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arXiv 1609.04381cond-mat.mtrl-scicond-mat.mes-hallcond-mat.other
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SnS2和SnSe2新型二维材料的层相关性质

Layer-dependent properties of SnS2 and SnSe2 novel two-dimensional materials

Joseph M. Gonzalez, Ivan I. Oleynik

摘要:

采用第一性原理密度泛函理论研究了SnS 2和SnSe 2的结构、电子和振动性质。面内晶格常数,层间距和结合能被发现是层无关的。体SnS 2和SnSe 2都是间接带隙半导体,Eg分别为2.18 eV和1.07 eV。少层和单层2D系统也具有间接带隙,对于SnS 2和SnSe 2的单层,其增加到2.41 eV和1.69 eV。二维激子的有效质量理论考虑了各向异性、非局域二维屏蔽和层依赖的三维屏蔽的综合影响,预测了强激子效应。单层样品中的间接激子的结合能,Ex~ 0.9eV,在块状SnS 2中基本上降低到Ex = 0.14eV,在块状SnSe 2中基本上降低到Ex = 0.09eV。层相关的拉曼光谱显示的拉曼活性A1 g模式的强度的强烈减少后,减少到单层的层数,由一个因素的7的情况下的SnS 2和一个因素的20的情况下的SnSe 2,可以用来确定在一个2D样品中的层数。

英文摘要:

The layer dependent structural, electronic and vibrational properties of SnS2 and SnSe2 are investigated using first-principles density functional theory (DFT). The in-plane lattice constants, interlayer distances and binding energies are found to be layer-independent. Bulk SnS2 and SnSe2 are both indirect band gap semiconductors with Eg = 2.18 eV and 1.07 eV, respectively. Few-layer and monolayer 2D systems also possess an indirect band gap, which is increased to 2.41 eV and 1.69 eV for single layers of SnS2 and SnSe2. The effective mass theory of 2D excitons, which takes into account the combined effect of the anisotropy, non-local 2D screening and layer-dependent 3D screening, predicts strong excitonic effects. The binding energy of indirect excitons in monolayer samples, Ex~0.9 eV, is substantially reduced to Ex = 0.14 eV in bulk SnS2 and Ex = 0.09 eV in bulk SnSe2. The layer-dependent Raman spectra display a strong decrease of intensities of the Raman active A1g mode upon decreasing the number of layers down to a monolayer, by a factor of 7 in the case of SnS2 and a factor of 20 in the case of SnSe2 which can be used to identify number of layers in a 2D sample.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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