Theory of the Physical Properties of Si Nanocrystals

1994 ◽  
Vol 358 ◽  
Author(s):  
M. Lannoo ◽  
C. Delerue ◽  
G. Allan ◽  
E. Martin
Keyword(s):  
Porous Silicon ◽  
Radiative Recombination ◽  
Surface Defects ◽  
Stokes Shift ◽  
Optical Excitation ◽  
Recombination Time ◽  
Si Nanocrystals ◽  
Donor And Acceptor ◽  
Electron Hole Pair ◽  
Level Of Understanding

ABSTRACTThis paper reviews calculations concerning several aspects of silicon crystallites and their relevance for porous silicon. This begins with the optical properties of perfect crystallites: gap versus size, radiative recombination time, relative importance of phonon assisted transitions. A second part is devoted to the determination of the excitonic exchange splitting and of the Stokes shift which are found to bring a similar contribution (∼10 to 20 meV). The effect of surface defects like dangling bonds is then investigated with their contribution to the recombination time. The Auger non radiative recombination time is also calculated and found to be short (∼1 nsec). This is confirmed by some experiments on porous silicon which show a saturation effect of the photoluminescence under intense optical excitation or under cathodic polarization in aqueous solution, Auger recombination preventing the existence of more than one electron-hole pair per crystallite. Donor and acceptor impurities are studied in detail (screening of Coulomb potential, notion of ionization energy) with the conclusion that they are ionized. A final discussion shows the present level of understanding and identifies problems remaining to be solved.

The Origin Of Light Emission From Porous Silicon

1997 ◽  
Vol 486 ◽  
Author(s):  
M. Ben-Chorin ◽  
H. Heckler ◽  
D. Kovalev ◽  
B. Averboukh ◽  
G. Polisski ◽  
...  
Keyword(s):  
Porous Silicon ◽  
Radiative Recombination ◽  
Light Emission ◽  
Hole Burning ◽  
Si Nanocrystals ◽  
Quantum Confined ◽  
Viable Model

AbstractWe report on luminescence hole burning experiments, which prove that radiative recombination between quantum confined states is the only viable model for the mechanism of the light emission from porous silicon. We find that more than 90% of the luminescence originates from quantum confined states inside the Si nanocrystals.

An Intrinsic Model for Radiative Recombination in Porous Silicon

1991 ◽  
Vol 256 ◽  
Author(s):  
Mark S. Hybertsen
Keyword(s):  
Matrix Element ◽  
Porous Silicon ◽  
Radiative Recombination ◽  
Energy Shift ◽  
Short Length ◽  
Length Scale ◽  
Dipole Matrix Element ◽  
Light Emitting ◽  
Recombination Time

A microcrystalline model for the light emitting portion of porous silicon is outlined. Confinement to a short length scale induces an effective direct dipole matrix element for radiative recombination. The radiative recombination time is strongly size (hence confinement induced energy shift) dependent, and in the microsecond regime for blue shifts of ˜1 eV. Trends and comparison to experiment are discussed.

Formation of Luminescent Si Nanocrystals by High-Temperature Annealing of Ion-Beam-Sputtered Si/SiO2 Multilayers

2003 ◽  
Vol 775 ◽  
Author(s):  
Suk-Ho Choi ◽  
Jun Sung Bae ◽  
Kyung Jung Kim ◽  
Dae Won Moon
Keyword(s):  
Quantum Confinement ◽  
Radiative Recombination ◽  
Ion Beam ◽  
Quantum Confinement Effect ◽  
Visible Range ◽  
Ion Beam Sputtering ◽  
Transmission Electron ◽  
Si Nanocrystals ◽  
Beam Sputtering ◽  
Microscopy Images

AbstractSi/SiO2 multilayers (MLs) have been prepared under different deposition temperatures (TS) by ion beam sputtering. The annealing at 1200°C leads to the formation of Si nanocrystals in the Si layer of MLs. The high resolution transmission electron microscopy images clearly demonstrate the existence of Si nanocrystals, which exhibit photoluminescence (PL) in the visible range when TS is ≥ 300°C. This is attributed to well-separation of nanocrystals in the higher-TS samples, which is thought to be a major cause for reducing non-radiative recombination in the interface between Si nanocrystal and surface oxide. The visible PL spectra are enhanced in its intensity and are shifted to higher energy by increasing TS. These PL behaviours are consistent with the quantum confinement effect of Si nanocrystals.

High Temperature Annealing Behaviors of Luminescent Siox:H Films

1999 ◽  
Vol 560 ◽  
Author(s):  
Zhixun Ma ◽  
Xianbi Xiang ◽  
Shuran Sheng ◽  
Xianbo Liao ◽  
Chunlin Shao ◽  
...  
Keyword(s):  
High Temperature ◽  
Absorption Edge ◽  
Optical Transition ◽  
Stokes Shift ◽  
Transition Process ◽  
Ir Absorption ◽  
High Temperature Annealing ◽  
Force Microscopy ◽  
Atomic Force ◽  
Si Nanocrystals

ABSTRACTThe effects of high temperature annealing on the microstructure and optical properties of luminescent SiOx:H films have been investigated. Micro-Raman scattering and IR absorption, in combination with atomic force microscopy (AFM), provide evidence for the existence of both a-Si clusters in the as-grown a-SiOx:H and Si nanocrystals in the 1170°C annealed films. The dependence of optical coefficients (μ) on photon energy (hv) near the absorption edge (Eg) is found to follow the square root law: (μhv)½ μ (Eg – hv), indicating that nano-Si embedded in Si02 is still an indirect material. A comparison of the deduced absorption edge with the PL spectra shows an obvious Stokes shift, suggesting that phonons should be involved in the optical transition process.

