Correlation between Fermi-Level Hysteresis and Sulfur\nVacancy-Based Traps on MoS<sub>2</sub>

Two-dimensional\n(2D) transition metal dichalcogenides (TMDs) have\nemerged as promising candidates for memory cells and data storage\ndevices, thanks to their exceptional electrical properties and high\ndata storage capabilities enabled by their layered structures. Despite\nthe significant role of charge traps induced by defects in TMD-based\nmemory devices in contributing to hysteresis (Δ<i>V</i>) as a memory window, there remains a lack of research on how different\nenergy levels of these traps specifically affect Δ<i>V</i>. In this study, we report the simultaneous measurement of the spatially\ndistributed Δ<i>V</i> and energy-dependent trap density\n(<i>D</i><sub>t</sub>) in a MoS<sub>2</sub>/hBN structure\nby using Kelvin probe force microscopy. We observed a strong correlation\nof 0.61 between the Δ<i>V</i> and <i>D</i><sub>t</sub> in the trap states at 0.4–0.8 eV below the conduction\nband (<i>E</i><sub>C</sub>), which is attributed to sulfur\nvacancies (SVs) in MoS<sub>2</sub>. Additionally, a slight correlation\nof 0.3 between the Δ<i>V</i> and <i>D</i><sub>t</sub> in the trap states at approximately 0.4 eV below the <i>E</i><sub>C</sub> was observed, arising from the trap states\nvia the hybridization of individual SVs, aligning well with previous\nfindings. Furthermore, thiol molecule treatment on MoS<sub>2</sub> completely mitigates these correlations by healing the SVs. Our\ntechnique, capable of quantifying the energy levels of trap states\nand their impact on hysteresis, provides crucial insights into the\norigins of charge trap sources and their charge trapping mechanisms.\nThese insights are essential for the development of TMD-based memory\ndevices and data storage cells.