Implementation of atomically defined Field Ion Microscopy tips in Scanning Probe Microscopy

TL;DR

This paper presents a protocol for preserving atomically defined tips from FIM in SPM, demonstrating their stability and limitations during tunneling experiments at room temperature.

Contribution

A novel protocol to maintain atomic tip structure during transfer from FIM to SPM and analysis of surface interactions affecting tip stability.

Findings

Atomic tips remain stable on Si(111) surface.

Gas contamination limits tip preservation.

Tip integrity is compromised by adatom mobility on certain surfaces.

Abstract

The Field Ion Microscope (FIM) can be used to characterize the atomic configuration of the apex of sharp tips. These tips are well suited for Scanning Probe Microscopy (SPM) since they predetermine SPM resolution and electronic structure for spectroscopy. A protocol is proposed to preserve the atomic structure of the tip apex from etching due to gas impurities during the transfer period from FIM to SPM, and estimations are made regarding the time limitations of such an experiment due to contamination by ultra-high vacuum (UHV) rest gases. While avoiding any current setpoint overshoot to preserve the tip integrity, we present results from approaches of atomically defined tungsten tips to the tunneling regime with Au(111), HOPG, and Si(111) surfaces at room temperature. We conclude from these experiments that adatom mobility and physisorbed gas on the sample surface limit the choice of surfaces for which the tip integrity is preserved in tunneling experiments at room temperature. The atomic structure of FIM tip apices is unchanged only after tunneling to the highly reactive Si(111) surface.