Voltage fluctuations and probe frequency jitter in electric force microscopy of a conductor.

This article focuses on calculating the frequency jitter power spectrum and noncontact friction in electric force microscopy (EFM) measurements over conducting samples of finite thickness characterized by a wavevector-dependent dielectric function. Using the Lindhard–Mermin dielectric function to model conduction electron dynamics in metals such as gold, the study presents numerical results showing that both finite sample thickness and wavevector-dependent dielectric response can significantly enhance predicted electric field fluctuations and jitter spectra compared to simpler dielectric continuum models. The work relates EFM observables—noncontact friction and probe frequency jitter—to equilibrium autocorrelation functions of electric field fluctuations and gradients, providing a formalism to compute these quantities from the Fresnel reflection coefficient at the sample–vacuum interface. Despite these enhancements, the predicted jitter magnitudes for clean metal films remain below typical experimental detection limits due to thermal noise, suggesting that electronic excitations in metals without adsorbates contribute less to EFM noise than molecular samples.