Did you test other diamond substrates with different dopant levels, and were different results obtained?
Many different diamond substrates with different levels of n-type dopants were tested. All produced the same basic result. Depending on the resistance of the diamond substrate the slope of the IV-curve (open data points in Fig. 3.14) changed, as expected. Furthermore the distance between the diamond and the anode above which the phase could not be sustained, increased with increasing dopant density. These results have not been published because they do not add to the understanding of the underlying science involved. For the record, the following suite of experiments were done: • (i) the dopant level was varied • (ii) both oxygen and nitrogen donors were used • (iii) different crystallographic faces were doped • (iv) different types of diamond were doped namely: natural type IIa, synthetic type Ib, synthetic single crystalline CVD surfaces, synthetic polycrystalline surfaces.
