准二维半导体材料的预测和应力调控的第一性原理研究

发布时间：2018-01-02 06:45

本文关键词：准二维半导体材料的预测和应力调控的第一性原理研究　出处：《清华大学》2016年博士论文　论文类型：学位论文

【摘要】：探索具有高性能输运特性和高柔韧性的新型准二维半导体材料是当前凝聚态物理领域的热点研究课题之一。基于第一性原理计算,本论文研究了拉伸应变对单层硒化锡输运性质的调控机制;预测了宽带隙的准二维半导体单层碘化铅和三碘化铋,并研究其对应变的响应;提出了一种特殊的调控石墨烯带隙的方法。首先,我们发现在零应变条件下,单层硒化锡是一种具有较高的电子迁移率的近直接带隙准二维半导体,其可承受的双轴拉伸应变极限约为12%。双轴拉伸应变能够有效调控单层硒化锡的带隙大小,同时可在2%的应变下实现间接带隙到直接带隙的转变并在较大的应变范围内(2%～8%)保持直接带隙的状态。零应变下,单层硒化锡中电子比空穴更易于移动,其迁移率高达1.5×104cm~2V~(-1)s~(-1)。随着双轴应变的增加,单层硒化锡的电子迁移率会逐渐下降,但在8%的应变之前都保持在600 cm~2V~(-1)s~(-1)之上。其次,我们预测了宽带隙半导体单层金属卤族化物(单层碘化铅和三碘化铋)的存在。单层碘化铅是一个带隙约为2.63 eV的间接带隙半导体。我们指出量子尺寸效应导致碘化铅从体的直接带隙转变到单层的间接带隙。双轴应变可以有效地调控该能隙大小,但无法实现从间接带隙到直接带隙的转变,这可以通过应变会均匀地改变铅和碘原子层之间的电场来理解。单层三碘化铋可以通过剥离方法获得。它也是一个间接带隙半导体,其带隙随层厚的增加而减小。在双轴拉伸应变下,单层、双层和三层的碘化铋带隙都呈下降趋势,这从侧面反映了碘化铋的层间耦合作用很弱。单层三碘化铋、碘化铅和石墨烯的复合结构都可以增强对可见光的吸收。最后,我们研究了在连续的石墨烯中形成的类似于zigzag-GNR的一维褶皱结构。提出了利用衬底作用和量子尺寸效应的联合效应在连续的石墨烯中打开能隙的方案。通过第一性原理计算,我们证实通过褶皱结构弯曲部分与衬底之间的强相互作用能够打开约0.7 eV的能隙。在不破坏完美石墨烯结构的情况下,实现金属-半导体-金属结,很好地解释了实验结果。
[Abstract]:It is one of the hot research topics in the field of condensed matter physics to explore new quasi-two-dimensional semiconductor materials with high performance transport characteristics and high flexibility. In this paper, the mechanism of the effect of tensile strain on the transport properties of monolayer tin selenide was studied. The quasi-two-dimensional semiconductor monolayer lead iodide and bismuth triiodide with wide band gap are predicted and their responses to strain are studied. A special method for controlling graphene band gap is proposed. Firstly, we find that the monolayer tin selenide is a near direct band gap quasi-two-dimensional semiconductor with high electron mobility under zero strain condition. The strain limit of biaxial tension is about 12. Biaxial tensile strain can effectively control the band gap of tin selenide monolayer. At the same time, the transition from indirect band gap to direct band gap can be realized at the strain of 2% and keep the state of direct band gap in a large strain range. It is easier to move electrons in monolayer tin selenide than holes, and its mobility is as high as 1.5 脳 10 ~ 4 cm ~ (2) C ~ (2) V ~ (-1) ~ (-1) ~ (-1) ~ 1 ~ (-1). The electron mobility of monolayer tin selenide decreases gradually, but before the strain of 8%, the electron mobility remains above 600cm ~ (2) V ~ (+) ~ (-1). We predicted the wide gap semiconductor monolayer metal halides (monolayer lead iodide and bismuth triiodide). Monolayer lead iodide is a band gap of about 2.63. We point out that the quantum size effect results in the transition of lead iodide from direct band gap to single layer indirect band gap. Biaxial strain can effectively regulate the size of the band gap. However, the transition from indirect band gap to direct band gap can not be realized. This can be understood by the fact that the strain changes the electric field between the lead and iodine atoms uniformly. The monolayer bismuth triiodide can be obtained by stripping. It is also an indirect band-gap semiconductor. The band gap decreases with the increase of layer thickness. Under biaxial tensile strain, the band-gap of bismuth iodide in single layer, double layer and three layer shows a downward trend, which reflects the weak interlaminar coupling of bismuth iodide. The composite structure of lead iodide and graphene can enhance the absorption of visible light. We have studied the one-dimensional fold structure similar to zigzag-GNR formed in continuous graphene. It is proposed that the energy gap is opened in continuous graphene by the combined effect of substrate action and quantum size effect. First principle calculation. It is shown that the energy gap of about 0.7 EV can be opened by the strong interaction between the bending part of the folded structure and the substrate, and the metal-semiconductor metal junction can be realized without destroying the perfect graphene structure. The experimental results are well explained.
【学位授予单位】：清华大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：O469

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