Raman Shift and Broadening in Stress-Minimized Ge Nanocrystals in Silicon Oxide Matrix

1999 ◽  
Vol 581 ◽  
Author(s):  
YX Jie ◽  
CHA Huan ◽  
ATS Wee ◽  
ZX Shen
Keyword(s):  
Silicon Oxide ◽  
Phonon Dispersion ◽  
Weighting Function ◽  
Rf Magnetron Sputtering ◽  
Raman Shift ◽  
Stress Effect ◽  
Phonon Confinement ◽  
Peak Broadening ◽  
Non Gaussian ◽  
Ge Nanocrystals

ABSTRACTGe nanocrystals (nc-Ge) embedded in silicon oxide films were synthesized using RF magnetron sputtering and post-annealing procedure. To minimize the stress effect and inhomogeneity, we intentionally lower the cooling rates and reduce the temperature gradient during annealing. Significant Raman shifts ranging from 2.0 to 5.8 cm−1 have been observed from samples annealed at different temperatures. The size-dependent shift and broadening is found to be in good agreement with the phonon confinement mode together with the Gaussian weighting function, and the isotropic T02 phonon dispersion relation introduced by Sasaki et al. The Raman spectra can also be well-fitted using peaks calculated from the phonon confinement model. The inhomogeneous Raman peak broadening from our samples annealed at lower temperatures are attributed to the non-Gaussian size distribution of Ge nanocrystals.

Phonon confinement in Ge nanocrystals in silicon oxide matrix

2011 ◽  
Vol 109 (3) ◽  
pp. 033107 ◽  
Author(s):  
Yiaxiong Jie ◽  
A. T. S. Wee ◽  
C. H. A. Huan ◽  
Z. X. Shen ◽  
W. K. Choi
Keyword(s):  
Silicon Oxide ◽  
Phonon Confinement ◽  
Oxide Matrix ◽  
Ge Nanocrystals

scholarly journals Carrier Storage in Ge Nanocrystals Grown on Silicon Oxide by a Two Step Dewetting / Nucleation Process

Nanocrystals ◽  
10.5772/10092 ◽  
2010 ◽  
Author(s):  
Abdelillah El ◽  
Michel Troyon ◽  
Karim Gacem ◽  
Quang-Tri Do
Keyword(s):  
Silicon Oxide ◽  
Nucleation Process ◽  
Ge Nanocrystals

Thermal Properties of Nanotubes and Nanowires With Acoustically Stiffened Surfaces

2011 ◽  
Author(s):  
Michael F. P. Bifano ◽  
Vikas Prakash
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Specific Heat ◽  
Phonon Dispersion ◽  
Thermal Conductance ◽  
Frequency Equation ◽  
Outer Diameter ◽  
Phonon Confinement ◽  
Maximum Increase ◽  
Acoustic Tuning

A core-shell elasticity model is employed to investigate the effect of a nanowire and nanotube’s increased surface moduli on specific heat, ballistic thermal conductance, and thermal conductivity as a function of temperature. Phonon confinement is analyzed using approximated phonon dispersion relations that result from solutions to the frequency equation of a vibrating rod and tube. The results indicate a maximum 10% decrease in lattice thermal conductivity and ballistic thermal conductance near 160 K for a 10 nm outer diameter nanotube with an inner diameter of 5 nm when the average Young’s Modulus of both the inner and outer free surfaces is increased by a factor of 1.53. In the presence of the acoustically stiffened surfaces, the specific heat of the nanotube is found to decrease by up to 20% at 160 K. Near room temperature, changes in thermal properties are less severe. In contrast, a 10 nm outer diameter nanowire composed of similar material exhibits up to a 12% maximum increase in thermal conductivity at 600 K, a 25% increase in ballistic thermal conductance at 400 K, and a 48% increase in specific heat at 470 K when its outer free surface is acoustically stiffened to the same degree. Our simplified model may be extended to investigate the acoustic tuning of nanowires and nanotubes by inducing surface stiffening or softening via appropriate surface chemical functionalization and coatings.

Photoluminescence and Structural Properties of Si Nanoparticles Embedded in SiO2 Matrix by Reactive RF Magnetron Sputtering

2007 ◽  
Vol 336-338 ◽  
pp. 2074-2076
Author(s):  
K. Ma ◽  
Jia You Feng
Keyword(s):  
Magnetron Sputtering ◽  
Structural Properties ◽  
Near Infrared ◽  
Silicon Oxide ◽  
Rf Magnetron Sputtering ◽  
Sio2 Matrix ◽  
Si Nanoparticles ◽  
Oxide Matrix ◽  
Reactive Rf Magnetron Sputtering ◽  
Deposited Films

In the present work, we investigate the photoluminescence (PL) and structural properties of Si nanoparticles embedded in SiO2 matrix. Si-rich silicon oxide (SRSO) films with Si concentration of 39% were synthesized by reactive RF magnetron sputtering. Annealing was performed at temperatures between 600°C and 1100°C in N2 ambient for 2h to precipitate Si nanoparticles from oxide matrix. Near infrared photoluminescence around 750nm can be clearly observed even in the as-deposited films, which indicates the existence of Si nanoparticles in films. The structural properties were analyzed by infrared absorption and Raman spectra. It is found that the structural properties strongly affect the PL properties of Si nanoparticles embedded in SiO2 matrix.

