High Resolution Non-contact Atomic Force Microscopy on surfaces with the fluorite structure

Abstract

Non-contact atomic force microscopy (NC-AFM) high-resolution imaging on the fluorite surfaces is investigated. The principles underlying NC-AFM operation are discussed. The ultra-high vacuum (UHV) NC-AFM experimental setup, system modifications for optimised system performance, are described. A systematic approach based on the RHK Beetle UHV VT AFM system to determine the in-plane crystallographic surface directions in SPM images is presented and demonstrated by determining the [11-2] direction in topographic images of a CeO2(111) film grown on a Si(111) wafer and atomic resolution images of CaF2(111). A qualitative symmetry-based combinatorial approach to unambiguously identify the three sublattices of the CaF2(111) surface and the tip-polarity responsible for atomic contrast is introduced. Additionally, the impact of tip changes on atomic scale NC-AFM contrast is analysed, showing that atomic contrast change arises from either a polarity change of the tip terminating cluster or a polarity-preserving tip change. The morphology and growth mechanism of gold (Au) clusters on the CaF2(111) surface are investigated