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Full-Text Articles in Physics
Microscopic Investigation Of Phonon Modes In Sige Alloy Nanocrystals, Shang-Fen Ren, Wei Cheng, Peter Y. Yu
Microscopic Investigation Of Phonon Modes In Sige Alloy Nanocrystals, Shang-Fen Ren, Wei Cheng, Peter Y. Yu
Faculty publications – Physics
Phonon modes in spherical silicon germanium alloy (SiGe) nanocrystals containing up to 1147 atoms (3.6 nm) have been investigated as a function of the Si concentration. Microscopic details of phonon modes, including phonon frequencies and vibrational amplitudes, phonon density-of-states are calculated directly from the dynamic matrices. In particular, the dependence of phonon frequency on the configuration (such as a different ratio of Si to Ge atoms), and location (surface or interior) of clusters of atoms in SiGe alloy nanocrystals have been investigated. Low frequency surface phonons that are related to the spheroidal and torsional modes of a continuum sphere are …
Calculations Of Surface Effects On Phonon Modes And Raman Intensities Of Ge Quantum Dots, Shang-Fen Ren, Wei Cheng
Calculations Of Surface Effects On Phonon Modes And Raman Intensities Of Ge Quantum Dots, Shang-Fen Ren, Wei Cheng
Faculty publications – Physics
Phonon modes and Raman intensities of Ge quantum dots (QDs) with two different types of surfaces, a free standing surface or a fixed surface, in a size range from five atoms to 7 nm in diameter, are calculated by using a microscopic valence force field model. The results are compared, and the effects of surfaces on phonon properties of QDs are investigated. It is found that phonon modes and Raman intensities of QDs with these two different types of surfaces have obvious differences which clearly reveal the effects of the surfaces of QDs. The calculated results agree with existing experimental …
Calculations On The Size Effects Of Raman Intensities Of Silicon Quantum Dots, Wei Cheng, Shang-Fen Ren
Calculations On The Size Effects Of Raman Intensities Of Silicon Quantum Dots, Wei Cheng, Shang-Fen Ren
Faculty publications – Physics
Raman intensities of Si quantum dots (QD's) with up to 11489 atoms (about 7.6 nm in diameter) for different scattering configurations are calculated. First, phonon modes in these QD's, including all vibration frequencies and vibration amplitudes, are calculated directly from the lattice-dynamic matrix by using a microscopic valence force field model combined with the group theory. Then the Raman intensities of these quantum dots are calculated by using a bond-polarizability approximation. The size effects of the Raman intensity in these QD's are discussed in detail based on these calculations. The calculations are compared with the available experimental observations. We are …