Abstract

By plane-wave pseudopotential techniques we simulated structural and electronic properties of novel two-dimensional (2D) materials composed of Si and Ge randomly placed at the lattice sites of a honeycomb structure: 2D-Si_1−xGe_x, and 2D-(H@Si)_1−x(Ge@H)_x, the corresponding H-passivated alloy. We investigated the formation of a random network of Si and Ge in 2D-honeycomb structure and proved the thermal stability of H-passivated SiGe alloy by computing the formation energy of these 2D-compounds. The 2D-Si_1−xGe_x random alloy is a semi-metal and presents at the Fermi energy a density of states resembling the one produced by the Dirac’s cone of silicene and germanene, suggesting the possibility to induce, in 2D-Si_1−xGe_x Dirac’s cone, a population of high velocity carriers that behaves like massless Dirac fermions. The 2D-(H@Si)_1−x(Ge@H)_x random alloy is a semiconductor and presents a tunable direct bandgap that doubles by decreasing the concentration from x = 1 to x = 0.25, making this 2D-alloy suitable for opto-electronic applications. The lattice parameter of both 2D-alloys increases linearly with Ge concentration, thus providing a microscopic mechanism to engineer the lattice parameter and/or the electronic properties of 2D-heterostructures based on these 2D-materials. The study of elastic properties of 2D-@Si_1−xGe_x and 2D-(H@Si)_1−x(Ge@H)_x as a function of x for possible use in flexible electronics and the investigation of magnetic properties of partially H-passivated 2D-(H@Si)_1−xGe_x random alloy for concentration close to x = 0.5 for spintronic applications complete the work.

Graphical abstract

中文翻译：

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调整二维Si和Ge基无规合金的结构和电子性能：从头算研究

摘要

通过平面波伪势技术，我们模拟了由Si和Ge组成的新型二维（2D）材料的结构和电子特性，这些材料随机放置在蜂窝结构的晶格位置：2D-Si ₁ - _x Ge _x和2D-（ H @ Si）_{1- x}（Ge @ H）_x，相应的H钝化合金。我们研究了二维蜂窝结构中Si和Ge随机网络的形成，并通过计算这些二维化合物的形成能证明了H钝化SiGe合金的热稳定性。2D-Si ₁ - _x Ge _x无规合金是一种半金属，在费米能量处呈现出类似于狄拉克硅和锗锥所产生的态密度，这表明有可能在2D-Si _{1− x} Ge _x狄拉克锥中诱发一个种群。表现得像无质量狄拉克费米子的高速载子。2D-（H @ Si）_{1- x}（Ge @ H）_x无规合金是一种半导体，具有可调谐的直接带隙，通过将浓度从x = 1降低到x可以使能带隙增加一倍= 0.25，使这种2D合金适用于光电应用。两种2D合金的晶格参数均随Ge浓度线性增加，因此提供了一种微观机制，可基于这些2D材料来设计2D异质结构的晶格参数和/或电子性质。2D-的弹性性质的研究@硅_{1- X}的Ge _X和2D-（H @ Si）的_{1- X}（葛@ 1H）_X的函数关系X为在柔性电子可能使用和磁特性的调查部分H钝化的2D-（H @ Si）的_{1- X}葛_X随机对于浓度接近合金X = 0.5（对于自旋电子应用）完成工作。

图形概要