SPM Investigations on Oxidecovered Titanium Surfaces Problems and Possibilities

Contents

1 Introduction 226

1.1 Methods 226

1.2 Role of the sample preparation and measurements conditions 228

1.3 Aspects of nanotechnology 228

2 Experimental 229

3 Results 229

3.1 AFM of fine-grain titanium 229

3.2 STM of fine-grain titanium 231

3.3 AFM/STM of TiN 232

3.4 Tunneling spectroscopy of TiO/TiN 233

4 Discussion 237

5 References 238

Summary. A survey of SPM (Scanning Probe Microscopy) methods on oxide-covered surfaces is given, regarding the role of preparation, examination techniques and conditions. STM and AFM measurements were carried out on oxide-covered titanium and TiN. Fine-grain titanium with lateral dimensions of 10-30 pm exhibited, after careful polishing, height differences of only a few nanometers at the grain boundaries. AFM pictures showed small substructures on these grains with xy dimensions of 20-50 nm and a z-range of 1-5 nm. The polishing process is discussed as a function of the (hkl) orientation of the grains. Stable STM pictures could not be recorded if the oxide films were prepared electrochemically in sulfuric acid. The modification of these oxide films with hydrogen, water, or nitrogen implantation is discussed. On nitrogen-implanted surfaces stable STM conditions were achieved. The reason for this behavior could be found in the voltage tunneling spectra: TiN exhibited a much better conductivity than normal Ti02.

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