Thermal resistance of thin diamond films deposited at low temperatures

Abstract

The thermal resistance for conduction normal to diamond layers only a few microns thick, deposited at temperatures of about 500 °C on silicon using microwave-plasma-assisted chemical vapor deposition (MPACVD) and electron cyclotron resonance enhanced MPACVD, is measured using a specific laser-heating method. A detailed analysis of the results obtained using this method allows the determination of the effective diamond–silicon boundary resistance and the resistance within the diamond layer independently of one another. The analysis shows that the effective boundary resistance is comparable to or even larger than the resistance within the thin diamond layers, and suggests that it depends on the grain dimensions at the interface. For grain sizes of 10 nm, an average effective boundary resistance of 2.4×10−7 m2 K/W is determined, whereas at 1.2×10−8 m2 K/W it is significantly lower for grains about an order of magnitude larger. The resistance within the diamond shows a similar qualitative behavior with respect to grain size.