Scanning tunnelling microscope (STM) modifications on α-WO3-x thin films were carried out in air. Holes and bumps were produced. Two mechanisms were clarified with respect to the water layer attached more or less in modifications. By applying voltage pulses, the high humidity (>60%) raised the probability of hole formations. Connection lines were formed between the holes, confirming a dominant electrochemical nature. The low humidity (<20%) raised the probability of bump formations. Similar heights in both STM and atomic force microscopy (AFM) images imply a physical transformation in the process. Depressed sides near the bumps strongly manifested the diffusion of surface molecules to the tip induced by the electric field gradient. In the intermediate humidity (20-60%), there was a higher voltage threshold for bump formations than for hole formations, as well as for positive voltage pulses than for negative voltage pulses. The discrepancies were reasonably attributed different tip-sample distances and the consequently induced electric fields.
|Original language||English (US)|
|Number of pages||5|
|Journal||Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers|
|State||Published - Jan 2001|
- Electric field gradient
ASJC Scopus subject areas
- Physics and Astronomy(all)