A dynamic-difference approach to scan probe microwave reflectivity mapping of the nanoscale electronic properties of single-walled carbon nanotubes

摘要

Understanding carbon nanotubes (CNTs) based electronic devices requires strategies to characterize individual nanotube electronic properties. We will explore a new nonevasive approach to microwave impedance microscopy (MIM) which, we hypothesize, utilizes the ambient water layer as a nanoscale high permittivity medium. This approach eliminates the need for a thin metal oxide surface layer, used in contact mode MIM-AFM of CNTs, which completely obscures resistance mapping and can increase surface roughness by 10x. The potential novelty of our proposed MIM methodology is that the water meniscus, known to form beneath the tip, creates a localized high permittivity environment between the tip and the surface. The materials microwave response image is extracted from the "capacitive difference" observed on trajectories' measures via the transmission line cantilever during approach. We can mechanically detect the water meniscus formation using AFM force curves while simultaneously mapping resistance, capacitance, and topography. When comparing signal-to-noise (SNR), to contact MIM-AFM, our results suggest a 2x increase in MIM capacitance SNR, 10-100x improvement in MIM resistance SNR, and up to 3x increase in the capacitance mapping resolution by reducing the effects of tip-surface spatial convolution. Published under license by AIP Publishing.