Note: Switching crosstalk on and off in Kelvin probe force microscopy

Abstract

In Kelvin Probe Force Microscopy (KPFM) electronic crosstalk can occur between the excitation signal and probe deflection signal. Here, we demonstrate how a small modification to our commercial instrument enables us to literally switch the crosstalk on and off. We study in detail the effect of crosstalk on open-loop KPFM and compare with closed-loop KPFM. We measure the pure crosstalk signal and verify that we can correct for it in the data-processing required for open-loop KPFM. We also demonstrate that open-loop KPFM results are independent of the frequency and amplitude of the excitation signal, provided that the influence of crosstalk has been eliminated.

Quantitative comparison of closed-loop and dual harmonic Kelvin probe force microscopy techniques

“…In practice however, 1/V ac and C Z dependencies are often observed. 7,27,29 In fact, the CPD values determined using traditional KPFM are influenced by a variety of factors: Instrumentation effects include electronic offsets and cross talk (between V ac and the photodetector output and/or between V ac and the piezoactuator), 4,7,35,38 thermomechanical and electrical noise sources, 39,40 the choice of feedback gains, 26,27 the choice of V ac frequency, and lock-in amplifier phase offset. 7,14,28,29 The net effect of these factors is that the input signal to the feedback loop contains contributions, which are not associated with the electrostatic tip-sample forces.…”

“…Electronic offsets and electronic cross talk, if present, can also affect CPD values determined by DH-KPFM. 7,35 However, since there is no feedback loop present in DH-KPFM, there is no error associated with loop gains or trying to minimize a mixed signal (i.e., the feedback effect). 4,35…”

“…8 Open-loop KPFM (OL-KPFM) techniques are increasingly being adopted as feedback-free methods, 7,9,[18][19][20][10][11][12][13][14][15][16][17] eliminating the need for the application of a DC bias 7 and enabling the mapping of voltage-sensitive materials 9,15,21,22 and surface potentials in liquid environments. [10][11][12]16,17,[23][24][25] These techniques are also of interest for their reduced sensitivity to electronic offsets and electronic cross talk instrumentation a) Authors to whom correspondence should be addressed: jason.kilpatrick@ ucd.ie and brian.rodriguez@ucd.ie issues, 4,7,[32][33][34][35]13,22,[26][27][28][29][30][31] which can affect both OL-and CL-KPFM operation to varying degrees. 35 Dual harmonic KPFM (DH-KPFM) is one example of OL-KPFM which has been utilized to measure surface potential 7,[9][10]…”

“…[10][11][12]16,17,[23][24][25] These techniques are also of interest for their reduced sensitivity to electronic offsets and electronic cross talk instrumentation a) Authors to whom correspondence should be addressed: jason.kilpatrick@ ucd.ie and brian.rodriguez@ucd.ie issues, 4,7,[32][33][34][35]13,22,[26][27][28][29][30][31] which can affect both OL-and CL-KPFM operation to varying degrees. 35 Dual harmonic KPFM (DH-KPFM) is one example of OL-KPFM which has been utilized to measure surface potential 7,[9][10][11][12]15,16,25,35,36 in ultrahigh vacuum, 9,36 air, 7,15,35 and liquid [10][11][12]16,25 environments.…”

Kelvin probe force microscopy for local characterisation of active nanoelectronic devices

“…Such crosstalk is due to parasitic capacitive coupling and observed mainly in AM-KFM, where the electrostatic modulation is at high frequencies [32]. When coupling to the shaker piezo [33], cantilever resonances can amplify this effect.…”