Nanoscale Imaging of Phase Transitions with Scanning Force Microscopy

TLDR: In this paper, a method to control the quality factor of a conducting cantilever via capacitive coupling to the local environment was proposed, which can enhance force-gradient sensitivity or scan speed.

Abstract: Nanoscale imaging of materials through phase transitions can provide valuable insight into the local nature of the transition and the emergence of order. The scanning force microscope used in the studies presented here is an ideal instrument to investigate phase transitions with nanoscale spatial resolution. We study phase transitions in two different systems by operating in different modes: contact mode, in which we measure the local electronic properties of the sample; and non-contact mode, in which we probe the sample by monitoring the interaction between the sample and cantilever. We increased the versatility of this microscope by developing a method to control the quality factor Q of a conducting cantilever via capacitive coupling to the local environment. We show that Q may be reversibly tuned over a range of a factor of 260. We describe the underlying physics with a point-mass oscillator model. Tuning Q can enhance force-gradient sensitivity or scan speed, which we demonstrate with topographic scans of a VO2 acquired in high vacuum. Scanning in contact mode with a conductive cantilever, we study local electronic properties of a vanadium dioxide (VO2) thin film through an insulator to metal transi-