Scanning tunneling microscope modifications of amorphous Ge-Sb-Te films

Surface modifications produced in Ge-Sb-Te films by a scanning tunneling microscope have been studied. Three kinds of modifications appear depending upon applied voltages to the tip. Positive tip voltages of about 2 V produce depressions accompanying peripheral mounds, which can be accounted for as mechanical scratching by the tip. When humidity is higher than similar to50 %, tip voltages between 5 and 10 V produce depressions with no peripheral mounds, and negative tip voltages of about -10 V produce expansions, which are identified as Sb2O3 from Raman scattering spectra. These humidity-assisted depression and expansion are assumed to be caused by electrochemical etchings and anodic oxidation processes.