The Residual Stress Effect on Microstructure and Optical Property of ZnO Films produced by RF Sputtering

2004 ◽  
Vol 854 ◽  
Author(s):  
Sang Ryu ◽  
Youngman Kim
Keyword(s):  
Optical Property ◽  
Substrate Temperature ◽  
Laser Scanning ◽  
Rf Sputtering ◽  
Film Surface ◽  
Rf Magnetron Sputtering ◽  
Zno Films ◽  
Stress Effect ◽  
Processing Variables ◽  
Residual Stress Effect

ABSTRACTZnO films were produced on the Si(100) and sapphire(0001) wafers by RF magnetron sputtering in terms of processing variables such as substrate temperature and RF power. The stress in films was obtained from the Stoney's formula using a laser scanning device. The stress levels in the films showed the range from ∼40MPa to ∼-1100MPa depending on processing variables.SEM was employed to characterize the microstructure of the films. As the substrate temperature increased, the film surface became rougher and the films showed coarser grains. The optical property of the films was studied by PL measurements. At the highest substrate temperature 800°C the film exhibited sharper UV peaks unlike other conditions.

RBS, XRD, Raman and AFM Studies of Microwave Synthesized Ge Nanocrystals

2011 ◽  
Vol 1354 ◽  
Author(s):  
N Srinivasa Rao ◽  
A P Pathak ◽  
G Devaraju ◽  
V Saikiran ◽  
S V S Nageswara Rao
Keyword(s):  
Rutherford Backscattering Spectrometry ◽  
Rf Magnetron Sputtering ◽  
Silica Matrix ◽  
Raman Spectrometry ◽  
Force Microscopy ◽  
Microwave Annealing ◽  
Atomic Force ◽  
Scattering Spectra ◽  
Raman Scattering Spectra ◽  
Ge Nanocrystals

ABSTRACTGe nanocrystals embedded in silica matrix have been synthesized on Si substrate by co-sputtering of SiO2 and Ge using RF magnetron sputtering technique. The as-deposited films were subjected to microwave annealing at 800 and 9000C. Rutherford backscattering spectrometry (RBS) has been used to measure the Ge composition and film thickness. The structural characterization was performed by using X-ray diffraction (XRD) and Raman spectrometry. XRD measurements confirmed the formation of Ge nanocrystals. Raman scattering spectra showed a peak of Ge-Ge vibrational mode around 299 cm−1, which was caused by quantum confinement of phonons in the Ge nanocrystals. Surface morphology of the samples was studied by atomic force microscopy (AFM). Variation of nanocrystal size with annealing temperature has been discussed. Advantages of microwave annealing are explained in detail.

Atomic Contribution to Valence Band Density of States in Gallium Oxide and Silicon Oxide Nano Layered Films

2010 ◽  
Vol 297-301 ◽  
pp. 849-852
Author(s):  
Toshio Takeuchi ◽  
Jiro Nishinaga ◽  
Atsushi Kawaharazuka ◽  
Yoshiji Horikoshi
Keyword(s):  
Valence Band ◽  
Density Of States ◽  
Photoelectron Spectroscopy ◽  
Gallium Oxide ◽  
Silicon Oxide ◽  
Rf Magnetron Sputtering ◽  
X Ray ◽  
Analytical Technique ◽  
Sapphire Substrates ◽  
Atomic Contribution

High resolution X-ray photoelectron spectroscopy (XPS) is used to investigate the spectra of nanolayered films. Amorphous gallium oxide (Ga2O3)-silicon dioxide (SiO2) nanolayered thin films are grown using ultrahigh vacuum radio frequency (rf) magnetron sputtering on sapphire substrates at room temperature. Films are layered with 15-angstrom Ga2O3 oxide and 75-angstrom SiO2 for a total of 10 layers. Referring to atomic core levels, atomic contribution to valence band density of states is experimentally nominated. This analytical technique has particular applicability to the evaluation of the density of states with atomic contributions.

Interpolation of bathymetry data from the Sea of Galilee: A noise attenuation problem

Geophysics ◽  
2004 ◽  
Vol 69 (2) ◽  
pp. 608-616 ◽  
Author(s):  
Antoine Guitton ◽  
Jon Claerbout
Keyword(s):  
Gaussian Noise ◽  
Prediction Error ◽  
Weighting Function ◽  
Depth Map ◽  
Water Levels ◽  
Iteratively Reweighted Least Squares ◽  
Data Set ◽  
Depth Images ◽  
Ship Tracks ◽  
Non Gaussian

We process a bathymetry survey from the Sea of Galilee. This data set is contaminated with non‐Gaussian noise in the form of spikes inside the lake and at the track ends. There is drift on the depth measurements leading to vessel tracks in the preliminary depth images. The drift comes from different seasonal and human conditions during data acquisition, e.g., wind and water levels. We derive an inversion scheme that produces a much‐reduced noise map of the Sea of Galilee. This inversion scheme includes preconditioning and iteratively reweighted least squares with the proper weighting function to remove the non‐Gaussian noise. We remove the ship tracks by adding a modeling operator inside the inversion that accounts for the drift in the data. We then approximate the model covariance matrix with a prediction error filter that enhances details inside the lake. Unfortunately, the prediction error filter slightly degrades the frequency content of the final depth map. Our images of the Sea of Galilee show ancient shorelines and, inside the lake, rifting features.

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