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Study of Strain Relaxation Mechanisms of Semiconductor Nanostructures by means of Atomistic Simulation

原子模拟研究半导体纳米结构的应变弛豫机制

基本信息

批准号：
12650074
负责人：
SHINTANI Kazuhito
金额：
$ 1.34万
依托单位：
The University of Electro-Communications
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2001
项目状态：
已结题

项目摘要

1. How the behavior of a Si adatom or a Ge adatom deposited on the Si substrate and the morphology of the deposited layers in the initial period depend on the substrate temperature was investigated by the molecular-dynamics simulations with the Stillinger-Weber potential and the Tersoff one. For Si/Si homo-deposition processes, it was concluded that (1) the deposited layers form an amorphous structure at 300K and 400K, (2) the deposited atoms construct the alternately perpendicular dimer rows in the successive atomic layers to form an epitaxial structure at 700K and 1000K, which agrees with experimental results, (3) the ranges of the trajectories of a single deposited atom at 300K and 400K do not extend beyond, those at 500K are of the order of, and those at 700K and 1000K extend beyond the length between the nearest-neighbor atoms at the substrate surface, which corresponds with the different morphologies of the deposited layers at the temperatures. For Ge/Si hetero-deposition process … More es, it was elucidated that (4) at 1000K, the deposited layers with the deposition energy 0.2eV grow in the layer-by-layer mode until the initial two to four monolayers are deposited, and then the growth mode changes into the amorphous one while the deposited layers form amorphous stractures in the other conditions.2. The temperature dependence of the strain distributions within Si/Ge/Si quantum dot structures was investigated using the molecular-dynamics simulation with the Tersoff potential, and the phonon densities of states for the optical mode were obtained. It was concluded that (1) the strain distributions within quantum dots computed by the molecular-dynamics method, at finite temperatures qualitatively agree with those computed by the conjugate-gradient method although the normal strain components perpendicular to the base of the quantum dots to the former are larger than those in the latter, and that (2) the positions of the peaks of the phonon densities of states for the optical mode in the quantum dots shift from those in bulk crystals3. The mechanical properties of carbon naotubes were investigated by the molecular-dynamics simulation. The interaction between carbon atoms were calculated by using the Brenner potential. The Poisson's ratios and the Young's modulus were obtained for the naotubes models with the same diameter and with six chiral angles. It was conluded that (1) the Poisson's ratios of naotubes depend on their chiral angles, (2) the Young's modulus of nanotubes does not depends on their chiral angles, and (3)the elastic region in the deformations of nanotubes are extremely broad. Less

1. 利用Stillinger-Weber势和Tersoff势进行分子动力学模拟，研究了沉积在Si衬底上的Si和Ge吸附原子的行为以及沉积层在初始阶段的形貌对衬底温度的影响。对于Si/Si均相沉积工艺，得出：(1)沉积层在300K和400K时形成无定形结构；(2)沉积原子在700K和1000K时在连续的原子层中形成交替垂直的二聚体行，形成外延结构，这与实验结果一致；(3)单个沉积原子在300K和400K时的轨迹范围不超过，500K时的轨迹约为；在700K和1000K温度下，衬底表面最近邻原子之间的长度超出了衬底表面最近邻原子之间的长度，这与不同温度下沉积层的不同形貌相对应。对于Ge/Si异质沉积过程，进一步阐明了(4)在1000K条件下，沉积能量为0.2eV的沉积层以逐层生长模式生长，直到最初的2 ~ 4层单层沉积，然后转变为非晶生长模式，而在其他条件下沉积层形成非晶结构。利用Tersoff势的分子动力学模拟研究了Si/Ge/Si量子点结构中应变分布的温度依赖性，并获得了光模态声子密度。得出(1)应变分布在量子点分子动力学计算的方法,在有限的温度下定性同意共轭梯度方法虽然计算的正应变分量垂直于量子点的基础,前者大于后者,,(2)声子密度的峰值的位置状态量子点的光学模式转变与批量crystals3。采用分子动力学模拟方法研究了碳纳米管的力学性能。利用布伦纳势计算了碳原子间的相互作用。得到了具有相同直径和六个手性角的纳米管模型的泊松比和杨氏模量。结果表明：(1)纳米管的泊松比与纳米管的手性角有关；(2)纳米管的杨氏模量与纳米管的手性角无关；(3)纳米管变形中的弹性区域非常宽。少