Synthesis and Raman spectroscopy of a layered SiS2 phase at high pressures.
Synthesis and Raman spectroscopy of a layered SiS2 phase at high pressures.
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DOI：
10.1063/1.5011333
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发表时间：
2018-01
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影响因子：
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通讯作者：
Yu Wang;Shu-qing Jiang;A. Goncharov;F. Gorelli;Xiao-Jia Chen;D. Plašienka;R. Martoňák;E. Tosatti;M. Santoro
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文献类型：
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作者：
Yu Wang;Shu-qing Jiang;A. Goncharov;F. Gorelli;Xiao-Jia Chen;D. Plašienka;R. Martoňák;E. Tosatti;M. Santoro
众所周知，二卤化物在常压和高压下表现出层状固体相，其中2D层的化学键合的分子式单元通过范德华力保持在一起。这些材料对固体科学和技术以及其他2D系统，如石墨烯和磷烯，都非常感兴趣。SiS2是一个原型模型系统，在这个整体中最有意义的是。最近，S从理论上预言了这种化合物中存在与硅处于八面体配位的高压相，并在实验上发现了它的存在。与SiO_6八面体三维网状结构的SiO_2中的辉石不同，SiS_2中具有八面体配位的相是二维层状的。非常重要的是，理论上预测，这种半导体材料在几十Gpa的压力下将呈现连续的带隙闭合，达到较差的金属状态。我们在金刚石压腔中合成了具有八面体配位的层状SiS_2，在7·5~9 Gpa的气压下，在1300~1700K的激光加热下，S和硅元素一起被激光加热。实际上，拉曼光谱在64.4 GPa时与这种材料的连续禁带闭合是相容的，在大约57 GPa时，要么是弱的金属性，要么是具有高密度缺陷诱导的带隙内能级的窄带隙半导体态。重要的是，我们的研究积累了层状二卤代化合物的基础知识。
Dichalcogenides are known to exhibit layered solid phases, at ambient and high pressures, where 2D layers of chemically bonded formula units are held together by van der Waals forces. These materials are of great interest for solid-state sciences and technology, along with other 2D systems such as graphene and phosphorene. SiS2 is an archetypal model system of the most fundamental interest within this ensemble. Recently, high pressure (GPa) phases with Si in octahedral coordination by S have been theoretically predicted and also experimentally found to occur in this compound. At variance with stishovite in SiO2, which is a 3D network of SiO6 octahedra, the phases with octahedral coordination in SiS2 are 2D layered. Very importantly, this type of semiconducting material was theoretically predicted to exhibit continuous bandgap closing with pressure to a poor metallic state at tens of GPa. We synthesized layered SiS2 with octahedral coordination in a diamond anvil cell at 7.5-9 GPa, by laser heating together elemental S and Si at 1300-1700 K. Indeed, Raman spectroscopy up to 64.4 GPa is compatible with continuous bandgap closing in this material with the onset of either weak metallicity or of a narrow bandgap semiconductor state with a large density of defect-induced, intra-gap energy levels, at about 57 GPa. Importantly, our investigation adds up to the fundamental knowledge of layered dichalcogenides.