Preparation of light-atom tips for Scanning Probe Microscopy by explosive delamination

TL;DR

This paper introduces a novel method for preparing clean, oxide-free beryllium tips for STM and AFM, enhancing resolution by minimizing tip orbital size and ensuring tip stability.

Contribution

A new preparation technique combining field emission heating and mild collision effectively produces clean beryllium tips suitable for high-resolution microscopy.

Findings

Successfully removes oxide layer from beryllium tips

Achieves a work function indicating a clean surface

Demonstrates single-atom tip termination with STM imaging

Abstract

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.