title: Safe fabrication of sharp gold tips for light emission in scanning tunnelling microscopy.
abstract: Gold is the optimal tip metal for light emission in scanning tunnelling microscopy (LESTM) under ambient conditions. Sharp Au-tips of approximately 10 nm radius were produced reliably using a safe, two-step etching method in 20% (w/w) CaCl2 solution. Previous CaCl2-based methods have tended to produce blunter tips, while other etching techniques that do produce sharp Au-tips, do so with the use of toxic or hazardous electrolytes. The tips are characterised using scanning electron microscopy and their efficacy in LESTM is evidenced by high-resolution, simultaneous topographic and photon mapping of Au(111)- and polycrystalline Au-surfaces. Spectra of the optical emission exhibit only one or two peaks with etched tips in contrast to the more complex spectra typical of cut tips; this feature, together with the highly symmetric geometry of the tips, facilitates a definitive analysis of the light emission process.
authors.affiliation: Centre for Nanostructured Media, International Research Centre for Experimental Physics, Queen's University of Belfast, Belfast BT7 1NN, UK.
authors.forename: Michael G
authors.initials: MG
authors.lastname: Boyle
authors.forename: Lei
authors.initials: L
authors.lastname: Feng
authors.forename: P
authors.initials: P
authors.lastname: Dawson