Dielectric properties of single crystal diamond

Abstract

LCR measurements have been performed on type IIa and type Ib single crystal diamonds, in an attempt to identify any differences in their dielectric characteristics. It is found that the type IIa diamond, which contains little nitrogen, behaves as an ideal insulator, with the dielectric loss appearing to be frequency independent at low temperatures, whilst assuming a frequency dependence at high temperatures. In contrast, the type Ib diamond samples exhibited a dielectric loss peak in the temperature-dependent data, from which a thermal activated process with an Ea of 1.67 eV can be determined using a simple Debye law relationship. However, the data suggests that a dielectric relaxation constant (nitrogen-induced dipole) of 1017 Hz is evident in the Ib system, which is much higher than that predicted by the Debye model, as such it is unlikely due to the dipole moment itself. A possible physical mechanism responsible for this phenomena is simply the ionization of a nitrogen centre with a defect level lying at 1.7 eV below the conduction band.