STM and XPS study of filtered vacuum arc deposited Sn-O films

L. Kaplan*, I. Rusman, R. L. Boxman, S. Goldsmith, M. Nathan, E. Ben-Jacob

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Highly conductive, transparent films were fabricated by filtered vacuum arc deposition, followed by rapid thermal annealing (RTA) at 300°C for 30 s. Low temperature measurements of resistance versus temperature demonstrated metallic conduction in the films. Scanning tunneling microscopy/spectroscopy (STM/SPS) showed that the films obtained under optimal conditions were highly homogeneous and had degenerate semiconductor characteristics. However, if the arc had even short periods of unstable operation, then non-degenerate semiconductor regions were also found. The average heights of the crests on the as-deposited films depended on their thickness, being 5, 2 and 0.6 nm for the 50, 350 and 450 nm thick layers, respectively. RTA decreased the crest heights. Well-separated clusters of amorphous tin oxide having typical lateral dimensions of 10 × 4 nm and a height of 6 nm were observed in the thin 50 nm films. The STM topographic images of films after annealing showed clusters with lateral dimensions of 40 × 40 nm and a height of 3 nm, probably originating from the merging of the previously described narrower grains. If non-degenerate semiconductor clusters with wide band gaps were in the as-deposited film, they remained after RTA. It is presumed that these non-degenerate clusters were SnO rather than SnO2, and that they are responsible for the poor conductivity of these films. X-ray Photoelectron Spectroscopy (XPS) showed that the oxygen concentration of the film did not change after annealing. There were many occupied states in the band gaps of both the as-deposited and annealed samples (in the energy range 0-5 eV), which, however, had different energy distributions. The RTA induced relaxation increased the short range ordering, and led to cluster growth in the films. These changes freed trapped electrons, and increased their mobility.

Original languageEnglish
Pages (from-to)355-361
Number of pages7
JournalThin Solid Films
Volume290-291
DOIs
StatePublished - 15 Dec 1996

Keywords

  • Filtered vacuum arc
  • Tin oxide
  • Transparent conductive oxide

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