Reliable tip preparation for high-resolution scanning tunneling microscopy

Abstract

We describe a method to prepare electron emitters (tips) designed to achieve routine atomic resolution in a scanning tunneling microscope. Highly reliable results were obtained with repeated sputter-anneal processes in ultrahigh vacuum using polycrystalline tungsten wires as the base material. A tip apex radius of less than 5 nm and an atomic resolution of III–V (110) semiconductor surfaces are routinely obtained. The analysis involves scanning electron microscopy, transmission electron microscopy, scanning tunneling microscopy, and current–voltage characteristics in the field emission regime.