor deposition of germanium onto the silicon (001) surface at atmospheric pressure and 600 degrees Celsius has previously been shown to produce distinct families of smaller (up to 6 nanometers high) and larger (all approximately 15 nanometers high) nanocrystals. Under ultrahigh-vacuum conditions, physical vapor deposition at approximately the same substrate temperature and growth rate produced a similar bimodal size distribution. In situ scanning tunneling microscopy revealed that the smaller square-based pyramids transform abruptly during growth to significantly larger multifaceted domes, and that few structures with intermediate size and shape remain. Both nanocrystal shapes have size-dependent energy minima that result from the interplay between strain relaxation at the facets and stress concentration at the edges. A thermodynamic model similar to a phase transition accounts for this abrupt morphology change.

Silicon-based visible light-emitting devices integrated into microelectronic circuits

1996-11-01

Karl D. Hirschman , L. Tsybeskov , S. P. Duttagupta +1 more

Recent developments in rare-earth doped materials for optoelectronics

2002-01-01

Anthony J. Kenyon

Theoretical aspects of the luminescence of porous silicon

1993-10-15

Christophe Delerue , G. Allan , M. Lannoo

The luminescence in the visible range of porous silicon is analyzed in the hypothesis of quantum confinement. We calculate the electronic and optical properties of silicon crystallites and wires with … The luminescence in the visible range of porous silicon is analyzed in the hypothesis of quantum confinement. We calculate the electronic and optical properties of silicon crystallites and wires with sizes between 0 and 4.5 nm. The band-gap energies of such confined systems are in agreement with the photon energies observed in luminescence. We calculate the radiative recombination times of the confined excitons. We conclude that experimental nonradiative processes in porous silicon are more efficient than calculated radiative ones at T=300 K. The high photoluminescence efficiency of porous silicon is due to the small probability of finding a nonradiative recombination center in silicon nanocrystallites. Recently, it has been proposed that the low-temperature dependence of the experimental radiative decay time of the luminescence of porous silicon could be explained by the exchange splitting in the fundamental exciton. We show that the influence of the valley-orbit splitting cannot be excluded. The sharp optical-absorption edge above 3.0 eV is not proof of the molecular origin of the properties of porous silicon because silicon nanostructures present a similar absorption spectrum. We calculate the nonradiative capture of electrons or holes on silicon dangling bonds and show that it is very dependent on the confinement. We find that the presence of one dangling bond at the surface of a crystallite in porous silicon must destroy its luminescent properties above 1.1 eV but can produce a luminescence below 1.1 eV due to a radiative capture on the dangling bond.

The origin of visible luminescencefrom “porous silicon”: A new interpretation

1992-01-01

Martin S. Brandt , H. D. Fuchs , M. Stutzmann +2 more

Multiple Exciton Generation in Colloidal Silicon Nanocrystals

2007-07-24

Matthew C. Beard , Kelly P. Knutsen , Pingrong Yu +5 more

Multiple exciton generation (MEG) is a process whereby multiple electron−hole pairs, or excitons, are produced upon absorption of a single photon in semiconductor nanocrystals (NCs) and represents a promising route … Multiple exciton generation (MEG) is a process whereby multiple electron−hole pairs, or excitons, are produced upon absorption of a single photon in semiconductor nanocrystals (NCs) and represents a promising route to increased solar conversion efficiencies in single-junction photovoltaic cells. We report for the first time MEG yields in colloidal Si NCs using ultrafast transient absorption spectroscopy. We find the threshold photon energy for MEG in 9.5 nm diameter Si NCs (effective band gap ≡ Eg = 1.20 eV) to be 2.4 ± 0.1Eg and find an exciton-production quantum yield of 2.6 ± 0.2 excitons per absorbed photon at 3.4Eg. While MEG has been previously reported in direct-gap semiconductor NCs of PbSe, PbS, PbTe, CdSe, and InAs, this represents the first report of MEG within indirect-gap semiconductor NCs. Furthermore, MEG is found in relatively large Si NCs (diameter equal to about twice the Bohr radius) such that the confinement energy is not large enough to produce a large blue-shift of the band gap (only 80 meV), but the Coulomb interaction is sufficiently enhanced to produce efficient MEG. Our findings are of particular importance because Si dominates the photovoltaic solar cell industry, presents no problems regarding abundance and accessibility within the Earth's crust, and poses no significant environmental problems regarding toxicity.

