Scanning tunneling electron microscopy (STM) has recently shown great promise for surface modification in the nanometer regime. As is well known, the normal STM tips are easily damaged by mechanical contact with the sample surface in most cases. In this paper we describe a new type of diamond STM tip prepared by the microwave plasma chemical vapor deposition technique. The reactant is a gas mixture of methane and hydrogen. Diamond crystals are grown on a tungsten tip. The diamond tips are very hard and always have enough electrical conductivity for STM experiments. They can be used as a machining tool to scratch the metal surfaces.
Kinetic roughening of tantalum films during the initial growth stages has been studied by atomic force microscopy, scanning electron microscopy, and dynamic scaling theory. Different from the time-independent scaling behavior for continuous film growth, an intriguing unstable kinetic roughening occurs during island coalescence. In such case, roughness exponent α increases with growth time, accompanied by lower growth exponent β and higher coarsening exponent η. Detailed analysis of film surface morphology and simple phenomenological models suggests that this unstable behavior is related to the pronounced lateral growth of surface islands, which arises from the combined effect of the formation of grain boundary and the covering of heterogeneous substrate surface.
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