High aspect ratio cantilever tips for non-contact electrostatic force microscopy

Abstract

This work focuses on the atomic force microscope: its hardware, modes of operation, and applications.The construction of a x-y sample positioner, equipped with position dependent capacitive sensor, is presented. The implementation of a temperature-controlled laser for cantilever detection, via interferometry, is also discussed.Two modes of atomic force microscopy are used. Amplitude modulation mode images are done in vacuum using Q-control to reduce the apparent Q-factor of the cantilever. Frequency modulation mode is used to obtain non-contact images and force curves above a quantum dot or gold sample. The former leads to detection of single electron charging events from a buried 2D electron gas to the surface layer of the sample. The latter was done to determine the geometric behaviour and capacitance of high-aspect ratio cantilever tips; a method for which is presented where the height, cone angle, radius of curvature and angle to the sample can be controlled