Formation and application of porous silicon

2002-10-07

H. Föll , M. Christophersen , Jürgen Carstensen +1 more

Biodegradable luminescent porous silicon nanoparticles for in vivo applications

2009-02-22

Ji‐Ho Park , Luo Gu , Geoffrey von Maltzahn +3 more

Electrooptical effects in silicon

1987-01-01

Richard Soref , B. R. Bennett

A numerical Kramers-Kronig analysis is used to predict the refractive-index perturbations produced in crystalline silicon by applied electric fields or by charge carriers. Results are obtained over the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" … A numerical Kramers-Kronig analysis is used to predict the refractive-index perturbations produced in crystalline silicon by applied electric fields or by charge carriers. Results are obtained over the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1.0-2.0 \mu</tex> m optical wavelength range. The analysis makes use of experimental electroabsorption spectra and impurity-doping spectra taken from the literature. For electrorefraction at the indirect gap, we find <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\Delta n = 1.3 \times 10^{5}</tex> at <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\lambda = 1.07 \mu</tex> m when <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E = 10^{5}</tex> V/cm, while the Kerr effect gives <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\Delta n = 10^{-6}</tex> at that field strength. The charge-carrier effects are larger, and a depletion or injection of 10 18 carriers/cm 3 produces an index change of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\pm1.5 \times 10^{-3}</tex> at <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\lambda = 1.3 \mu</tex> m.

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Nanodome Solar Cells with Efficient Light Management and Self-Cleaning

2009-11-05

Jia Zhu , Ching-Mei Hsu , Zongfu Yu +2 more

Here for the first time, we demonstrate novel nanodome solar cells, which have periodic nanoscale modulation for all layers from the bottom substrate, through the active absorber to the top … Here for the first time, we demonstrate novel nanodome solar cells, which have periodic nanoscale modulation for all layers from the bottom substrate, through the active absorber to the top transparent contact. These devices combine many nanophotonic effects to both efficiently reduce reflection and enhance absorption over a broad spectral range. Nanodome solar cells with only a 280 nm thick hydrogenated amorphous silicon (a-Si:H) layer can absorb 94% of the light with wavelengths of 400-800 nm, significantly higher than the 65% absorption of flat film devices. Because of the nearly complete absorption, a very large short-circuit current of 17.5 mA/cm(2) is achieved in our nanodome devices. Excitingly, the light management effects remain efficient over a wide range of incident angles, favorable for real environments with significant diffuse sunlight. We demonstrate nanodome devices with a power efficiency of 5.9%, which is 25% higher than the flat film control. The nanodome structure is not in principle limited to any specific material system and its fabrication is compatible with most solar manufacturing; hence it opens up exciting opportunities for a variety of photovoltaic devices to further improve performance, reduce materials usage, and relieve elemental abundance limitations. Lastly, our nanodome devices when modified with hydrophobic molecules present a nearly superhydrophobic surface and thus enable self-cleaning solar cells.

Electronic States and Luminescence in Porous Silicon Quantum Dots: The Role of Oxygen

1999-01-04

Michal V. Wolkin , Jacob Jorné , Philippe M. Fauchet +2 more

Depending on the size, the photoluminescence (PL) of silicon quantum dots present in porous silicon can be tuned from the near infrared to the ultraviolet when the surface is passivated … Depending on the size, the photoluminescence (PL) of silicon quantum dots present in porous silicon can be tuned from the near infrared to the ultraviolet when the surface is passivated with Si-H bonds. After exposure to oxygen, the PL shifts to the red by as much as 1 eV. This shift and the changes in PL intensity and decay time, show that both quantum confinement and surface passivation determine the electronic states of silicon quantum dots. A theoretical model in which new electronic states appear in the band gap of the smaller quantum dots when a $\mathrm{Si}=\mathrm{O}$ bond is formed, is in good agreement with experiments. This result clarifies the controversy regarding the PL mechanisms in porous silicon.

