|M.Sc Student||Tsach Yarden|
|Subject||The Contribution of Metallic Thin Films to the Nucleation|
and Growth Rate of Diamond Deposited in a HF-CVD
|Department||Department of Materials Science and Engineering||Supervisor||Research Professor E Dan Shechtman|
Chemical Vapor Deposition (CVD) diamond films were studied intensively in the last 30 years because of their superior mechanical, thermal, optical and electrical properties. The main obstacle to utilizing diamond films, as an engineering material is the long deposition time and the instability of the deposition procedure resulting in an expensive process. Yully Chuck, under the guidance of Prof. Alon Hoffman (Technion, Haifa 1997) found that the growth rate and nucleation density of diamond thin films improved significantly in the presence of titanium. In their study they surveyed the effect of different materials on the nucleation and growth of the Hot Filament CVD (HF-CVD) diamonds. Our present study is a continuation of the previous work. We aimed at quantifying the contribution of titanium to the nucleation and growth of the CVD diamond layers. We have developed a wedge shaped sputtered titanium substrate and studied the effect of the titanium layer thickness on the nucleation density and growth rate of the diamond film. The thickness of the titanium substrate produced in this manner changes linearly between 30 nanometers end zero. The diamond deposition was performed in a HF-CVD reactor. The effect of the titanium was compared to that of zirconium and hafnium, produced in the same manner. Our observations reveal that titanium has a unique, positive contribution to the nucleation and initial growth of the CVD diamond. A titanium substrate layer, 15 to 20 nanometers thick, was found to be the optimum for high diamond nucleation density, that reached up to 109 diamond particles per square centimeter. Zirconium and hafnium coatings, on the other hand, suppress diamond growth. Characterization of the titanium layer was carried on in a variety of methods: High-Resolution Scanning Electron Microscopy, Transmission Electron Microscopy, High-Resolution Transmission Electron Microscopy and Auger spectroscopy. No fundamental explanation was found to the unique contribution of the titanium.