Shao Jiaqi, Chen Fei, Su Weitao, Zeng Yijie, Lu Hong-Wei
College of Materials and Environmental Engineering, Hangzhou Dianzi University, 310018 Hangzhou, P. R. China.
School of Sciences, Hangzhou Dianzi University, 310018 Hangzhou, P. R. China.
ACS Appl Mater Interfaces. 2021 May 5;13(17):20361-20370. doi: 10.1021/acsami.1c03061. Epub 2021 Apr 23.
The atomic diffusion in transition metal dichalcogenides (TMDs) van der Waals heterojunctions (HJs) strongly modifies their optoelectronic properties in the nanoscale. However, probing such localized properties challenges the spatial resolution and the sensitivity of a variety of analytic tools. Herein, a multimodal nanoscopy (based on tip enhanced Raman spectroscopy (TERS) and photoluminescence (TEPL)) combined with the Kelvin probe force microscopy (KPFM) method was used to probe such nanoscale localized optoelectronic properties induced by atomic diffusion. Chemical vapor deposition (CVD)-grown lateral bilayer (2L) WS/MoS HJs were imaged with a spatial resolution better than 40 nm via TERS and TEPL mapping by using intrinsic Raman and photoluminescence (PL) peaks. The contact potential difference (CPD), capacitance, and PL variation in a nanoscale vicinity of the HJ interface can be correlated to the local stoichiometry variation determined by TERS. The diffusion coefficients of W and Mo were obtained to be ∼0.5 × 10 and ∼1 × 10 cm/s, respectively, by using Fick's second law. The obtained results would be useful to further understand the localized optoelectronic response of the TMDs HJs.
过渡金属二硫属化物（TMDs）范德华异质结（HJs）中的原子扩散在纳米尺度上强烈改变其光电特性。然而，探测此类局部特性对各种分析工具的空间分辨率和灵敏度提出了挑战。在此，采用了一种结合开尔文探针力显微镜（KPFM）方法的多模态纳米显微镜（基于针尖增强拉曼光谱（TERS）和光致发光（TEPL））来探测由原子扩散引起的此类纳米尺度局部光电特性。通过使用本征拉曼和光致发光（PL）峰，利用TERS和TEPL映射对化学气相沉积（CVD）生长的横向双层（2L）WS/MoS HJs进行了空间分辨率优于40 nm的成像。HJ界面纳米尺度附近的接触电势差（CPD）、电容和PL变化可以与由TERS确定的局部化学计量变化相关联。通过使用菲克第二定律，得到W和Mo的扩散系数分别约为0.5×10和1×10 cm²/s。所得结果将有助于进一步理解TMDs HJs的局部光电响应。
