激光辐射在元素半导体表面形成纳米锥的两阶段模型。

Two-stage model of nanocone formation on a surface of elementary semiconductors by laser radiation.

机构信息

Institute of Technical Physics, Riga Technical University, Azenes iela 14/24, Riga LV-1048, Latvia.

出版信息

Nanoscale Res Lett. 2012 Jul 31;7(1):428. doi: 10.1186/1556-276X-7-428.

DOI:10.1186/1556-276X-7-428

PMID:22849869

原文链接:https://pmc.ncbi.nlm.nih.gov/articles/PMC3534381/

Abstract

In this work, we study the mechanism of nanocone formation on a surface of elementary semiconductors by Nd:YAG laser radiation. Our previous investigations of SiGe and CdZnTe solid solutions have shown that nanocone formation mechanism is characterized by two stages. The first stage is characterized by formation of heterostructure, for example, Ge/Si heterostructure from SiGe solid solutions, and the second stage is characterized by formation of nanocones by mechanical plastic deformation of the compressed Ge layer on Si due to mismatch of Si and Ge crystalline lattices. The mechanism of nanocone formation for elementary semiconductors is not clear until now. Therefore, the main goal of our investigations is to study the stages of nanocone formation in elementary semiconductors. A new mechanism of p-n junction formation by laser radiation in the elementary semiconductor as a first stage of nanocone formation is proposed. We explain this effect by the following way: p-n junction is formed by generation and redistribution of intrinsic point defects in temperature gradient field - the thermogradient effect, which is caused by strongly absorbed laser radiation. According to the thermogradient effect, interstitial atoms drift towards the irradiated surface, but vacancies drift to the opposite direction - in the bulk of semiconductor. Since interstitials in Ge crystal are of n-type and vacancies are known to be of p-type, a n-p junction is formed. The mechanism is confirmed by the appearance of diode-like current-voltage characteristics after i-Ge irradiation crystal by laser radiation. The mechanism in Si is confirmed by conductivity type inversion and increased microhardness of Si crystal. The second stage of nanocone formation is laser heating up of top layer enriched by interstitial atoms with its further plastic deformation due to compressive stress caused by interstitials in the top layer and vacancies in the buried layer.

摘要

在这项工作中，我们研究了 Nd：YAG 激光辐射在元素半导体表面形成纳米锥的机制。我们之前对 SiGe 和 CdZnTe 固溶体的研究表明，纳米锥形成机制具有两个阶段。第一阶段的特征是形成异质结构，例如 SiGe 固溶体中的 Ge/Si 异质结构，第二阶段的特征是由于 Si 和 Ge 晶格的不匹配，通过压缩 Ge 层在 Si 上的机械塑性变形形成纳米锥。到目前为止，对于元素半导体的纳米锥形成机制还不清楚。因此，我们研究的主要目标是研究元素半导体中纳米锥形成的阶段。提出了一种新的通过激光辐射在元素半导体中形成 p-n 结作为纳米锥形成第一阶段的机制。我们通过以下方式解释这种效应：通过在温度梯度场中产生和重新分布本征点缺陷形成 p-n 结 - 热梯度效应，这是由强烈吸收的激光辐射引起的。根据热梯度效应，间隙原子向照射表面漂移，但空位向相反方向漂移 - 在半导体的体中。由于 Ge 晶体中的间隙原子为 n 型，而空位已知为 p 型，因此形成 n-p 结。激光辐照 i-Ge 晶体后出现类似二极管的电流-电压特性证实了该机制。在 Si 中的机制通过导电性类型反转和 Si 晶体的显微硬度增加得到证实。纳米锥形成的第二阶段是通过激光加热顶层来实现的，顶层富含间隙原子，由于顶层中的间隙原子和埋层中的空位产生的压缩应力，顶层进一步发生塑性变形。