IMPROVED ATOMIC FORCE MICROSCOPE IMAGES USING MICROCANTILEVERS WITH SHARP TIPS

Novel force-sensing microcantilevers with sharp tips have been used to obtain atomic force microscope images of atomically flat, layered compounds as well as microfabricated samples with large-scale topographies. When imaging atomically flat samples using cantilevers with sharp protruding tips, atomic corrugations are observed more consistently and with a higher signal-to-noise ratio than in the absence of tips. Some asymmetric distortions arise when tipped cantilevers are used with forces larger than 10-7 N. Side by side comparisons of images of rough samples obtained using cantilevers with and without tips reveal that the presence of a sharp tip yields superior image quality of vertical features and trenches. The cantilever assembly is a microfabricated, silicon nitride cantilever with an integral, single-crystal silicon tip. The silicon tip is self-aligned to the end of the cantilever and is created by a process which simultaneously fabricates and sharpens the silicon tip. Initial transmission electron microscopy studies show that the single-crystal silicon tips have radii of curvature of 220-400 Å.