Grundmann Annika, Beckmann Yannick, Ghiami Amir, Bui Minh, Kardynal Beata, Patterer Lena, Schneider Jochen, Kümmell Tilmar, Bacher Gerd, Heuken Michael, Kalisch Holger, Vescan Andrei
Compound Semiconductor Technology, RWTH Aachen University, D-52074 Aachen, Germany.
Werkstoffe der Elektrotechnik and CENIDE, University of Duisburg-Essen, D-47057 Duisburg, Germany.
Nanotechnology. 2023 Mar 1;34(20). doi: 10.1088/1361-6528/acb947.
Structural defects in transition metal dichalcogenide (TMDC) monolayers (ML) play a significant role in determining their (opto)electronic properties, triggering numerous efforts to control defect densities during material growth or by post-growth treatments. Various types of TMDC have been successfully deposited by MOCVD (metal-organic chemical vapor deposition), which is a wafer-scale deposition technique with excellent uniformity and controllability. However, so far there are no findings on the extent to which the incorporation of defects can be controlled by growth parameters during MOCVD processes of TMDC. In this work, we investigate the effect of growth temperature and precursor ratio during MOCVD of tungsten diselenide (WSe) on the growth of ML domains and their impact on the density of defects. The aim is to find parameter windows that enable the deposition of WSeML with high crystal quality, i.e. a low density of defects. Our findings confirm that the growth temperature has a large influence on the crystal quality of TMDC, significantly stronger than found for the W to Se precursor ratio. Raising the growth temperatures in the range of 688 °C to 791 °C leads to an increase of the number of defects, dominating photoluminescence (PL) at low temperatures (5.6 K). In contrast, an increase of the molar precursor ratio (DiPSe/WCO) from 1000 up to 100 000 leads to less defect-related PL at low temperatures.
过渡金属二硫族化合物（TMDC）单层（ML）中的结构缺陷在决定其（光）电子特性方面起着重要作用，引发了众多在材料生长过程中或通过生长后处理来控制缺陷密度的努力。各种类型的TMDC已通过金属有机化学气相沉积（MOCVD）成功沉积，这是一种具有出色均匀性和可控性的晶圆级沉积技术。然而，到目前为止，关于在TMDC的MOCVD过程中生长参数能在多大程度上控制缺陷掺入尚无相关发现。在这项工作中，我们研究了二硒化钨（WSe）的MOCVD过程中生长温度和前驱体比例对ML畴生长及其对缺陷密度的影响。目的是找到能够实现高质量晶体（即低密度缺陷）的WSeML沉积的参数窗口。我们的研究结果证实，生长温度对TMDC的晶体质量有很大影响，比钨与硒前驱体比例的影响要显著得多。将生长温度提高到688°C至791°C会导致缺陷数量增加，在低温（5.6 K）下主导光致发光（PL）。相比之下，将前驱体摩尔比（DiPSe/WCO）从1000提高到100000会导致低温下与缺陷相关的PL减少。
