Strain Effect on Crystalline and Nanoscale Silicon Solids

• Main Authors: Hsiao-Chun Huang, 黃筱鈞
• Other Authors: Chee-Wee Liu
• Format: Others
• Language: en_US
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/16310812331820266739

碩士 === 國立臺灣大學 === 電子工程學研究所 === 93 === In this thesis, we investigate the physical phenomena of crystalline and nanoscale silicon solids under strain with models and simulations. For crystalline silicon solids, we first investigate strain effect on Raman shifts, then we investigate carrier mobility under orthorhombic strain, after that we investigate electron mobility under tensile strain when electrons are confined in inversion channel and quantum effect is inevitable. For nanoscale silicon solids, we first investigate in equilibrium condition, the degree of deformation under strain and its physical origins; then we investigate in non-equilibrium condition, the change of electrical properties under strain and its physical origins. Analyzing Raman red-shift is a good approach to determine the degree of tensile strains in the strained silicon epilayer. We propose a simple spring model, taking second derivatives of Harrison’s total energy to obtain the prediction for Raman red-shift. Carrier mobility in orthorhombically strained silicon is different than that of conventional planar tensile/compressive strained silicon. We incorporate the changes into bandstructure calculations, extract functions we need to calculate carrier mobility, then we obtain both electron and hole mobilities. When electron motion is confined in the inversion layer, the model for mobility needs to be modified. We use two-dimensional electron gas model to describe electron mobility, then we incorporate energy level shifts due to strain into the model, then we obtain electron mobility enhancement under various degrees of strains. We also use the simulation program, Gaussian, to simulate nanoscale silicon clusters’ morphology under strain. We have found that surface hydrogen plays a dominant role in defining the systems’ morphology, determining the stability of the systems and the behavior of deformation. Finally, we use the simulation program, TranSIESTA-C, to simulate nanoscale silicon atomic wire’s electrical properties under strain. We propose explanations for the change of electrical current under strains by analyzing transmission spectrum and MPSH (Molecular Projected Self-Consistent Hamiltonian) eigenstates.