Single-Layer Janus-Type Platinum Dichalcogenides and Their Heterostructures
Single-Layer Janus-Type Platinum Dichalcogenides and Their Heterostructures
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DOI：
10.1021/acs.jpcc.8b11837
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发表时间：
2019-02-21
影响因子：
3.7
通讯作者：
Sahin, H.
中科院分区：
文献类型：
--
作者：
Kahraman, Z.;Kandemir, A.;Sahin, H.
超薄二维双硫化物型铂晶体由两个不同的原子在相对的表面形成，通过执行最先进的密度泛函理论计算进行了研究。首先，单层PtX2结构（其中X = S， Se或Te）结晶成动态稳定的it相，是间接带隙半导体。研究还发现，在PtX2的所有结构中，通过用更小的硫原子取代表面原子，有利于取代硫掺杂，从而形成新的单层janus型二硫族铂（XPtY，其中X和Y分别代表S、Se和Te）。虽然所有的Janus结构都是间接的带隙半导体，但它们的拉曼光谱显示出源于面外对称破碎的独特特征。此外，Janus晶体的构造显著提高了PtX2晶体在平面内和平面外方向的压电常数。此外，二元和三元（Janus）铂二硫族化合物垂直堆叠的范德华异质结构分别形成了i型、ii型和iii型的双层异质结，提供了广泛的电子特征。我们的研究结果表明，janus型超薄二硫化铂晶体是一种非常有前途的光电子器件材料。
Ultrathin two-dimensional Janus-type platinum dichalcogenide crystals formed by two different atoms at opposite surfaces are investigated by performing state-of-the-art density functional theory calculations. First, it is shown that single-layer PtX2 structures (where X = S, Se, or Te) crystallize into the dynamically stable IT phase and are indirect band gap semiconductors. It is also found that the substitutional chalcogen doping in all PtX2 structures is favorable via replacement of surface atoms with a smaller chalcogen atom, and such a process leads to the formation of Janus-type platinum dichalcogenides (XPtY, where X and Y stand for S, Se, or Te) which are novel single-layer crystals. While all Janus structures are indirect band gap semiconductors as their binary analogues, their Raman spectra show distinctive features that stem from the broken out-of-plane symmetry. In addition, it is revealed that the construction of Janus crystals enhances the piezoelectric constants of PtX2 crystals significantly both in the in plane and in the out-of-plane directions. Moreover, it is shown that vertically stacked van der Waals heterostructures of binary and ternary (Janus) platinum dichalcogenides offer a wide range of electronic features by forming bilayer heterojunctions of type-I, type-II, and type-III, respectively. Our findings reveal that Janus-type ultrathin platinum dichalcogenide crystals are quite promising materials for optoelectronic device applications.