High resolution dynamic electrostatic force microscopy technique: quantifying electrical properties at the nanoscale.
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High resolution dynamic electrostatic force microscopy technique: quantifying electrical properties at the nanoscale. C. Maragliano, D. Heskes, M. Stefancich, M. Chiesa and T. Souier LENS Laboratory @ Institute Center for Future Energy Systems (iFES), Masdar Institute of Science and Technology, P.O.Box 54224, Abu Dhabi, UAE
Abstract In electrostatic force microscopy (EFM), a conductive atomic force microscopy (AFM) tip is electrically biased against a grounded sample and electrostatic forces are investigated. This methodology has been broadly used in the scientific community to characterize dielectric properties of samples at the nanoscale. Two are the main operating conditions associated with this technique. The oscillation amplitude is usually kept to very small values to allow a linearized approach to the force reconstruction and the tip-sample distance is maintained elevated. However, this latter condition negatively affects the lateral resolution of the technique. Thus, electrostatic interaction should be probed in the vicinity of the sample. Theoretically, in this region the force can be linearized using oscillation amplitudes in the order of Å. This might cause the trapping of the tip on the surface (snap-in). Furthermore, at small distances, short-range forces (i.e. Van der Waals’) might reach values comparable to electrostatic forces. Here we present a framework that combines EFM and dynamic amplitude modulation AFM to achieve decoupled reconstruction of forces. It permits reconstructing the real shape of the electrostatic force and the capacitance of the tip-sample system even in the vicinity of the surface. This is done using a technique proposed in literature by Sader and Katan to reconstruct the force without the linearization approximation. The steps needed to decouple short-range and electrostatic forces are explained in detail. This data can be employed to derive the electrical properties of thin films with enhanced lateral resolution with respect to the commonly used EFM techniques.
Introduction Quantifying long-range electrostatic interaction forces between nanometric objects is of great importance in nanotechnology. Electrostatic forces are related to the intrinsic dielectric properties of materials and therefore the quantification of such forces would provide a means for
sample electrical characterization. With the increasing use of confined structures in electronics and optoelectronics[1], the need for a technique able to measure dielectric properties of materials (i.e. dielectric constant) at the nanoscale is becoming pressing. The advent of such technique could also represent an important alley for the understanding of nanoscale electrostatic interaction in molecules[2] and membranes[3, 4], where the need of high spatial resolution is critical. Being a force-based technique and given its intrinsic high spatial resolution[5], AFM is one of the most suitable candidates capable of addressing the above mentioned need. Different AFMbased techniques have been recently proposed for the characteri
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