Field-induced surface modification on the atomic scale by scanning tunneling microscopy

Scanning tunneling microscopy has been used to study the modification of tin diselenide (SnSe2) and molybdenum disulfide (MoS2) surfaces in ultrahigh vacuum. We have shown that there are positive bias voltage pulse thresholds that must be exceeded to remove material from the surfaces of SnSe2 and MoS2. The voltage threshold for modification of SnSe2(+1.4 V) is significantly smaller in magnitude than the threshold for modification of MoS2(+3.5 V). These threshold results and tip-sample distance dependence data suggest that modification occurs by field evaporation. Additionally, near threshold pulses create stable atomic sizes defects that can be erased by high voltage scanning.