Nanostructure formation on amorphous WO3 thin films in air by scanning tunneling microscopy

H. Qiu, Y. F. Lu, Z. H. Mai

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


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 languageEnglish (US)
Pages (from-to)290-294
Number of pages5
JournalJapanese Journal of Applied Physics
Issue number1
StatePublished - Jan 2001
Externally publishedYes


  • Bump
  • Electric field gradient
  • Electrochemistry
  • Hole
  • Humidity

ASJC Scopus subject areas

  • General Engineering
  • General Physics and Astronomy


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