Resistive switching behavior and bandgap analysis of two-dimensional HfS2 via density functional theory simulations

Abstract

Silicon-based memory and semiconductor technologies have recently approached their physical and spatial limits, making further advancements challenging. One promising solution to overcome this challenge is the exploration of transition metal dichalcogenides (TMDCs) for resistive random-access memory (RRAM) based on non-volatile memory and conductive filament mechanisms. Among the various TMDC materials, HfS2 has demonstrated significant potential for high-performance electronic devices. In particular, HfS2 has been used in resistive switching and field-effect transistor (FET) devices owing to its exceptionally high electron mobility, ON/ OFF ratio, and appropriate bandgap at room temperature. This study performed simulations based on density functional theory (DFT) to calculate the S vacancy formation energy, bandgap, and density of states required for using two-dimensional (2D) HfS2 as a resistive switching device. During the transition to the SET state, a conductive filament was assumed to form owing to vacancies created by removing sulfur atoms. Conversely, during the transition to the RESET state, these vacancies are refilled, restoring the atomic structure. When seven sulfur atoms were removed, the bandgap became zero. When the sulfur atoms were restored, the atomic structure and bandgap reverted to their initial states. This indicates a SET/RESET process, highlighting the potential of HfS2 for application in resistive switching devices. This study provides insights into developing energy-efficient, scalable, and high-performance memory devices critical for future computing needs.