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Physics and applications of GexSi1-x/Si strained-layer heterostructures

1986-09-01

R. People

This paper reviews recent advances in our current level of understanding of the physics underlying transport and optical properties of Ge <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> Si <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-x</inf> /Si strained-layer … This paper reviews recent advances in our current level of understanding of the physics underlying transport and optical properties of Ge <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> Si <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-x</inf> /Si strained-layer heterostructures. Included are discussions of critical (maximum) layer thicknesses, effects of coherency strain on the bandgaps of both Si and Ge <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> Si <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-x</inf> and the influence of layer strains on the band alignments of Ge <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> Si <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-x</inf> /Si strained-layer heterostructures. Transport studies will center on the modulation doping results of both n and p type heterostructures. Indeed, these earlier transport studies provided essential information which led to an understanding of the band-alignment in these strained layer heterostructures. Recent measurements of the indirect bandgap of Ge <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> Si <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-x</inf> strained layers on

Electrolytic Shaping of Germanium and Silicon

1956-03-01

A. Uhlir

Properties of electrolyte-semiconductor barriers are described, with emphasis on germanium. The use of these barriers in localizing electrolytic etching is discussed. Other localization techniques are mentioned. Electrolytes for etching germanium … Properties of electrolyte-semiconductor barriers are described, with emphasis on germanium. The use of these barriers in localizing electrolytic etching is discussed. Other localization techniques are mentioned. Electrolytes for etching germanium and silicon are given.

The Physics of Macropore Formation in Low Doped n‐Type Silicon

1993-10-01

V. Lehmann

Macropore formation in n‐type silicon is a self‐adjusting phenomenon characterized by a specific current density at the pore tip. At this specific current density, the dissolution reaction changes from the … Macropore formation in n‐type silicon is a self‐adjusting phenomenon characterized by a specific current density at the pore tip. At this specific current density, the dissolution reaction changes from the charge‐transfer‐limited to the mass‐transfer‐limited regime. The passivation of the pore walls in hydrofluoric acid is caused by a depletion of holes due to the n‐type doping of the substrate. Equations based on these findings are presented and allow us to precalculate the dimensions of the pores. The validity of the model and its mathematical description is verified in experiments. Pores of a depth up to the wafer thickness and aspect ratios of 250 were etched using this method.

Chemistry and Technology of Silicones

1968-01-01

Walter Noll

Porous Silicon Based Fuel Cell Type Alcohol Vapor Sensor

2025-06-19

Pinar Duzgun , Çiğdem Nuhoğlu , Sureyya Aydın Yüksel | Sensors and Actuators A Physical

A Fully Three-Dimensional Kinetic Particle-In-Cell Framework for Modeling Laser-Dielectric Interactions: Few-Cycle Pulse Damage

2025-06-16

Joseph R. Smith , Ziyao Su , Simin Zhang +3 more | High Power Laser Science and Engineering

Strain engineering of doped hydrogen passivated silicon quantum dots

2025-06-06

Swarnava Ghosh , Markus Eisenbach | Scientific Reports

Abstract Silicon quantum dots are nanomaterials that are attractive candidates for photovoltaic applications. Doping of these materials creates p-n junctions and is important for solar cells. In this work, we … Abstract Silicon quantum dots are nanomaterials that are attractive candidates for photovoltaic applications. Doping of these materials creates p-n junctions and is important for solar cells. In this work, we present a first-principles study of the coupled influence of doping and strain on the stability, energy gap, Fermi level, electronic density, and density of states of hydrogen-passivated silicon quantum dots. We find that the cohesive energy and the energy gap decrease with increasing quantum dot size and are strongly influenced by strain. Furthermore, the response to strain also depends on the size of the quantum dot and dopant type. We present expressions of cohesive energy and energy gap as power-law of size and polynomial dependence on strain. We also show that the Fermi energy increases with size for pristine and p-type doping but decreases with size for n-type doping. We also discuss the influence of strain and dopant type on the density of states and electron density of the quantum dots.

Implantable, Label‐Free NIR‐Based Porous Silicon Biosensor for Monitoring Biomarkers in Interstitial Fluid

2025-06-04

Pritam Sharma , Jann Harberts , Raquel Sánchez‐Salcedo +2 more | Advanced Sensor Research