Comparative Optical Studies of Chemically Synthesized Silicon Nanocrystals

1996 ◽  
Vol 452 ◽  
Author(s):  
Gildardo R. Delgado ◽  
Howard W.H. Lee ◽  
Susan M. Kauzlarich ◽  
Richard A. Bley
Keyword(s):  
Porous Silicon ◽  
Silicon Nanocrystals ◽  
Surface Passivation ◽  
Theoretical Calculations ◽  
Dominant Role ◽  
Blue Emission ◽  
Surface States ◽  
Si Nanocrystals ◽  
Optical And Electronic Properties ◽  
Passivation Layers

AbstractWe studied the optical and electronic properties of silicon nanocrystals derived from two distinct fabrication procedures. One technique uses a controlled chemical reaction. In the other case, silicon nanocrystals are produced by ultrasonic fracturing of porous silicon layers. We report on the photoluminescence, photoluminescence excitation, and absorption spectroscopy of various size distributions derived from these techniques. We compare the different optical properties of silicon nanocrystals made this way and contrast them with that observed in porous silicon. Our results emphasize the dominant role of surface states in these systems as manifested by the different surface passivation layers present in these different fabrication techniques. Experimental absorption measurements are compared to theoretical calculations with good agreement. Our results provide compelling evidence for quantum confinement in both types of Si nanocrystals. Our results also indicate that the blue emission from very small Si nanocrystals corresponds to the bandedge emission, while the red emission arises from traps.

Photoluminescence from n-(p-) type impurity doped Si nanocrystals

2000 ◽  
Vol 638 ◽  
Author(s):  
Minoru Fujii ◽  
Atsushi Mimura ◽  
Shinji Hayashi ◽  
Dmitri Kovalev ◽  
Frederick Koch
Keyword(s):  
Free Electrons ◽  
Electron Hole ◽  
P Concentration ◽  
Si Nanocrystals ◽  
Donor And Acceptor ◽  
Impurity Doped ◽  
Pl Intensity ◽  
B Doping ◽  
Three Body ◽  
P Type

AbstractEffects of impurity (P and B) doping on the photoluminescence (PL) properties of Si nanocrystals (nc-Si) in SiO2 thin films are studied. It is shown that with increasing P concentration, PL intensity first increases and then decreases. In the P concentration range where PL intensity increases, quenching of the defect-related PL is observed, suggesting that dangling-bond defects are passivated by P doping. On the other hand, in the range where PL intensity decreases, optical absorptiondue to the intravalley transitions of free electrons generated by P doping appears. The generation of free electrons andthe resultant three-body Auger recombination of electron-hole pairs is considered to be responsible for theobserved PL quenching. In the case of B doping, the behavior is much different. With increasing B concentration, PL intensity decreases monotonously. By combining the results obtained for P and B doped samples, theeffects of donor and acceptor impurities on the PL properties of nc-Si are discussed.

The Oxidation Behavior of Silicon Nanocrystals in the Submonolayer Region

1997 ◽  
Vol 486 ◽  
Author(s):  
J. Diener ◽  
M. Ben-Chorin ◽  
D. I. Kovalev ◽  
G. Polisski ◽  
F. Koch
Keyword(s):  
Fourier Transform ◽  
Infrared Spectroscopy ◽  
Porous Silicon ◽  
Silicon Nanocrystals ◽  
Oxidation Behavior ◽  
Surface Oxidation ◽  
Square Root ◽  
Mesoporous Silicon ◽  
Si Nanocrystals ◽  
Evolution Of Oxygen

AbstractFourier transform infrared spectroscopy is used to determine the time evolution of oxygen incorporation onto the surface of silicon nanocrystals. Oxygen concentrations up to one monolayer are investigated. The temporal progress of surface oxidation of Si nanocrystals in porous silicon shows a linear dependence on the square root of the oxidation time. This is similar to the oxidation of bulk Si and mesoporous silicon.

Influence of Te doping in InGaAsSb epilayers on the non-radiative recombination time studied by the photoacoustic technique

2005 ◽  
Vol 125 ◽  
pp. 403-405
Author(s):  
M. L. Gomez-Herrera ◽  
I. Reich ◽  
P. Rodríguez-Fragoso ◽  
A. Cruz-Orea ◽  
F. Sanchez-Sinencio ◽  
...  
Keyword(s):  
Radiative Recombination ◽  
Photoacoustic Technique ◽  
Recombination Time

Photoluminescence Study of Radiative Recombination in Porous Silicon

1993 ◽  
Vol 298 ◽  
Author(s):  
Chun Wang ◽  
Franco Gaspari ◽  
Stefan Zukotynski
Keyword(s):  
Porous Silicon ◽  
Excited States ◽  
Ground State ◽  
Radiative Recombination ◽  
Single Electron ◽  
Photoluminescence Study ◽  
Recombination Centre ◽  
Electron Center ◽  
Recombination Centers

AbstractPhotoluminescence has been studied in porous silicon. Two types of radiative recombination centers have been identified. One gives rise to luminescence at about 820 nm and is believed to be related to Si-H bonds. The second gives rise to luminescence at about 770 nm and is likely associated with S-O bonds. Above about 20K radiative recombination is assisted by excited states of the recombination centre located about 10 meV above the ground state. The Si-H recombination centre is a single electron center whereas the Si-O center appears to be a multi-electron center.

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