Carbon-based materials such as diamond-like carbon (DLC) thin films and carbon nanotubes are attracting a great deal of attention due to their novel and versatile properties and likely applications. In particular, good chemical stability has been ascribed to these materials. Recently it has been shown that DLC can be patterned on the nm-scale by local electro-oxidation in a humid environment, where localization is defined by either 'tunnel' current or spreading current in STM or AFM modes (Scanning Tunnelling and Atomic Force Microscopy), respectively. The process has now been extended to oxidative patterning of DLC films and carbon nanotubes in an environmental SEM in the presence of 10-100 Pa of water pressure.
Examples for nano-patterning of filled multi-walled carbon nanotubes and of DLC thin films, both on substrates and self-supporting, will be presented. Preliminary data suggests that the reaction rate of the SEM-based process is linearly dependent on beam current, while the dependence on partial pressure of water has a minor effect. On the other hand, the kinetics and efficiency of the STM-based technology is strongly dependent on relative humidity, tip-to-sample bias and surface-chemistry.
The SEM-based technology has the potential for being a reliable and convenient method for nm-scale 3-dimensional patterning of self-supporting carbon-based materials.
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