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

H. Qiu, Yongfeng Lu, Z. H. Mai

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

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, Part 1: Regular Papers and Short Notes and Review Papers
Volume40
Issue number1
DOIs
StatePublished - Jan 1 2001

Fingerprint

Scanning tunneling microscopy
Amorphous films
scanning tunneling microscopy
Nanostructures
Atmospheric humidity
humidity
Thin films
air
Electric potential
Microscopes
thin films
Air
Electric fields
Scanning
electric potential
pulses
microscopes
Threshold voltage
scanning
electric fields

Keywords

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

ASJC Scopus subject areas

  • Engineering(all)
  • Physics and Astronomy(all)

Cite this

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abstract = "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.",
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