Hynek David J, Singhania Raivat M, Xu Shiyu, Davis Benjamin, Wang Leizhi, Yarali Milad, Pondick Joshua V, Woods John M, Strandwitz Nicholas C, Cha Judy J
Energy Sciences Institute, Department of Mechanical Engineering and Materials Science, Yale University, West Haven, Connecticut 06516, United States.
Department of Materials Science and Engineering, Lehigh University, Bethlehem, Pennsylvania 18015, United States.
ACS Nano. 2021 Jan 26;15(1):410-418. doi: 10.1021/acsnano.0c08069. Epub 2020 Nov 19.
Owing to the small energy differences between its polymorphs, MoTe can access a full spectrum of electronic states from the 2H semiconducting state to the 1T' semimetallic state and from the T Weyl semimetallic state to the superconducting state in the 1T' and T phase at low temperature. Thus, it is a model system for phase transformation studies as well as quantum phenomena such as the quantum spin Hall effect and topological superconductivity. Careful studies of MoTe and its potential applications require large-area MoTe thin films with high crystallinity and thickness control. Here, we present cm-scale synthesis of 2H-MoTe thin films with layer control and large grains that span several microns. Layer control is achieved by controlling the initial thickness of the precursor MoO thin films, which are deposited on sapphire substrates by atomic layer deposition and subsequently tellurized. Despite the van der Waals epitaxy, the precursor-substrate interface is found to critically determine the uniformity in thickness and grain size of the resulting MoTe films: MoTe grown on sapphire show uniform films while MoTe grown on amorphous SiO substrates form islands. This synthesis strategy decouples the layer control from the variabilities of growth conditions for robust growth results and is applicable to growing other transition-metal dichalcogenides with layer control.
由于其多晶型之间的能量差异较小，碲化钼（MoTe）在低温下能够在1T'和T相中从2H半导体态到1T'半金属态，以及从T外尔半金属态到超导态，访问全谱电子态。因此，它是用于相变研究以及量子现象（如量子自旋霍尔效应和拓扑超导）的模型系统。对MoTe及其潜在应用的仔细研究需要具有高结晶度和厚度可控的大面积MoTe薄膜。在此，我们展示了具有层控制和跨越几微米大晶粒的厘米级2H-MoTe薄膜的合成。通过控制前驱体MoO薄膜的初始厚度来实现层控制，该薄膜通过原子层沉积法沉积在蓝宝石衬底上，随后进行碲化处理。尽管存在范德华外延，但发现前驱体 - 衬底界面对于所得MoTe薄膜的厚度和晶粒尺寸均匀性起着关键作用：在蓝宝石上生长的MoTe呈现均匀的薄膜，而在非晶SiO衬底上生长的MoTe形成岛状。这种合成策略将层控制与生长条件的变化解耦，以获得稳健的生长结果，并且适用于生长其他具有层控制的过渡金属二硫属化物。
