STM-MEDIATED SURFACE DEGRADATION ON 1T-TAS2

Investigating 1T-TaS2 with an STM we found that its bulk hexagonal lat tice bears the inherent tendency to a slow and irregular degradation o f the surface. The onset of this degradation is triggered by any elect rical current above a minimum density. This current may be due to the STM scanning process itself, but degradation can also be achieved by a current generated by a gross voltage applied externally across the sa mple. Scan holes, which were observed in accordance with earlier repor ts, display geometric rather than irregular structures, and their grow th is considerably accelerated with constant-height scans. Most probab ly they are formed via abrasion with the tip, which primarily removes surface atoms at sites with lattice defects or surface steps. Local th ermal-heating, electrical-field and/or gradient effects do not play an y significant role in these degradation processes. The ease by which t he surface atoms are manipulated indicates that the phenomenon of scan holes also seems to be intimately linked to the metastability of the 1T-TaS2 surface lattice.