CHARACTERIZATION OF CVD DIAMOND FILMS BY NUCLEAR TECHNIQUES WITH ALPHA-PARTICLES

Alpha particles were used for the first time to characterize the trans port properties of polycrystalline CVD diamond films. The advantages w ith respect to other techniques which make use of beta particles or li ght are that it is easier to discriminate between holes and electrons, and localization of deposited energy is more precise because alpha pa rticles do not suffer from energy loss fluctuations and straggling. Th e results indicate that, on average, the transport properties of elect rons and holes in CVD diamond are roughly the same and that lifetimes are in the range 0.3-1 ns. The broad distribution of collected energie s is indicative of strong inhomogeneities in the transport of electron s and holes which are assumed to be related to the presence of crystal line grains of different dimensions. The values quoted in the literatu re for average carrier collection lengths, and obtained using minimum ionizing particles, are likely to be ascribed to charge transport in g rains of dimensions in the range 10-100 mu m.