應力於結晶與奈米級矽固體之作用

Strain Effect on Crystalline and Nanoscale Silicon Solids

黃筱鈞(Hsiao-Chun Huang)

指導教授 ： 劉致為

國立臺灣大學/電機資訊學院/電子工程學研究所/碩士(2005年)

https://doi.org/10.6342/NTU.2005.10113

摘要

本論文中，我們利用模型和模擬討論了結晶和奈米級矽固體受應力後的物理現象。對結晶矽固體我們首先討論受應力後的拉曼現象，接著討論斜方應力下載子遷移速度，再討論當電子受限在反轉層通道中、量子效應及張力下的電子遷移速度；對奈米級矽固體我們首先討論平衡狀態下，受應力後形變的程度和其物理來源，接著討論非平衡狀態下，受應力後電性的變化和其物理來源。
拉曼紅移是用來判斷應變矽受應力程度很好的方法。我們提出簡單的彈簧模型，兩次微分哈利森能量後我們獲得拉曼紅移的預測。
受斜方應力的矽固體之載子遷移速度和傳統平面伸展/壓縮應力之載子遷移速度有不同的變化。我們將此變化代入能帶計算中，再從能帶中獲得計算載子遷移速度所需的函數，最後計算出電子與電洞的遷移速度。
當電子的運動被限制在反轉層中，遷移速度的模型需要加以修正。我們利用二維電子氣的模型來描述電子遷移速度，再將受應力後能階的變化代入模型中，最後獲得不同應力程度下電子遷移速度增進的變化。
我們也利用高斯模擬軟體模擬奈米級矽群集受應力後的形態變化。我們發現表面氫決定了系統的穩定和形變行為。
最後我們用虛擬奈米實驗室模擬軟體模擬奈米級矽原子線受應力後的電性變化。我們利用分析傳輸譜和分子投影自洽漢彌頓的特徵態提出應力下電流變化的解釋。

關鍵字

應力 ； 拉曼現象 ； 載子遷移速度 ； 表面氫 ； 虛擬奈米實驗室

並列摘要

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.

並列關鍵字

strain ； Raman effect ； carrier mobility ； surface hydrogen ； TranSIESTA-C

參考文獻

[2] P. N. Keating, Phys. Rev, 145, 637 (1966).

[3] H. Rucker and M. Methfessel, Phys. Rev. B, 52, 11059 (1995)

[4] D. J. Lockwood and J.–M. Baribeau, Phys. Rev. B, 45, 8565 (1992).

[5] Walter A. Harrison, ”Electronic Structure and the Properties of Solids”, pp. 167-170, 1980.

[6] Walter A. Harrison, Phys. Rev. B, 23, 5230 (1981)