Abstract The detection of biomarkers in interstitial fluid (ISF) holds significant promise for early disease diagnosis and monitoring. Porous silicon (pSi) offers a versatile platform for implantable biosensors due to … Abstract The detection of biomarkers in interstitial fluid (ISF) holds significant promise for early disease diagnosis and monitoring. Porous silicon (pSi) offers a versatile platform for implantable biosensors due to its biocompatibility, high surface area, and tunable properties. This study presents the development and characterization of a label‐free pSi biosensor featuring a near‐infrared (NIR) photonic microcavity (MC) that is implanted subcutaneously in a euthanized mouse to detect insulin in real time for proof of concept. The biosensor demonstrates specific insulin detection ability with a limit of detection (LOD) of 209 nM, exhibiting excellent consistency, reproducibility, and long‐term sensing performance. Furthermore, the biosensor demonstrates the capability to detect insulin spiked into plasma obtained from a healthy mouse. It is further reported that a simple and sensitive data analysis method, the effective shift in wavelength (ESW) method for measuring the shift in center wavelength of the photonic MC. This viable approach can be extended to other photonic biosensors where measurements are limited by the resolution of the spectrometer. The proposed approach lays the foundation for the development of pSi‐based implantable biosensors for real‐time continuous monitoring of clinically relevant biomarkers in vivo for chronic disease management.

Highly Bright Silicon Nanocrystal White Light‐Emitting Diodes With Luminance in Excess of 10000 cd m⁻2 (Laser Photonics Rev. 19(12)/2025)

2025-06-01

Fengyang Ma , Kaixin Liu , Zhongyao Yan +7 more | Laser & Photonics Review

Spatial correlation model for Si-rich SiGe alloys based on Raman spectra

2025-06-01

Ryo Yokogawa , Yuiha Maeda , Y. Ito +3 more | Japanese Journal of Applied Physics

Abstract We applied the spatial correlation model (SCM) to the analysis of the first-order optical phonon modes of silicon-germanium (SiGe) alloys. The SCM of SiGe was constructed on the basis … Abstract We applied the spatial correlation model (SCM) to the analysis of the first-order optical phonon modes of silicon-germanium (SiGe) alloys. The SCM of SiGe was constructed on the basis of the longitudinal optical phonon dispersion curves and applied to Raman spectra of bulk SiGe. We found that the proposed SCMs reproduce the Raman spectra with asymmetry of the first-order optical phonon modes of the bulk SiGe. The atomic arrangement of SiGe is supposed not to be completely random. There are differences in the linewidth (phonon lifetime) between each vibration mode (Si-Si, Si-Ge, and Ge-Ge modes) in the analysis using the SCM.

Enabling isolation of an intrinsically amorphous API using a mesoporous carrier-assisted particle engineering approach

2025-06-01

Tao Zhang , Weidong Ruan , Jie Gao +7 more | Journal of Pharmaceutical Sciences

Achieving high luminescence efficiency and optical gain of erbium ions (λ = 1540 nm) in a silicon nanocrystalline thin film by a combined approach

2025-06-01

Kaixin Liu , Fengyang Ma , Zhongyao Yan +6 more | Chinese Journal of Physics

Influence of Pre-deposition Temperature of Phosphorous Silicate Glass layers on the Formation of n+/n Junctions

2025-06-01

A. Djelloul , A. Boucheham , A. Marref +7 more | Semiconductors

Influence of Metal Type and Layer Thickness on Absorption of Optical Radiation by Profiled Si3N4/Me/Si3N4 Structures

2025-05-30

S. V. Kozodoev , A. I. Muhammad , В. В. Колос +1 more | Journal of Applied Spectroscopy

Effective Performance of Gold–Zirconia Photodetector Produced via Laser Energy Control Deposited on Porous Silicon

2025-05-29

Ruwaida T. Shbeeb , Falah A.-H. Mutlak | Plasmonics

Highly efficient electroluminescence from Si Quantum Dots/SiO2 multilayers Light-Emitting Devices Via Phosphorus/Boron co-doping and Surface Nano-structuring

2025-05-27

Junnan Han , Yuhao Wang , Jiaming Chen +6 more

Recycling of Waste Silicon Wafers for Semihydrogenation of Alkynes

2025-05-27

Takuya Shiroshita , Shingo Hasegawa , Yusuke Tanimura +2 more

Temperature-Dependent Photoluminescence of Surface-Passivated 2D-Layered Silicon Carbide Nanocrystals

2025-05-27

Naif S. Alharthi , Salim A. Thomas , Reed J. Petersen +4 more

High surface quality Y2SiO5 silicate-crystal waveguides etched by chlorine-based inductive coupled plasma reactive ion etching

