Multimodal Nanoscopic Study of Atomic Diffusion and Related Localized Optoelectronic Response of WS2/MoS2 Lateral Heterojunctions

Jiaqi Shao; Fei Chen; Weitao Su; Yijie Zeng; Hong-Wei Lu

doi:10.1021/acsami.1c03061

Multimodal Nanoscopic Study of Atomic Diffusion and Related Localized Optoelectronic Response of WS₂/MoS₂ Lateral Heterojunctions

ACS Appl Mater Interfaces. 2021 May 5;13(17):20361-20370. doi: 10.1021/acsami.1c03061. Epub 2021 Apr 23.

Authors

Jiaqi Shao¹, Fei Chen¹, Weitao Su^{1

2}, Yijie Zeng², Hong-Wei Lu²

Affiliations

¹ College of Materials and Environmental Engineering, Hangzhou Dianzi University, 310018 Hangzhou, P. R. China.
² School of Sciences, Hangzhou Dianzi University, 310018 Hangzhou, P. R. China.

PMID: 33890458
DOI: 10.1021/acsami.1c03061

Abstract

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) WS₂/MoS₂ 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^-12 and ∼1 × 10^-12 cm²/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.

Keywords: atomic diffusion; bilayer WS2/MoS2 heterojunction; localized optoelectronic property; tip enhanced Raman spectroscopy; tip enhanced photoluminescence.