Microwave plasma reactor design for high pressure and high power density diamond synthesis

The design and performance of an improved microwave plasma assisted chemical vapor deposition (MPACVD) reactor is described. This reactor operates with high power densities and at pressures up to 300 torr. Differences from earlier MPACVD reactor designs [4] include an increase in applicator and dome size and the excitation of the applicator with a new hybrid TM0/TEM001 mode. The reactor is experimentally evaluated by synthesizing single crystal diamond (SCD) at pressures from 180 to 300 torr with absorbed power densities between 400 and 1000 W/cm(3). Without N-2 addition SCD growth rates as high as 75 mu m/h were observed. A SCD growth window between 950 degrees C and 1300 degrees C was identified and within this growth window growth rates were 1.2 to 2.5 times greater than the corresponding growth rates for earlier reactor designs. SCD characterization by micro-Raman spectroscopy, SIMS, and by IR-UV transmission spectroscopy indicated that the synthesized SCD quality is that of type IIa diamond. (C) 2012 Elsevier B.V. All rights reserved.