Intertwined bulk photocarrier and interfacial barrier dynamics in van der Waals point-contact Schottky junctions

Abstract

Schottky junctions based on transition-metal dichalcogenides underpin next-generation optoelectronic devices, yet the nanoscale carrier dynamics that ultimately govern their performance remain largely inaccessible. Here, we employ optical pump-probe time-resolved atomic force microscopy (OPP-TR-AFM) to investigate the spatiotemporal response of a WSe${}_2$/PtIr van der Waals Schottky junction. Under backside illumination, photocarriers generated in bulk WSe${}_2$ produce a local junction response through coupled bulk carrier transport and interfacial barrier modulation. We show that the time-resolved current is consistently explained by the competition between long-lived hole diffusion governed by the occupancy of bulk trap states and thermionic emission current modulated by the surface photovoltage. This mechanism is supported by transient absorption spectroscopy, light-modulated current-voltage measurements, and numerical simulations. Furthermore, spatial mapping reveals pronounced nanoscale variations in the coupled dynamics of carrier transport and interfacial barrier modulation. These results demonstrate that OPP-TR-AFM provides a new framework for resolving the coupled behavior of bulk carriers and interfacial barrier dynamics in van der Waals Schottky junctions with simultaneous spatial and temporal resolution, establishing it as a powerful approach for investigating the microscopic processes that play a crucial role in the development of next-generation optoelectronic devices.

arXiv comment37 pages, 5 figures, Supporting Information included. Accepted for publication in npj 2D Materials and Applications