A description of the experimental microwave discharge behavior versus pressure, power and reactor geometry for MPACVD diamond synthesis reactors

Recently two new microwave plasma-assisted chemical vapor deposition (MPACVD) diamond synthesis reactors [1,2] were designed, built and experimentally evaluated and their performance was compared to earlier MPACVD reactor designs [3]. In order to take advantage of the improved CVD diamond synthesis conditions that occur within the high pressure regime (160-300 Torr) the two reactors were designed to operate with high power densities and at high pressures. When these reactors operate at high pressures single crystal MPACVD diamond synthesis occurs over a large range of reactor conditions [1,2] such as: (1) pressure, p, 100->;300 Torr. (2) input power 1-6 kW, (3) flow rates, (4) methane to hydrogen concentrations of <; 1% to greater than 9%, (5) discharge power densities of 200-1000 W/cm³, (6) substrate holder design/geometry, (7) reactor design/geometry and (8) plasma/substrate position, Z_S.