Breakdown of thek-Conservation Rule in Si Nanocrystals

1998 ◽  
Vol 81 (13) ◽  
pp. 2803-2806 ◽  
Author(s):  
D. Kovalev ◽  
H. Heckler ◽  
M. Ben-Chorin ◽  
G. Polisski ◽  
M. Schwartzkopff ◽  
...  
Keyword(s):  
Si Nanocrystals ◽  
Conservation Rule

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.

Synthesis and size control of Si nanocrystals by SiO/SiO2 superlattices and Er doping

2002 ◽  
Vol 737 ◽  
Author(s):  
J. Heitmann ◽  
D. Kovalev ◽  
M. Schmidt ◽  
L.X. Yi ◽  
R. Scholz ◽  
...  
Keyword(s):  
Phase Separation ◽  
Crystal Size ◽  
Radiative Lifetime ◽  
Size Control ◽  
Luminescence Signal ◽  
Er Doping ◽  
Size Dependent ◽  
Transmission Electron ◽  
Si Nanocrystals ◽  
Ultrathin Layers

ABSTRACTThe synthesis of nc-Si by reactive evaporation of SiO and subsequent thermal induced phase separation is reported. The size control of nc-Si is realized by evaporation of SiO/SiO2 superlattices. By this method an independent control of crystal size and density is possible. The phase separation of SiO into SiO2 and nc-Si in the limit of ultrathin layers is investigated. Different steps of this phase separation are characterized by photoluminescence, infrared absorption and transmission electron microscopy measurements. The strong room temperature luminescence of nc-Si shows a strong blueshift of the photoluminescence signal from 850 to 750 nm with decreasing crystal size. Several size dependent properties of this luminescence signal, like decreasing radiative lifetime and increasing no-phonon transition properties with decreasing crystal size are in good agreement with the quantum confinement model. Er doping of the nc-Si shows an enhancement of the Er luminescence at 1.54 μm by a factor of 5000 compared to doped SiO2 layers. The decreasing transfer time for the nc-Si to Er transition with decreasing crystal size can be understood as additional proof of increasing recombination probability within the nc-Si for decreasing crystal size.

scholarly journals Derivation of Luminescent Mesoporous Silicon Nanocrystals from Biomass Rice Husks by Facile Magnesiothermic Reduction

Nanomaterials ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 613
Author(s):  
Sankar Sekar ◽  
Sejoon Lee
Keyword(s):  
Brown Rice ◽  
Total Pore Volume ◽  
Cost Effective ◽  
High Porosity ◽  
Magnesiothermic Reduction ◽  
Rice Husks ◽  
Average Pore ◽  
Efficient Catalyst ◽  
Mesoporous Silicon ◽  
Si Nanocrystals

High-quality silicon (Si) nanocrystals that simultaneously had superior mesoporous and luminescent characteristics were derived from sticky, red, and brown rice husks via the facile and cost-effective magnesiothermic reduction method. The Si nanocrystals were confirmed to comprise an aggregated morphology with spherical nanocrystals (e.g., average sizes of 15–50 nm). Due to the surface functional groups formed at the nanocrystalline Si surfaces, the Si nanocrystals clearly exhibited multiple luminescence peaks in visible-wavelength regions (i.e., blue, green, and yellow light). Among the synthesized Si nanocrystals, additionally, the brown rice husk (BRH)-derived Si nanocrystals showed to have a strong UV absorption and a high porosity (i.e., large specific surface area: 265.6 m2/g, small average pore diameter: 1.91 nm, and large total pore volume: 0.5389 cm3/g). These are indicative of the excellent optical and textural characteristics of the BRH-derived Si nanocrystals, compared to previously reported biomass-derived Si nanocrystals. The results suggest that the biomass BRH-derived Si nanocrystals hold great potential as an active source material for optoelectronic devices as well as a highly efficient catalyst or photocatalyst for energy conversion devices.

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.

Theoretical modeling of excitation and de-excitation processes of Er in SiO2 with Si nanocrystals

2006 ◽  
Vol 121 (2) ◽  
pp. 222-225 ◽  
Author(s):  
A.A. Prokofiev ◽  
A.S. Moskalenko ◽  
I.N. Yassievich
Keyword(s):  
Theoretical Modeling ◽  
Si Nanocrystals ◽  
Excitation Processes

Structure Study of Si Nanocrystals Formed by Electron-Induced Reduction of SiO2at High Temperature

1999 ◽  
Vol 38 (Part 1, No. 12B) ◽  
pp. 7140-7143 ◽  
Author(s):  
Masaki Takeguchi ◽  
Kazuo Furuya ◽  
Kazuhiro Yoshihara
Keyword(s):  
High Temperature ◽  
Structure Study ◽  
Si Nanocrystals
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