Electrical Stressing Induced Monolayer Vacancy Island Growth on TiSe₂

Abstract

To ensure practical applications of atomically thin transition metal dichalcogenides, it is essential to characterize their structural stability under external stimuli such as electric fields and currents. Using vacancy monolayer islands on TiSe surfaces as a model system, we have observed nonlinear area evolution and growth from triangular to hexagonal driven by scanning tunneling microscopy (STM) subjected electrical stressing. The observed growth dynamics represent a 2D departure from the linear area growth law expected for bulk vacancy clustering. Our simulations of monolayer island evolution using phase-field modeling and first-principles calculations are in good agreement with our experimental observations, and point toward preferential edge atom dissociation under STM scanning driving the observed nonlinear area growth. We further quantified a parabolic growth rate dependence with respect to the tunneling current magnitude. The results could be potentially important for device reliability in systems containing ultrathin transition metal dichalcogenides and related 2D materials subject to electrical stressing.

Visualization of point defects in ultrathin layered 1T-PtSe 2

“…A highresolution STM topographic image of a defect-free 1T-PtSe 2 surface is shown in figure 1(c). Similar to previous STM study on monolayer PtSe 2 grown though selenization of a Pt(1 1 1) substrate and other transition-metal diselenides [2,59], the hexagonal protrusions in figure 1(c) represent the topmost Se atoms. From the arrangement of the surface Se atoms, the in-plane lattice constant of 1T-PtSe 2 is determined to be 0.375 ± 0.003 nm, which is consistent with previous theoretical and experimental results [2,17,60].…”

“…Similar to previous STM study on monolayer PtSe2 grown though selenization of a Pt(111) substrate and other transitionmetal diselenides, the hexagonal protrusions in FIG. 1c represent the topmost Se atoms [2,58].…”

“…3a and 4a). In various TMDs [4,58,61], defects of this type are the most abundant and produce electron trap states within the band gap.…”

“…Defects of type A are indeed from one missing atom at the topmost Se layer, V Se1a , clearly seen in both experimental images and integrated LDOS (figures 3(a) and 4(a)). In various TMDs [4,22,59,63,64], defects of this type are the most abundant and produce electron trap states within the band gap. In our experiments, almost all the type A defects are isolated.…”

Recent advances in defect electrocatalysts: Preparation and characterization

“…Scanning tunneling microscopy (STM) has been used to examine single crystal surfaces and revealed that structural defects, such as vacancies, substitutional or interstitial impurities, are regions of absorptive binding for gases and ions; therefore, they are considered active sites for catalysis [137][138][139]. For example, as shown in Fig.…”