Electrical Stressing Induced Monolayer Vacancy Island Growth on TiSe2

TL;DR

This study investigates how electrical stressing via STM causes shape evolution and growth of vacancy monolayer islands on TiSe2, revealing a linear growth rate and edge atom dissociation, with implications for 2D material device stability.

Contribution

First observation of shape evolution and growth of vacancy islands on TiSe2 under electrical stressing, supported by phase-field modeling and analysis of growth mechanisms.

Findings

Island size grows linearly at 3.00 x 10^-3 nm/s under fixed STM parameters.

Growth rate depends on tunneling current magnitude.

Phase-field simulations agree with experimental growth behavior.

Abstract

To ensure the practical application 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 TiSe2 surfaces as a model system, for the first time we have observed a shape evolution and growth from triangular to hexagonal driven by scanning tunneling microscopy (STM) electrical stressing. The size of islands shows linear growth with a rate of (3.00 +- 0.05) x 10-3 nm/s, when the STM scanning parameters are held fixed at Vs = 1.0 V and I = 1.8 nA. We further quantified how the growth rate is related to the tunneling current magnitude. Our simulations of monolayer island evolution using phase-field modeling are in good agreement with our experimental observations, and point towards preferential edge atom dissociation under STM scanning driving the observed growth. The results could be potentially important for device applications of ultrathin transition metal dichalcogenides and related 2D materials subject to electrical stressing under device operating conditions.