Review on the non-destructive characterization and application of doped and undoped polycrystalline diamond films
Übersicht über zerstörungsfreie Charakterisierung und Anwendungen von dotierten und undotierten polykristallinen Diamantfilmen
In this overview the mechanical, thermal and electrical properties of CVD (Chemical Vapor Deposition) diamond, determined by various non-destructive techniques, are highlighted and compared with calculations. In the case of Young's modulus the measurement results of high quality samples leads to an average value of 1126 GPa which is in good agreement with the calculated value of 1143 GPa and close to the Young's modulus of single crystalline diamond. However, values as low as 242 GPa were determined on 300 µm thick bulk CVD diamond. The differences in the measurement results can be traced back to extended voids in the sample. A traditional heated bar technique was used to measure the temperature dependent thermal conductivity of CVD-diamond. High quality polycrystalline diamond films reached a room temperature thermal conductivity of 20.5 W cm-1 K-1. This value is comparable to the thermal conductivity of the best single crystal diamonds available. For the lower quality samples, boundary scattering and point defects are most likely responsible for the lower thermal conductivity. The electrical properties of B-doped polycrystalline diamond films were characterized by temperature dependent Hall and conductivity measurements. These measurements together with a semi-empirical model give insight in to the current transport mechanism. The model indicates, that the electrical mobility in diamond thin films it lower compared with single crystal diamond. However, the current conduction mechanism are essentially the same when compared with single crystal diamond.