The transition metal dichalcogenides provide a rich field for the study of two-dimensional materials, with metals, semiconductors, superconductors and charge density wave materials being known. Members of this family are typically hexagonal, but those based on rhenium (ReSe₂ and ReS₂) and their ternary alloys are attracting attention due to their triclinic structure and their resulting, strong in-plane anisotropy. Here, Raman spectra of dilute ReSe_{2  -  x} S _x alloys containing low levels of sulfur (x ≤ 0.25) were obtained in order to investigate the distribution of substitutional sulfur atoms over the non-equivalent chalcogen sites of the ReSe₂ unit cell. Four different Raman bands arising from the local vibrational modes of sulfur atoms were observed, corresponding to these four sites. One local vibrational mode has a substantially in-plane displacement of the sulfur atom, two are partially out-of-plane and one is completely out-of-plane. The interpretation of the experimental data is based on calculations of the lattice dynamics and non-resonant Raman tensors of a model alloy via density functional theory. For comparison, polarization-dependent Raman spectra of pure ReS₂ are also presented; a dramatic increase in the Raman cross-section is found for the out-of-plane modes when the excitation polarization is normal to the layers and the light propagates in the layer plane. A similar increase in cross-section is found experimentally for the local vibrational modes of sulfur in dilute ReSe_2 -x S _x alloys and is predicted for dilute sulfur-containing alloys based on MoSe₂. The analogous local vibrational modes of substitutional oxygen impurities in ReSe₂ were also investigated computationally.

过渡金属二卤化物为二维材料的研究提供了广阔的领域，其中金属，半导体，超导体和电荷密度波材料是众所周知的。该族的成员通常是六角形的，但是基于rh的元素（ReSe ₂和ReS ₂）及其三元合金由于其三斜结构和由此产生的强的面内各向异性而引起了人们的关注。在此，稀的拉曼光谱RESE _{2  -  X}小号_X合金含有硫（低水平X  ≤0.25）为了调查取代的硫原子上的RESE非等效硫属部位的分布，获得₂ 晶胞。观察到由硫原子的局部振动模式引起的四个不同的拉曼谱带，对应于这四个位置。一种局部振动模式具有硫原子的基本上在平面内的位移，两种局部地处于平面外，而一种完全在平面外。对实验数据的解释是基于通过密度泛函理论计算模型合金的晶格动力学和非共振拉曼张量。为了进行比较，纯ReS _2的偏振相关拉曼光谱也提出了；当激发偏振垂直于层并且光在层平面中传播时，对于平面外模式，发现拉曼横截面显着增加。通过实验发现，在稀ReSe _{2- x} S _x合金中，硫的局部振动模态具有类似的横截面增加，并预测了基于MoSe _2的稀含硫合金的横截面。还对ReSe ₂中取代氧杂质的类似局部振动模式进行了研究。