Structural and functional characterization of HPHT diamond crystals used in photoconductive devices

Diamond films are extensively studied for applications as functional materi al for UV photoconductors. CVD-grown polycrystalline diamond films show ver y interesting performances, but their complete exploitation is actually lim ited by a slow time response if compared to other materials, by a relativel y high concentration of structural defects, impurities and grain boundaries , which may affect the collection length of photogenerated charges. High-qu ality single crystal diamonds could solve some of these problems. The absen ce of grain boundaries can produce longer collection lengths. The nitrogen and impurity contents can be reduced and then large type-IIa diamond single -crystals can be obtained. In this work, a detailed structural and function al characterization of type Tb HPHT diamond crystals has been carried out a nd the results have been compared to similar characterizations of CVD films to evaluate the different behavior, taking also into account that these hi gh pressure high temperature (HPHT) diamond crystals contain several tens p pm of nitrogen.