Beckmann Yannick, Grundmann Annika, Daniel Leon, Abdelbaky Mohamed, McAleese Clifford, Wang Xiaochen, Conran Ben, Pasko Sergej, Krotkus Simonas, Heuken Michael, Kalisch Holger, Vescan Andrei, Mertin Wolfgang, Kümmell Tilmar, Bacher Gerd
Werkstoffe der Elektrotechnik and CENIDE, University of Duisburg-Essen, 47057 Duisburg, Germany.
Compound Semiconductor Technology, RWTH Aachen University, 52074 Aachen, Germany.
ACS Appl Mater Interfaces. 2022 Aug 3;14(30):35184-35193. doi: 10.1021/acsami.2c06047. Epub 2022 Jul 19.
A promising strategy toward ultrathin, sensitive photodetectors is the combination of a photoactive semiconducting transition-metal dichalcogenide (TMDC) monolayer like MoS with highly conductive graphene. Such devices often exhibit a complex and contradictory photoresponse as incident light can trigger both photoconductivity and photoinduced desorption of molecules from the surface. Here, we use metal-organic chemical vapor deposition (MOCVD) to directly grow MoS on top of graphene that is deposited on a sapphire wafer via chemical vapor deposition (CVD) for realizing graphene-MoS photodetectors. Two-color optical pump-electrical probe experiments allow for separation of light-induced carrier transfer across the graphene-MoS heterointerface from adsorbate-induced effects. We demonstrate that adsorbates strongly modify both magnitude and sign of the photoconductivity. This is attributed to a change of the graphene doping from p- to n-type in case adsorbates are being desorbed, while in either case, photogenerated electrons are transferred from MoS to graphene. This nondestructive probing method sheds light on the charge carrier transfer mechanisms and the role of adsorbates in two-dimensional (2D) heterostructure photodetectors.
制备超薄、灵敏光探测器的一种很有前景的策略是将像二硫化钼（MoS）这样的光活性半导体过渡金属二硫属化物单层与高导电性石墨烯相结合。这类器件常常表现出复杂且矛盾的光响应，因为入射光既能引发光导率变化，又能导致分子从表面发生光致解吸。在此，我们使用金属有机化学气相沉积（MOCVD）法，在通过化学气相沉积（CVD）法沉积在蓝宝石衬底上的石墨烯顶部直接生长二硫化钼（MoS），以实现石墨烯 - 二硫化钼（MoS）光探测器。双色光泵浦 - 电探针实验能够将光诱导的载流子穿过石墨烯 - 二硫化钼异质界面的转移与吸附质诱导的效应区分开来。我们证明，吸附质会强烈改变光导率的大小和符号。这归因于在吸附质解吸的情况下，石墨烯的掺杂从p型变为n型，而在任何一种情况下，光生电子都会从二硫化钼（MoS）转移到石墨烯上。这种非破坏性探测方法揭示了二维（2D）异质结构光探测器中的电荷载流子转移机制以及吸附质的作用。
