We review the measurements of transient capacitance and junction impedance, as well as identifications of charge transport mechanisms, made in polycrystalline diamond films by several researchers, in their efforts to analyse the nature of electronically active defects. Despite the different sources of their samples, there are similarities in the behaviour of many polycrystalline diamond films and also of single crystal diamond. However, only some bandgap energy levels have been identified, the most dependable being those due to boron. The changes caused in the electrical properties of diamond films by thermal annealing and hydrogenation are also examined. Although it seems that grain boundaries, rather than compensation, may dominate the electrical properties of lightly doped polycrystalline samples, the compensation effect has been discussed and examined in the light of their single crystal counterparts, and because it is a significant factor in heavily doped films.
- Diamond firms
- Electrical conductivity