2025-05-23

A. Talneau , M.K. Chan , Feriel Laourine +4 more

Among rare-earth ion-doped crystals that are of high interest for quantum technologies, yttrium orthosilicate [Y2SiO5 (YSO)] crystal has demonstrated the longest coherence times. Etching optical guiding structures enables the creation … Among rare-earth ion-doped crystals that are of high interest for quantum technologies, yttrium orthosilicate [Y2SiO5 (YSO)] crystal has demonstrated the longest coherence times. Etching optical guiding structures enables the creation of complex structures offering the advantage of technological scalability. We report on the dry etching of YSO crystal wafers performed by inductive coupled plasma (ICP) reactive ion etching. The material etching rate, the etch rate selectivity versus the material mask, and the etched side wall’s shape have been measured for various ICP process parameters and gas combinations including Ar-alone, Cl2:Ar, and Cl2:N2 plasma chemistry. These gas-combination choices have enabled identifying the etching mechanisms involved. Etching results have evidenced that Ar ions are the primary contributors for YSO etching, with Cl ions being also efficient, while Cl neutrals play a marginal role. ICP YSO etching is predominantly a physical process carried out by ions. Several ICP powers and RF powers have been investigated. The highest 80 nm/min etch rate is obtained under the Ar-alone plasma, but at the expense of trenching, while chlorine-based etching provides no trenching and smooth side walls. The choice of the dielectric material mask is also discussed.

Space-Charge Limited Schottky Diodes with Wide-Bandgap Thin-Film Oxide Heterojunctions

2025-05-20

Ji-Hun Lim

Transmission electron microscopy analysis of UV laser implanted gold nanoparticles and their influence on photoluminescence enhancement from silicon nanocrystals

2025-05-16

Lukas Janos Richter , Ulrich Roß , Michael Seibt +1 more

Abstract The photoluminescence of silicon nanocrystals is significantly enhanced via laser-based implantation of gold nanoparticles into silicon suboxide. This study is to explore in detail the nanoscale interactions between silicon … Abstract The photoluminescence of silicon nanocrystals is significantly enhanced via laser-based implantation of gold nanoparticles into silicon suboxide. This study is to explore in detail the nanoscale interactions between silicon nanocrystals embedded in the oxide matrix and gold nanoparticles through transmission electron microscopy. The influence of gold nanoparticle size and distance from the silicon nanocrystals is investigated and correlated with photoluminescence enhancement. A more than threefold enhancement in photoluminescence of silicon nanocrystals is observed, depending on the size and separation distance of the gold nanoparticles, demonstrating the efficiency of this straightforward and rapid laser-based method.

Color Centers in Silicon Carbide for Quantum Technologies

2025-05-14

Danial Shafizade

Ge and Core/Shell Ge/Al Quantum Dot Lattices in Amorphous SiC Matrix for Application in Photo- and Thermosensitive Devices

2025-05-08

Marija Tkalčević , Matej Bubaš , Jordi Sancho‐Parramon +7 more

Telecom Light-Emitting Diodes Based on Nanoconfined Self-Assembled Silicon-Based Color Centers

2025-05-07

Andreas Salomon , Johannes Aberl , Enrique Prado Navarrete +7 more

Silicon color centers (SiCCs) have recently emerged as potential building blocks for light emitters in Si photonics, quantum emitters with spin storage capabilities, and Si-based quantum repeaters. We have recently … Silicon color centers (SiCCs) have recently emerged as potential building blocks for light emitters in Si photonics, quantum emitters with spin storage capabilities, and Si-based quantum repeaters. We have recently developed a noninvasive method to engineer carbon-related SiCCs confined to ultrathin nanolayers within a pristine crystalline environment, which is of utmost importance for the photostability of SiCCs. Here, we demonstrate embedding these C-doping-based SiCCs into the only 9 nm wide intrinsic region of a p-i-n diode using the epitaxial self-assembly of color centers. We report electrically pumped light emission with an exponential increase in the intensity as a function of the driving current until saturation. We associate this property with the shift of quasi-Fermi-level position upon electrical driving, which simultaneously improves the spectral homogeneity of the engineered SiCCs. Despite the low employed growth temperatures, our study demonstrates the electrical control and driving of near-infrared emitters in high-quality silicon diodes, an essential milestone for advancing classical and quantum optoelectronics.

