Microfabrication of silicon tip structures for multiple-probe scanning tunnelling microscopy

We report the fabrication of arrays of silicon tips suitable for multiple-tip scanning tunneling microscopy applications (STM). We have produced silicon tips by reactive ion etching using only photoresist masks, removing, the need for the extra processing required to produce oxide masks. These tips have been oxide-sharpened to reduce their radius of curvature to less than 10 nm. Metallic coating of the tips makes them suitable for STM measurements, by the addition of an appropriate metallic layer. The use of thick resist layers makes it possible to protect the tips during further processing such that they have been integrated on 20 mum mesa structures. Further patterning of thick resists over these structures enables individual contact to be made to the tips via lift-off. We have also produced single silicon tips suitable for STM by selecting individual tips from arrays. Images of grating structures shows these tips have well defined tip shape compared with STM tips produced by conventional methods, while atomic resolution STM measurements have also been obtained. (C) 2002 American Vacuum Society.