Light emission from scanning tunnelling microscope on polycrystalline Au films - what is happening at the single-grain level?

Paul Dawson, Michael Boyle

Research output: Contribution to journalArticle

21 Citations (Scopus)

Abstract

When operated with a metallic tip and sample the scanning tunnelling microscope constitutes a nanoscale, plasmonic light source yielding broadband emission up to a photon energy determined by the applied bias. The emission is due to tunnelling electron excitation and subsequent radiative decay of localized plasmon modes, which can be on the lateral scale of a single metal grain (similar to 25 nm) or less. For a Au-tip/Au-polycrystalline sample under ambient conditions it is found that the intensity and spectral content of the emitted light are not dependent on the lateral grain dimension, but are predominantly determined by the tip geometry. However, the intensity increases strongly with increasing film thickness (grain depth) up to 20-25 nm or approximately the skin depth of the Au film. Photon maps can show less emissive grains and two classes of this occurrence are distinguished. The first is geometrical in origin - a double-tip structure in this case - while the second is due to a contamination-induced lowering of the local work function that causes the tunnel gap to increase. It is suggested that differences in work-function lowering between grains presenting different crystalline facets, combined with an exponential decay in emitted light intensity with tip - sample distance, leads to grain contrast. These results are relevant to tip-enhanced Raman scattering and the fabrication of micro/nano-scale planar, light-emitting tunnel devices.
Original languageEnglish
Pages (from-to)S219-S226
Number of pages8
JournalJournal of Optics A: Pure and Applied Optics
Volume8(4)
Issue number4
DOIs
Publication statusPublished - 01 Jan 2006

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics

Fingerprint Dive into the research topics of 'Light emission from scanning tunnelling microscope on polycrystalline Au films - what is happening at the single-grain level?'. Together they form a unique fingerprint.

  • Cite this