CVD diamonds for microelectronics and electronics of high powers

Properties of polycrystalline diamond wafers produced by chemical vapor deposition (CVD), important for microwave electronics are described. Diamond has a unique set of dielectric, thermal, chemical and mechanical properties, which are of primary interest for application in microwave electronics. The main ideas of CVD-technology are also presented. The dielectric properties in extremely broad frequency and the temperature range is (1 kHz-210 GHz, 70-800 K). The record breaking low values of dielectric loss tangent are observed (tan/spl delta//spl sim/3/spl middot/10/sup -6/ at T=300 K, f=170 GHz). However, they are about one order of magnitude higher than the theoretical lower loss limit for diamond. The data are compared with theory. The combinations of data on dielectric losses in broad frequency and temperature ranges give most information on the loss mechanisms. CVD diamond is considered currently as the most promising material for the windows of megawatt gyrotrons for microwave heating in fusion reactors.