Intrinsically Substitutional Carbon Doping in CVD-Grown Monolayer MoS2 and the Band Structure Modulation
Intrinsically Substitutional Carbon Doping in CVD-Grown Monolayer MoS2 and the Band Structure Modulation
复制标题
CVD 生长的单层 MoS2 中的本征替代碳掺杂和能带结构调制
DOI：
10.1021/acsaelm.0c00076
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发表时间：
2020-04-28
影响因子：
4.7
通讯作者：
Xu, Mingsheng
中科院分区：
文献类型：
--
作者：
Liang, Tao;Habib, Mohammad Rezwan;Xu, Mingsheng
多相原子掺杂已被证明是调整半导体物理和化学性质的有效途径，以技术成熟的体硅中的硼和磷掺杂为代表。在二维过渡金属二卤化物半导体中，由于二维材料的超薄性质，与间隙位掺杂相比，代位掺杂占主导地位。然而，无意的掺杂也会模糊结构-性质的关系，导致偏离理想的光学/电学性能。通过对中间产物和最终产物的深入分析，发现在常规的化学气相沉积(CVD)合成过程中，取代碳掺杂到了单层二硫化钼(MoS2)晶格中。碳来自较低纯度的钼前驱体，使用高纯度钼前驱体可以完全消除碳。掺碳单层MoS_2呈现由Mo-d、S-p和C-p轨道杂化引起的中间能隙状态，并随着掺杂浓度的增加而逐渐减小。结果发现，样品的光致发光强度受到抑制，发光位置发生红移。这一发现对于理解CVD生长2D半导体中非故意的碳掺杂过程是基础的，并确定了CVD衍生样品中不一致的发光性能的来源。
Heterogeneous atom doping has been proven as an efficient route to tune the physical and chemical properties of semiconductors, represented by the technically mature boron and phosphorus doping in bulk silicon. In the two-dimensional (2D) transitional-metal dichalcogenides semiconductors, substitutional doping dominates compared with the interstitial sites doping due to the ultrathin nature of 2D materials. However, unintentional doping can also obscure the structure-property relationship and cause the deviations from the ideally optical/electrical performances. Here, substitutional carbon doping into the monolayer molybdenum disulfide (MoS2) lattice during the normal chemical vapor deposition (CVD) synthesis process is discovered through a thorough analysis of the intermediate and final reaction products. The carbon originates from the relatively low-purity molybdenum precursor, which can be completely eliminated when a high-purity molybdenum precursor is utilized. The carbon-doped monolayer MoS2 exhibits mid-gap states brought by the Mo-d, S-p, and C-p orbital hybridization and gradually reduced band gaps as the doping concentration increases. As a result, the suppressed photoluminescence (PL) intensity and red shift PL position are observed. The finding is fundamental for understanding the unintentional carbon doping process in CVD growth of 2D semiconductors and identifies a source for the inconsistent PL performances in the CVD-derived samples.