Wide range local resistance imaging on fragile materials by conducting probe atomic force microscopy in intermittent contact mode

Abstract

An imaging technique associating a slowly intermittent contact mode of atomic force microscopy (AFM) with a home-made multi-purpose resistance sensing device is presented. It aims at extending the widespread resistance measurements classically operated in contact mode AFM to broaden their application fields to soft materials (molecular electronics, biology) and fragile or weakly anchored nano-objects, for which nanoscale electrical characterization is highly demanded and often proves to be a challenging task in contact mode. Compared with the state of the art concerning less aggressive solutions for AFM electrical imaging, our technique brings a significantly wider range of resistance measurement (over 10 decades) without any manual switching, which is a major advantage for the characterization of materials with large on-sample resistance variations. After describing the basics of the set-up, we report on preliminary investigations focused on academic samples of self-assembled monolayers with various thicknesses as a demonstrator of the imaging capabilities of our instrument, from qualitative and semi-quantitative viewpoints. Then two application examples are presented, regarding an organic photovoltaic thin film and an array of individual vertical carbon nanotubes. Both attest the relevance of the technique for the control and optimization of technological processes.

Electromechanical conversion efficiency of GaN NWs: critical influence of the NW stiffness, the Schottky nano-contact and the surface charge effects

“…1a) inspired by the so-called ‘pulsed force mode’ (PFM), a low frequency non-resonant mode originally developed for local mechanical measurements. 43 On this method, some modifications have been performed in order to allows us quantifying the piezoelectric response of individual NWs under a well-controlled and purely axial force. Where the z -piezo supports the NW sample, the technique consists in introducing a sinusoidal modulation on the AFM z -piezo at a frequency between 100 Hz and 2 kHz ( i.e.…”

Current measurements in the intermittent-contact mode of atomic force microscopy using the Fourier method: a feasibility analysis

“…A notable example is the work by Fein et al where injected voltage pulses were investigated using a custom-made, low-frequency, high-stiffness cantilever [22]. Another example is the work of Vecchiola et al where a "pulsed force" microscopy approach was implemented, rather than traditional ICM-AFM [23]. Although the end result was intermittent-contact characterization, due to the nature of the force pulses the probe jumped from contact point to contact point rather than exhibiting a constant, nearly resonant intermittent-contact oscillation (the oscillation frequencies used were much smaller than the resonance frequency of the cantilever).…”