Yoon Aram, Kim Jung Hwa, Yoon Jongchan, Lee Yeongdong, Lee Zonghoon
Center for Multidimensional Carbon Materials, Institute for Basic Science (IBS), Ulsan 44919, Republic of Korea.
School of Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea.
ACS Appl Mater Interfaces. 2020 May 13;12(19):22029-22036. doi: 10.1021/acsami.0c03032. Epub 2020 Apr 28.
The electronic, catalytic, and optical properties of transition metal dichalcogenides (TMDs) are significantly affected by oxidation, and using oxidation to tune the properties of TMDs has been actively explored. In particular, because transition metal oxides (TMOs) are promising hole injection layers, a TMD-TMO heterostructure can be potentially applied as a p-type semiconductor. However, the oxidation of TMDs has not been clearly elucidated because of the structural instability and the extremely small quantity of oxides formed. Here, we reveal the phases and morphologies of oxides formed on two-dimensional molybdenum disulfide (MoS) using transmission electron microscopy analysis. We find that MoS starts to oxidize around 400 °C to form orthorhombic-phase molybdenum trioxide (α-MoO) nanosheets. The α-MoO nanosheets so formed are stacked layer-by-layer on the underlying MoS via van der Waals interaction and the nanosheets are aligned epitaxially with six possible orientations. Furthermore, the band gap of MoS is increased from 1.27 to 3.0 eV through oxidation. Our study can be extended to most TMDs to form TMO-TMD heterostructures, which are potentially interesting as p-type transistors, gas sensors, or photocatalysts.
过渡金属二硫属化物（TMDs）的电子、催化和光学性质会受到氧化的显著影响，利用氧化来调控TMDs的性质已得到积极探索。特别是，由于过渡金属氧化物（TMOs）是很有前景的空穴注入层，TMD-TMO异质结构有可能被用作p型半导体。然而，由于结构不稳定性以及形成的氧化物数量极少，TMDs的氧化情况尚未得到明确阐释。在此，我们利用透射电子显微镜分析揭示了二维二硫化钼（MoS）上形成的氧化物的相和形貌。我们发现MoS在约400℃开始氧化，形成正交相三氧化钼（α-MoO）纳米片。如此形成的α-MoO纳米片通过范德华相互作用逐层堆叠在下层的MoS上，且纳米片以六种可能的取向外延排列。此外，MoS的带隙通过氧化从1.27 eV增加到3.0 eV。我们的研究可以扩展到大多数TMDs，以形成TMO-TMD异质结构，这作为p型晶体管、气体传感器或光催化剂可能具有吸引力。
