Open-loop amplitude-modulation Kelvin probe force microscopy operated in single-pass PeakForce tapping mode.

Gheorghe Stan,Pradeep Namboodiri

doi:10.3762/bjnano.12.83

Gheorghe Stan, Pradeep Namboodiri

Open Access

PDF Available

https://doi.org/10.3762/bjnano.12.83

Copy DOI

Export

Save

Cite

Abstract
Highlights/Summary
Full-Text PDF
Similar Papers

Abstract

Listen

The open-loop (OL) variant of Kelvin probe force microscopy (KPFM) provides access to the voltage response of the electrostatic interaction between a conductive atomic force microscopy (AFM) probe and the investigated sample. The measured response can be analyzed a posteriori, modeled, and interpreted to include various contributions from the probe geometry and imaged features of the sample. In contrast to this, the currently implemented closed-loop (CL) variants of KPFM, either amplitude-modulation (AM) or frequency-modulation (FM), solely report on their final product in terms of the tip–sample contact potential difference. In ambient atmosphere, both CL AM-KPFM and CL FM-KPFM work at their best during the lift part of a two-pass scanning mode to avoid the direct contact with the surface of the sample. In this work, a new OL AM-KPFM mode was implemented in the single-pass scan of the PeakForce Tapping (PFT) mode. The topographical and electrical components were combined in a single pass by applying the electrical modulation only in between the PFT tip–sample contacts, when the AFM probe separates from the sample. In this way, any contact and tunneling discharges are avoided and, yet, the location of the measured electrical tip–sample interaction is directly affixed to the topography rendered by the mechanical PFT modulation at each tap. Furthermore, because the detailed response of the cantilever to the bias stimulation was recorded, it was possible to analyze and separate an average contribution of the cantilever to the determined local contact potential difference between the AFM probe and the imaged sample. The removal of this unwanted contribution greatly improved the accuracy of the AM-KPFM measurements to the level of the FM-KPFM counterpart.

Highlights

Over many years, an abundance of developments and applications has made Kelvin probe force microscopy (KPFM) [1] one of the most versatile nanoscale surface electronic characterization techniques
The new OL AM-KPFM implementation was tested on a commercially available sample consisting of large Au and Al metal regions deposited on a Si substrate (Bruker Nano Surfaces, Santa Barbara, CA, USA); the metal regions are separated by trenches that expose the Si substrate at their bottom
The contact potential difference (CPD) maps over the sample were obtained first by using two common CL KPFM modes that are implemented on PeakForce Tapping (PFT), namely CL AM-KPFM and CL FM-KPFM [57]

Summary

Introduction

An abundance of developments and applications has made Kelvin probe force microscopy (KPFM) [1] one of the most versatile nanoscale surface electronic characterization techniques. Because the response to the applied bias modulation was fully acquired in the proposed OL KPFM implementation, the CPD was determined by modeling the electrostatic interaction between the AFM probe and the sample.

Results

Conclusion