Quantum confinement and thermal effects on the Raman spectra of Si nanocrystals

2009 ◽  
Vol 80 (19) ◽  
Author(s):  
Giuseppe Faraci ◽  
Santo Gibilisco ◽  
Agata R. Pennisi
Keyword(s):  
Raman Spectra ◽  
Thermal Effects ◽  
Quantum Confinement ◽  
Si Nanocrystals

Thermal effects on the Raman spectra of nanodiamonds

2011 ◽  
Vol 1282 ◽  
Author(s):  
Marc Chaigneau ◽  
Hugues A. Girard ◽  
Jean-Charles Arnault ◽  
Razvigor Ossikovski
Keyword(s):  
Raman Spectra ◽  
Thermal Effects ◽  
Laser Heating ◽  
Quantum Confinement ◽  
Laser Power ◽  
Heating Effect ◽  
Scattering Experiment ◽  
Quantum Confinement Effects ◽  
High Pressure High Temperature ◽  
Peak Assignment

ABSTRACTWe report on the influence of the laser heating effect, potentially present in a Raman scattering experiment, on the behaviour of carbon phonon lines in the spectra of nanodiamond particles. Aside from the laser power used in the experiment, the extent of the thermal effect in question depends also on the nanodiamonds origin (obtained through detonation and high pressure high temperature techniques) as well as on the nanoparticles size. Laser heating should be properly taken into account when discussing Raman spectra of carbonaceous species, in particular, prior to addressing peak assignment and possible quantum confinement effects.

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.

Laser Induced Etching for Generation of Si Nanocrystals and Spectroscopic Investigation of Morphology

2005 ◽  
Vol 23 ◽  
pp. 43-46
Author(s):  
H.S. Mavi ◽  
S. Rath ◽  
Arun Shukla
Keyword(s):  
Quantum Confinement ◽  
Silicon Nanocrystals ◽  
Laser Wavelength ◽  
Interconnected Network ◽  
Substrate Type ◽  
Argon Ion Laser ◽  
Si Nanocrystals ◽  
Ion Laser ◽  
Laser Induced Etching ◽  
Argon Ion

Laser-induced etching of silicon is used to generate silicon nanocrystals. The pore structure depends on the substrate type and etching laser wavelength. Porous silicon (PS) samples prepared by Nd:YAG laser (1.16 eV) etching of n-type substrate showed a fairly uniform and highly interconnected network of nearly circular pores separated by thin columnar boundaries, while no circular pits were produced by argon- ion laser (2.41 eV) etching under similar conditions. The size and size distribution of the nanocrystals are investigated by Raman and photoluminescence spectroscopies and analyzed within the framework of quantum confinement models.

Influence of the Dispersion of the Size of the Si Nanocrystals on their Emission Spectra

1994 ◽  
Vol 358 ◽  
Author(s):  
J. B. Khurgin ◽  
E. W. Forsythe ◽  
S. I. Kim ◽  
B. S. Sywe ◽  
B. A. Khan ◽  
...  
Keyword(s):  
Systematic Study ◽  
Quantum Confinement ◽  
Emission Spectra ◽  
Emission Peak ◽  
Nanocrystal Size ◽  
Pl Spectra ◽  
Si Nanocrystals ◽  
Average Size ◽  
Size Dispersion ◽  
Confinement Model

ABSTRACTA systematic study of the PL spectra of Si quantum nanocrystals in the SiO2 matrix has been performed. The results have been fitted to a quantum-confinement model that includes the nanocrystal size dispersion rather than a specific size of the nanocrystal. This serves as a strong confirmation of the confinement-induced nature of the PL. It has been shown that if the dispersion is taken into account, the position of the emission peak as well as the PL width can always be correlated with the average size of the nanocrystal.

Control of and Mechanisms for Room Temperature Visible light Emission from Silicon Nanostructures in SiO2 formed by Si+ Ion Implantation

1994 ◽  
Vol 358 ◽  
Author(s):  
T. Komoda ◽  
J.P. Kelly ◽  
A. Nejm ◽  
K.P. Homewood ◽  
P.L.F Hemment ◽  
...  
Keyword(s):  
Quantum Confinement ◽  
Room Temperature ◽  
Light Emission ◽  
Silicon Nanostructures ◽  
Two Phase ◽  
Population Distributions ◽  
Si Nanocrystals ◽  
Induced Defects ◽  
Irradiation Induced Defects ◽  
Si Ion Implantation

ABSTRACTImplantation of Si+ ions into thermal oxides grown on silicon has been used to synthesise a two phase structure consisting of Si nanocrystals in a SiO2 matrix. Various processing conditions have been used in order to modify the size and population distributions of the Si inclusions. Photoluminescence spectra have been recorded from samples annealed in nitrogen, forming gas and oxygen. Both red and blue shifts of the luminescence peaks have been observed. It is concluded that the photoluminescence is a consequence of the effects of quantum confinement but is also dependent on the presence of irradiation-induced defects or Si/SiO2 interface states.

