Not only the electrical properties of diamond, but also it's thermal properties make it an interesting material for industrial applications in the semiconductor industry. At room temperature the heat conductivity of diamond is about 20-25 W/cmK making it approximately 4-5 times larger than that of copper or ß-SiC and approximately 15 times larger than that of silicon. The maximum value of 50-60 W/cmK is reached at temperatures of about 80°K. The thermal expansion coefficient of 1.1 x 10-6 at room temperature is almost linear with respect to temperature and is therefore comparable with that of silicon and Invar (65% Fe + 35% Ni). The high thermal conductivity and low electrical conductivity of diamond make it possible to use diamond as a heat sink in electrically high powered devices. In addition, the high thermal conductivity of diamond combined with it's high optical transparency make it possible to use diamond as a window material for high powered lasers or for other intense radiation sources.