Atomic hydrogen concentration mapping in thermal plasma chemical vapour deposition

Two-dimensional maps of atomic hydrogen concentration in reactive gas layers were measured using two-photon laser-induced fluorescence. The measurements were made in conditions of diamond-film chemical vapour deposition using a thermal inductively coupled plasma. Their purpose was to investigate the influence of the atomic hydrogen concentration in the reactive gas layer on the diamond growth. Concentration maps were obtained under parametric variation of the plasma flow conditions. Axial profiles were extracted from the measured maps and compared to temperature profiles measured by Rayleigh scattering to determine the degree of chemical non-equilibrium in the reactive layer. The non-uniform quenching over the measured area was accounted for with an iterative calculation of the species concentrations. For small differences of the atomic hydrogen concentration in the reactive layer a large variation in quality of the grown diamond was observed.