Charge Retention in Single Silicon Nanocrystal Layers

2002 ◽  
Vol 737 ◽  
Author(s):  
Rishikesh Krishnan ◽  
Todd D. Krauss ◽  
Philippe M. Fauchet
Keyword(s):  
Silicon Dioxide ◽  
Amorphous Silicon ◽  
Quantum Confinement ◽  
Growth Direction ◽  
Scanning Transmission Electron Microscope ◽  
Amorphous Silicon Dioxide ◽  
Si Nanocrystals ◽  
Scanning Transmission ◽  
Non Volatile Memory ◽  
Electric Force Microscopy

ABSTRACTSilicon (Si) nanocrystals formed by controlled thermal crystallization of amorphous silicon dioxide (a-SiO2)/amorphous silicon (a-Si)/amorphous silicon dioxide (a-SiO2) layers hold considerable promise for application in non-volatile memory products and optoelectronic devices. The size of the nanocrystals is fixed by the thickness of the Si layer and strong quantum confinement is provided in the vertical (growth) direction by the insulating a-SiO2 layers. However, the extent of quantum confinement in the lateral dimensions remains to be established. Electron energy loss spectroscopy (EELS) measurements performed within a scanning transmission electron microscope (STEM) indicate that the nanocrystals are laterally isolated by approximately 2nm of a-SiO2. The confinement potential provided by this barrier is insufficient to localize carriers within a nanocrystal for prolonged durations and can permit quantum mechanical tunneling via wave function overlap between adjacent nanocrystals. Charge leakage kinetics within a sheet of Si nanocrystals was studied using electric force microscopy. Approximately 750 electrons were injected within a 100nm radius circular patch with an atomic force microscope cantilever. The entire charge dissipated from this area in 70min via lateral conduction routes. With a goal of localizing the injected charge and enhancing its retention time, the samples were subjected to relatively low temperature dry oxidation at 750°C. After 20 min of oxidation, retention times above 400 minutes were observed.

Thermal effects in Raman spectra of hexagonal boron nitride and nanotube-containing boron nitride soot

2006 ◽  
Vol 243 (13) ◽  
pp. 3316-3319 ◽  
Author(s):  
N. R. Arutyunyan ◽  
E. D. Obraztsova ◽  
M. Silly ◽  
P. Jaffrennou ◽  
B. Attal-Tretout ◽  
...  
Keyword(s):  
Boron Nitride ◽  
Raman Spectra ◽  
Thermal Effects ◽  
Hexagonal Boron Nitride

Effect of atmospheric oxidation on the electronic and photoluminescence properties of silicon nanocrystal

2000 ◽  
Vol 72 (1-2) ◽  
pp. 245-255 ◽  
Author(s):  
I. N. Germanenko ◽  
M. Dongol ◽  
Y. B. Pithawalla ◽  
M. Samy El-Shall ◽  
J. A. Carlisle
Keyword(s):  
Quantum Confinement ◽  
Blue Shift ◽  
Laser Vaporization ◽  
Photoluminescence Properties ◽  
Bonding Structure ◽  
Quantum Size ◽  
Si Nanocrystals ◽  
Crystalline Core ◽  
Si Nanoparticles ◽  
Significant Blue Shift

Web-like aggregates of coalesced Si nanocrystals produced by a laser vaporization-controlled condensation technique show luminescence properties that are similar to those of porous Si. The results are consistent with a quantum confinement mechanism as the source of the red photoluminescence (PL) in this system. The oxidized Si nanoparticles do not exhibit the red PL that is characteristic of the surface-oxidized Si nanocrystals. The nanoparticles are allowed to oxidize slowly, and the PL is measured as a function of the exposure time in air. A significant blue shift in the red PL peak is observed as a result of the slow oxidation process. The dependence of quantum size effects on the bonding structure is established by correlating the PL data with the photon-yield electronic structure measurements made at the Advanced Light Source. The results indicate that as the nanoparticles oxidize, the radius of the crystalline core decreases in size, which gives rise to a larger bandgap and consequently to the observed blue-shift in the PL band. The correlation between the PL, SXF, and NEXAFS results provides further support for the quantum confinement mechanism as the origin of the visible PL in Si nanocrystals.

Evidence of quantum confinement effects on interband optical transitions in Si nanocrystals

2010 ◽  
Vol 82 (4) ◽  
Author(s):  
M. I. Alonso ◽  
I. C. Marcus ◽  
M. Garriga ◽  
A. R. Goñi ◽  
J. Jedrzejewski ◽  
...  
Keyword(s):  
Quantum Confinement ◽  
Optical Transitions ◽  
Confinement Effects ◽  
Quantum Confinement Effects ◽  
Si Nanocrystals

scholarly journals X-Ray Absorption Spectroscopy from H-Passivated Porous Si and Oxidized Si Nanocrystals

1994 ◽  
Vol 375 ◽  
Author(s):  
S. Schuppler ◽  
S. L. Friedman ◽  
M. A. Marcus ◽  
D. L. Adler ◽  
Y.-H. Xie ◽  
...  
Keyword(s):  
Fine Structure ◽  
Quantum Confinement ◽  
Ir Absorption ◽  
X Ray ◽  
Coordination Numbers ◽  
Absorption Fine ◽  
Visible Luminescence ◽  
Si Nanocrystals ◽  
Wide Range ◽  
X Ray Absorption

AbstractQuantum confinement in nanoscale Si structures is widely believed to be responsible for the visible luminescence observed from anodically etched porous silicon (por-Si), but little is known about the actual size or shape of these structures. Extended x-ray absorption fine structure data from a wide variety of por-Si samples show significantly reduced average Si coordination numbers due to the sizable contribution of surface-coordinated H. (The H/Si ratios, as large as 1.2, were independently confirmed by ir-absorption and α-recoil measurements.) The Si coordinations imply very large surface/volume ratios, enabling the average Si structures to be identified as crystalline particles (not wires) whose dimensions are typically <15 Å. Comparison of the size-dependent peak luminescence energies with those of oxidized Si nanocrystals, whose shapes are known, shows remarkable agreement. Furthermore, near-edge x-ray absorption fine structure measurements of the nanocrystals shows the outer oxide and interfacial suboxide layers to be constant over a wide range of nanocrystal sizes. The combination of these results effectively rules out surface species as being responsible for the observed visible luminescence in por-Si, and strongly supports quantum confinement as the dominant mechanism occurring in Si particles which are substantially smaller than previously reported or proposed.

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