GaN基底上单层WS₂调控生长及其光学性质研究

Controlled Growth of Monolayer WS₂ on GaN Substrate and Its Optical Properties

摘要: 本文采用化学气相沉积法在GaN上调控生长了单层WS₂，并研究了基底耦合效应对其光学性质的影响。研究结果显示，生长温度为850℃，可以生长出质量较好的单层三角形WS₂；当温度大于900℃时，GaN基底表面开始发生分解，不利于材料生长。通过载气H2流量调节，可在基底上生长出满覆盖的WS₂。GaN基底上生长的三角形WS₂呈现良好的60˚旋转对称性，通过GaN纳米柱上WS₂的生长与第一性原理模拟计算，推测出了WS₂/GaN样品的稳定结构。通过拉曼表征发现，GaN基底会对WS₂产生一定的张应力作用，使E_2g¹拉曼峰和激子峰出现红移，并且由于WS₂与GaN基底形成Ⅱ型异质结能带结构，WS₂/GaN样品出现发光淬灭现象。本文为开发新型二维光电子器件提供了一定的实验依据。

Abstract: The growth of monolayer WS₂ on GaN substrate by chemical vapor deposition method is explored, and the effect of the substrate on its optical properties is investigated. The results show that the monolayer triangular WS₂ with good quality can be grown under the growth temperature of 850˚C. When the growth temperature is greater than 900˚C, slight decomposition of the substrate surface occurs, which is not conducive to the growth. In addition, by controlling the flow rate of H2 carrier gas properly, WS₂ with full coverage can be grown on the substrate. The as-grown triangular WS₂ on GaN substrate shows 60˚ rotation symmetry. The most stable structure of WS₂/GaN is predicted by combining the growth of WS₂ on GaN nanorod and the first-principles calculations. It is found by Raman characterization that GaN substrate would exert certain tensile stress on WS₂, resulting in the redshift of the Raman peak E_2g¹ and the photoluminescence peak. Photoluminescence quench-ing emerges in WS₂/GaN sample, which is attributed to the formation of type-II heterojunction band structure between WS₂ and GaN substrate. This work provides a reference for the development of new 2-dimensional optoelectronic devices.