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Spatial ordering of excitons in the germanium/silicon nanosystems with germanium quantum dots

2025-05-07

Sergey I. Pokutnyi

Experimental and computational investigation of an ionic pathway to the formation of silicon sulphide in the interstellar medium

2025-05-06

Matteo Michielan , Luca Mancini , Daniela Ascenzi +6 more

Silicon is the eighth most abundant element of the Sun's photosphere and neighbourhood. Despite it being mostly trapped in dust grains, some Si-bearing molecules have been detected in several interstellar … Silicon is the eighth most abundant element of the Sun's photosphere and neighbourhood. Despite it being mostly trapped in dust grains, some Si-bearing molecules have been detected in several interstellar and circumstellar sources. Silicon sulphide (SiS) is considered a relevant tracer for shocked regions and some neutral-neutral reactions have been investigated to pinpoint its formation routes. In contrast, a detailed laboratory characterisation of the contribution of ion-molecule reactions is lacking. Here, we analyse the role of the Si+ H2S reaction as a source of protonated SiS. Furthermore, we characterise the conversion of protonated SiS into its neutral counterpart via a proton-transfer-reaction with ammonia (i.e. an additional process with respect to electron-ion recombination). The reaction of Si+ with H2S has been experimentally studied by measuring absolute cross-sections (CSs) and branching ratios (BRs), as a function of collision energy. Experiments have been supported by a theoretical investigation combining high-level electronic structure calculations of the multi-dimensional doublet potential energy surface (PES) of the SiH2S+ system with a kinetic investigation. This allowed us to derive BRs and channel-specific rate constants as a function of temperature in the 10-300 K range. Stereo-dynamical constraints on the total rate constants were modelled by introducing an energy threshold that is dependent on the relative orientation of the reagents. The main product of the reaction (with a BR in the range 95-98.6%) has been assigned to the SiSH^+ ion, with the support of theoretical calculations. Furthermore SiS^+ has also been detected as a minor product. From the total reactive CS, measured as a function of collision energy, rate constant as a function of temperature have been estimated, with values increasing with temperature from k= (at 10 K) to $ $ cm^3s^-1 (at 300 K), in contrast to capture model predictions, demonstrating an increase with decreasing temperature. The proton transfer reactions between SiSH^+ and NH3 is found to be efficient with a rate constant of $ $ cm^3s^-1 that does not depend on temperature. In addition to neutral-neutral reactions, the ionic route here proposed can contribute or even dominate the formation of SiS in protostellar shocked regions, where atomic Si released from grains can be easily converted into Si^+ due to its low ionisation energy.

Ultraviolet-photon emitted GeO2/Ge quantum dots fabricated using hot Ge+-ion implantation into SiO2 layer

2025-05-05

Tomohisa Mizuno , Hayato Ban , N. Tsunoda

Using simple hot Ge+-ion implantation into an SiO2 layer at a substrate temperature T, followed by post-N2 annealing at 850 °C for an annealing time tN, we successfully fabricated GeO2/Ge … Using simple hot Ge+-ion implantation into an SiO2 layer at a substrate temperature T, followed by post-N2 annealing at 850 °C for an annealing time tN, we successfully fabricated GeO2/Ge quantum dots (GeO2/Ge-QDs) embedded in the SiO2 layer. The Ge+ ion dose (DGe) was varied from 1 × 1015 to 6 × 1015 cm−2 at 400 ≤ T ≤ 800 °C. Using transmission electron microscopy (TEM) observation, the diameter (Φ) of GeO2/Ge-QDs and surface density (NQD) increased drastically as T and tN increased, because of the increase in the formation rate of the QDs at a higher T, resulting in 1.9 ≤ Φ ≤ 3.2 nm and 1 × 1012 ≤ NQD ≤ 3 × 1012 cm−2. TEM observation revealed the partially crystallized rutile-GeO2-QDs and Ge-QDs. Hard x-ray photoelectron spectroscopy also revealed Ge–O2 and Ge–Ge bonds, which verified the formation of both GeO2-QDs and Ge-QDs. We also verified photoluminescence (PL) of the QDs with ultra-violet peaks of higher and lower energy peaks at approximately 4.4 eV (NHI) and 3.2 eV (NLO), whose spectra were assumed to originate from the GeO2- and Ge-QDs, respectively, because the PL peak energies of NHI and NLO were nearly equal to the bandgaps of rutile GeO2 and approximately 1.5-nm Ge-QDs. The PL intensity increased drastically as T and tN increased, which was attributed to an increase in the surface area of the QDs. The PL peak energy of NHI was roughly proportional to Φ−2, which was attributed to the quantum confinement effects of the carriers.

