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Abstract:
Investigating 1T-TaS2 with an STM we found that its bulk hexagonal
lattice bears the inherent tendency to a slow and irregular degradation
of the surface. The onset of this degradation is triggered by any
electrical 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
sample. Scan holes, which were observed in accordance with earlier
reports, display geometric rather than irregular structures, and their
growth is considerably accelerated with constant-height scans. Most
probably they are formed via abrasion with the tip, which primarily
removes surface atoms at sites with lattice defects or surface steps.
Local thermal-heating, electrical-field and/or gradient effects do not
play any significant role in these degradation processes. The ease by
which the 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.
