Nitrogen induced increase of growth rate in chemical vapor deposition of diamond

Polycrystalline diamond films have been grown by microwave assisted chemical vapor deposition from methane/hydrogen gas mixtures. The addition of small amounts of nitrogen with concentrations below 50 ppm to the process gas was found to drastically increase the deposition rate depending on the microwave power. At 4.2 kW microwave power a five times higher growth rate compared to nitrogen-free depositions was achieved. The optical transmission and thermal conductivity have been measured. The incorporation of small amounts of nitrogen does not degrade the infrared transmission of the samples; the thermal conductivity measured at room temperature decreased only slightly from 20.5 to 18 W/(cm K).