Effect of argon addition on the growth of thick single crystal diamond by high-power plasma CVD

Diamond films were synthesized with up to 50% argon in the gas phase using high power plasma‐assisted chemical vapour deposition (PACVD). This resulted in a strong increase of the deposition rates. Polycrystalline diamond (PCD) films grown with Ar have shown a higher incorporation of sp2 phases but with no dramatic change in crystal morphologies. Thick single crystal diamond films did not show any obvious change in crystal quality though. By using optical emission spectroscopy (OES) and plasma simulation, it was found that the gas temperature is increased by the addition of argon by at least 500 K. This in turn promotes dissociation of H2 into H‐atom as would be obtained from an increase of the plasma power density. High‐power PACVD with argon addition is thus an efficient technique for the fast growth of thick single crystal films without the cost and additional problems related to an increase of the injected microwave power.