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首页> 外文期刊>Physical review >Theoretical investigation of silicon nanowires: Methodology, geometry, surface modification, and electrical conductivity using a multiscale approach
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Theoretical investigation of silicon nanowires: Methodology, geometry, surface modification, and electrical conductivity using a multiscale approach

机译：硅纳米线的理论研究：方法，几何，表面改性和使用多尺度方法的电导率

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摘要

The structural and electronic properties of hydrogenated silicon nanowires (SiNWs) oriented in <100>, <110>, <111>, and <112> directions are investigated systematically using a multiscale approach: geometry optimization is done by a semiempirical method and electronic band structure is calculated by density-functional theory with Gaussian basis set. The calculated band gaps agree very well with the available experimental data. We propose that the multiscale approach is an accurate and effective way for calculating the structural and electronic properties of SiNWs with diameter up to 3 nm. Besides, we found that surface modification of the SiNWs using the hydroxyl and fluoro groups can strongly reduce the band gap by as much as 1 eV, and more interestingly, alter the gap nature. On the contrary, the (110) SiNWs exhibiting different patterns at the cross section do not show significant difference in their band gaps ( < 0.09 eV), indicating that the electronic structures of SiNWs are much more sensitive to surface modification than the change of cross section. Moreover, SiNWs of different orientations exhibit different degrees of band gap reduction upon surface modification, in which the <110> SiNW demonstrates the highest sensitivity. The result indicates that SiNWs oriented in <110> direction are the better candidate for sensor application. On the contrary, the <111> SiNW is found to be very tight to structural change with diameter and the most reluctant to surface modification, showing that it is structurally stable and rather inert. In addition, from the I-V curves of the SiNWs with surfaces modified with hydroxyl groups, which are calculated by the nonequilibrium Green's function theory, we found that the electrical conductivity of the SiNWs is highly chemical sensitive. Besides, the phenomenon of negative differential resistance is observed in the I-V curves.
机译：使用多尺度方法系统地研究了沿<100>，<110>，<111>和<112>方向取向的氢化硅纳米线（SiNW）的结构和电子特性：通过半经验方法和电子能带完成了几何优化通过密度泛函理论和高斯基集计算结构。计算的带隙与可用的实验数据非常吻合。我们建议，多尺度方法是一种计算直径最大为3 nm的SiNW的结构和电子特性的准确有效的方法。此外，我们发现使用羟基和氟基团对SiNWs进行表面改性可以将带隙降低多达1 eV，并且更有趣的是，改变了间隙性质。相反，在横截面上表现出不同图案的（110）SiNW的带隙（<0.09 eV）没有显着差异，这表明SiNW的电子结构对表面改性的敏感性比交叉变化要大得多。部分。此外，不同方向的SiNW在表面改性时表现出不同程度的带隙减小，其中<110> SiNW表现出最高的灵敏度。结果表明，以<110>方向取向的SiNW是传感器应用的更好候选者。相反，发现<111> SiNW对于随直径变化的结构非常紧密，并且最不愿意进行表面改性，表明它在结构上是稳定的，并且是惰性的。此外，根据非平衡格林函数理论计算得到的，表面被羟基改性的氮化硅的I-V曲线，我们发现氮化硅的电导率具有很高的化学敏感性。此外，在IV曲线中观察到负的差动电阻现象。

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