Aspects of nanotechnology

There are three possible ways of structuring surfaces: (1) positive (deposition), (2) negative (etching or mechanical removal) and (3) modification (implantation). An example of (1) is given by Sugimura et al. [10, 11]: Structures with xy dimensions of 2050 nm and z dimensions of 1-5 nm could be generated by applying high positive bias voltages (STM-experiments in wet air) on silicon and titanium. Standard STM pictures could be obtained by using negative voltages on highly n-doped silicon and on hydrogen-saturated titanium dioxide. When the voltage was changed to highly positive values (+5-8V), then the surface was modified. This modification was monitored by changing back to a negative bias or by AFM. If the STM tip was moved over the surface during the period of positive bias, then a modification trace was left on the surface. These modifications were discussed as anodically grown oxide. The wet air leaves a thin water film on the substrate. This water is used for the oxidation of the surface during the application of a high electric positive field. Laser-induced oxide growth on titanium and silicon was first observed by Schultze and coworkers [12-14]. In addition, Ag traces could be measured with laser-light in AgN03/Me0H solution [15]. These structures have z dimensions of only 10-100 nm. In this paper, we demonstrate the investigation of thin, well defined, anodically grown TiC>2 films with SPM techniques. In addition, we discuss aspects (2) and (3): removal of TiC>2 by STM, and modification by nitrogen implantation.

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