Luminescence properties of Ge and Ge-Si structures on silicon-based microcavities

2025-05-05

X. R. Zhou , Ziyang Zhou , Wenqian Wu +3 more

Utilizing laser etching technology under specific laser parameters (laser energy 250 mJ, repetition rate 1 Hz, pulse width 30 ns, spot diameter 150 µm), single-crystal silicon was etched, followed by … Utilizing laser etching technology under specific laser parameters (laser energy 250 mJ, repetition rate 1 Hz, pulse width 30 ns, spot diameter 150 µm), single-crystal silicon was etched, followed by the deposition of materials onto silicon-based microcavity samples using the pulsed laser deposition method. The Ge-coated microcavity samples were characterized using SEM and EDS, revealing cluster formations at the edges of the microcavities with the presence of germanium within these clusters. Photoluminescence spectroscopy identified characteristic luminescence peaks due to transverse optical (TO) phonon vibrations at 695 nm in the Ge-coated microcavity samples. Subsequently, the Ge-coated microcavity samples were subjected to high-temperature annealing at 1000 °C. After annealing for 30 min, a sharp luminescence peak at 700 nm associated with Ge-O bonds was observed. Finally, a layer of Si was deposited over the Ge-coated samples using pulsed laser deposition, resulting in a Ge-Si bilayer structure. After annealing at 1000 °C, this bilayer structure exhibited two distinctive peaks at 700 nm and 940 nm, with the former being a sharp peak due to Ge-O bonds and the latter due to the formation of Si-Si bonds within the clusters.

Tailoring in‐Plane Permittivity Gradients by Shadow Mask Molecular Beam Epitaxy

2025-05-03

Shagorika Mukherjee , Sai Rahul Sitaram , Mingyu Yu +2 more

Abstract Infrared (IR) gradient permittivity materials are the potential building blocks of miniature IR‐devices such as an on‐chip spectrometer. The manufacture of materials with permittivities that vary in the horizontal … Abstract Infrared (IR) gradient permittivity materials are the potential building blocks of miniature IR‐devices such as an on‐chip spectrometer. The manufacture of materials with permittivities that vary in the horizontal plane is demonstrated using shadow mask molecular beam epitaxy in Si:InAs films. However, to be useful, the permittivity gradient needs to be of high crystalline quality and its properties need to be tunable. In this paper, it is shown that it can control the permittivity gradient length and steepness by varying the shadow mask thickness. Samples grown with similar growth parameters and with 200 and 500 µm mask thicknesses show permittivity gradient widths of 18 and 39 µm on the flat mesa on one side and 11 and 23 µm on the film slope on the other side, respectively. The gradient steepnesses are 23.3 and 11.3 cm −1 /µm on the flat mesa and 21.8 and 9.1 cm −1 /µm on the film slope, for samples made with the 200 and 500 µm masks, respectively. This work clearly shows the ability to control the in‐plane permittivity gradient in Si:InAs films, setting the stage for the creation of miniature IR devices.

Innovative process for the production high-purity zeolites to passivate silicon's surface and bulk to improve electrical parameters

2025-05-01

Wala Medfai , Marouan Khalifa , R. Benabderrahmane Zaghouani +2 more

Internal force-controlled (IFC) sonication with tunable conditions for the large-scale preparation of porous silicon nanoparticles

2025-05-01

Nong‐Moon Hwang , Seung Yeop Baek , Duk‐Yong Choi +2 more

Photonic sensor for selective Ticagrelor detection based on porous silicon Fabry-Pérot interferometer modified with molecularly imprinted co-polymer

2025-05-01

Abdelrahman M. Allam , Amr M. Mahmoud , Shereen A. Boltia +2 more

Revisiting the effect of point defects on the decay of the longitudinal optical mode in semiconductors

2025-05-01

J. Anaya

Influence of slab interfaces and modulation regime on isolation ratio in graphene space-time crystal slabs: towards high-performance isolation

2025-05-01

O Kang‐Hyok , Kwang‐Hyon Kim

Harnessing Nanoplasmonics: Design Optimization for Enhanced Optoelectronic Performance in Nanocrystalline Silicon Devices

