Localized States’ Role in MoS2 Few-Layer Device: A Study by Schottky Capacitance Spectroscopy and Thermally Stimulated Current

Abstract

This paper reports on the Chemical Vapor Deposition synthesis of few-layer molybdenum disulfide (MoS2) films, with their two-dimensional nature confirmed by Raman and photoluminescence spectroscopies. Raman analysis revealed a frequency separation of 22.2 cm–1 between the E2g1 and A1g modes, indicating a structure with fewer than 4 atomic layers. To investigate interface and transport properties, planar diode-type devices were fabricated using Au and In/Au contacts. Temperature-dependent electrical characterizations demonstrated that charge transport is governed by a 2D Variable Range Hopping mechanism, highlighting the influence of localized states. Through Thermally Stimulated Current (TSC) spectroscopy, we identified trap levels with an activation energy of approximately 120 meV, attributed to sulfur vacancies. Additionally, Schottky Capacitance Spectroscopy (SCS) revealed a nearly uniform distribution of interface states with a density on the order of 1011 cm–2 eV–1. The high consistency between TSC and SCS results confirms that localized states dominate both the metal–semiconductor contact behavior and the overall charge transport in few-layer MoS2 devices.