To obtain maximal resolution in STM and AFM, the size of the protruding tip orbital has to be minimized. Beryllium as tip material is a promising candidate for enhanced resolution because a beryllium atom has just four electrons, leading to a small covalent radius of only 96 pm. Besides that, beryllium is conductive and has a high elastic modulus, which is a necessity for a stable tip apex. However beryllium tips that are prepared ex situ, are covered with a robust oxide layer, which cannot be removed by just heating the tip. Here we present a successful preparation method that combines the heating of the tip by field emission and a mild collision with a clean metal plate. That method yields a clean, oxide-free tip surface as proven by a work function of as deduced from a current-distance curve. Additionally, a STM image of the Si-(111)-(7x7) is presented to prove the single-atom termination of the beryllium tip.
@article{arxiv.1001.1321,
title = {Preparation of light-atom tips for Scanning Probe Microscopy by explosive delamination},
author = {Thomas Hofmann and Joachim Welker and Franz J. Giessibl},
journal= {arXiv preprint arXiv:1001.1321},
year = {2015}
}