2025-04-30

Mohsen Mahmoudysepehr , Siva Sivoththaman

Nanoplasmonic structures have emerged as a promising approach to address light trapping limitations in thin-film optoelectronic devices. This study investigates the integration of metallic nanoparticle arrays onto nanocrystalline silicon (nc-Si:H) … Nanoplasmonic structures have emerged as a promising approach to address light trapping limitations in thin-film optoelectronic devices. This study investigates the integration of metallic nanoparticle arrays onto nanocrystalline silicon (nc-Si:H) thin films to enhance optical absorption through plasmonic effects. Using finite-difference time-domain (FDTD) simulations, we systematically optimize key design parameters, including nanoparticle geometry, spacing, metal type (Ag and Al), dielectric spacer material, and absorber layer thickness. The results show that localized surface plasmon resonances (LSPRs) significantly amplify near-field intensities, improve forward scattering, and facilitate coupling into waveguide modes within the active layer. These effects lead to a measurable increase in integrated quantum efficiency, with absorption improvements reaching up to 30% compared to bare nc-Si:H films. The findings establish a reliable design framework for engineering nanoplasmonic architectures that can be applied to enhance performance in photovoltaic devices, photodetectors, and other optoelectronic systems.

Synthesis of Silicon-Germanium Film Alloys Based on Chemically Formed Porous Silicon Layers

2025-04-29

Nikita Grevtsov

Formation of silicon-germanium alloy films by electrochemically filling a porous silicon matrix with germanium and subjecting it to rapid thermal processing at 950 °C in argon flow is investigated. Low-porosity … Formation of silicon-germanium alloy films by electrochemically filling a porous silicon matrix with germanium and subjecting it to rapid thermal processing at 950 °C in argon flow is investigated. Low-porosity porous silicon layers are obtained using metal-assisted chemical etching of lightly-doped silicon wafers. It is shown that the alloy film formed in the employed temperature regime is always located on a residual porous underlayer. The difference in the thickness of the initial porous silicon layer determines not only the thickness of this underlayer, but also that of the alloy film itself, as well as its elemental composition. This behavior is attributed to the difference in the distribution of the temperature gradient, as heat transfer from the subsurface region is greatly complicated due to reduced thermal conductivity of thicker porous layers, causing it to be subjected to higher temperatures and leading to the growth of a thicker alloy layer with increased silicon contents. Assumingly, the presence of a porous underlayer can thermally and electrically insulate the alloy film from the monocrystalline wafer, eliminating the need to transfer the film to a dielectric substrate for subsequent use in thermoelectric converters and other electronic devices.

Nonbonding Electron Inversion‐Driven Structural Engineering: Synergistic Enhancement of Linear and Nonlinear Optical Properties

2025-04-29

Jia‐Xiang Zhang , Shenghua Zhou , Xin‐Tao Wu +2 more

Abstract The simultaneous optimization of large birefringence (Δn, a linear optical property) and strong second‐harmonic generation (SHG, a nonlinear optical (NLO) property) in a single crystal remains a significant challenge … Abstract The simultaneous optimization of large birefringence (Δn, a linear optical property) and strong second‐harmonic generation (SHG, a nonlinear optical (NLO) property) in a single crystal remains a significant challenge due to the inherently distinct structural requirements for these properties. Although nonbonding electrons have been extensively studied in oxides and chalcogenides, research has predominantly focused on their role along polar axes, leaving their influence along axes in tetrahedral stacking largely unexplored. Herein, we propose a nonbonding electron‐inversion strategy to overcome phase‐matching limitations in defect diamond‐like structures. By incorporating T2‐[Ga 4 S 10 ] supertetrahedral motifs, we successfully synthesized [Ba 4 Cl 2 ][CdGa 4 S 10 ] (space group: I ), which exhibits a 219% enhancement in Δn compared to the nonphase‐matching parent structure Cd 2 GaS 4 . The weakly bound nonbonding electrons, governed by atomic potentials, demonstrate strong SHG responses under optical fields. The compound [Ba 4 Cl 2 ][CdGa 4 S 10 ] not only achieves a broad transmission range (0.28–18.6 µm) and a high laser‐induced damage threshold (40.1 × AgGaS 2 ) but also optimally balances a wide bandgap ( E g = 3.58 eV) and a large SHG response (1.4 × AgGaS 2 ), representing one of the best‐performing Cd‐based materials to date. This work introduces the first phase‐matching design strategy based on nonbonding electron‐driven structure–property relationships, providing critical insights for the rational design of high‐performance NLO materials.