Spatial Correlation between Fluctuating and Static Fields over Metal and Dielectric Substrates

Abstract

We report spatially resolved measurements of static and fluctuating electric fields over conductive (Au) and nonconductive (SiO 2 ) surfaces. Using an ultrasensitive "nanoladder" cantilever probe to scan over these surfaces at distances of a few tens of nanometers, we record changes in the probe resonance frequency and damping that we associate with static and fluctuating fields, respectively. We find static and fluctuating fields to be spatially correlated. Furthermore, the fields are of similar magnitude for the two materials. We quantitatively describe the observed effects on the basis of trapped surface charges and dielectric fluctuations in an adsorbate layer. Our results are consistent with organic adsorbates significantly contributing to surface dissipation that affects nanomechanical sensors, trapped ions, superconducting resonators, and color centers in diamond.

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“…6. We note that the numbers and the spatial distribution recovered here are different from those seen with a nanoladder cantilever over flat surfaces [44]. Here, the dissipative and conservative forces over the magnet vary over ranges of several 100 nm and they have different spatial signatures.…”

“…Here, the dissipative and conservative forces over the magnet vary over ranges of several 100 nm and they have different spatial signatures. We also note that the non-contact damping coefficient is orders of magnitudes larger than in our previous experiments [44], which is a result of the much larger apex of the cantilever used in this study.…”

“…This, however, makes it also sensitive to arbitrary surface forces that create instabilities and obstruct the collection of data in certain regions of space. We can at present not identify the microscopic origin of these forces with certainty, but because of their long-range characteristics, it is likely that they are related to trapped charges at the interface between the nanomagnet and the microstrip antenna [44].…”

“…Dissipative non-contact forces have been the subject of intense research efforts for more than two decades [34][35][36][37][38][39][40][41][42][43][44]. By reducing the quality factor of a resonator, dissipation generally impedes a sensor's ability to detect small forces.…”

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“…Alternatively, AFM, a standard tool to investigate surface roughness of thin films and substrates, can image any surface. State-of-the-art techniques can probe the connection between surface dissipation and static variations in the surface potential [125], which might link to surface TLS. An advantage of AFM is that it can be combined with a wide range of other techniques and readout schemes, where the AFM is mainly used to maintain a constant tip-sample separation.…”