NH_2 and NH Surface Production in Pulsed NH_3 Plasmas on TiO_2: A Steady-State Probe of Short Pulse Plasmas

摘要

Understanding the gas-phase and surface chemistry of NH_x species in pulsed NH_3 plasmas can lead to optimized plasma conditions for nitriding metal oxide surfaces such as TiO_2. Gas-phase densities and surface reactions of NH and NH_2 in pulsed NH_3 plasmas used to nitride TiO_2 surfaces were explored by systematically varying peak plasma power and pulsing duty cycle. Results from laser induced fluorescence and optical emission spectroscopy studies reveal interconnected trends of gas-phase densities and surface reactions. Divergent trends in NH, NH_2 H_α, H_γ, N_2~+, and N densities found in short pulse plasmas are explained by plasma pulse initiation and afterglow effects. NH_2 and NH surface scatter coefficients were measured with the imaging of radicals interacting with surfaces technique as a function of plasma parameters, including pulse sequence. Results show NH_x species primarily scatter off of TiO_2 and are correlated to NH gas phase densities.