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Keywords:

  • activation energy;
  • growth kinetics;
  • linear antenna microwave CVD;
  • low temperature;
  • polycrystalline diamond films

Abstract

Recently, there is a great effort to increase the deposition area and decrease the process temperature for diamond growth which will enlarge its applications including use of temperature sensitive substrates. In this work, we report on the large area (20 × 30 cm2) and low temperature (250 °C) polycrystalline diamond growth by pulsed linear antenna microwave plasma system. The influence of substrate temperature varied from 250 to 680 °C, as controlled by the table heater and/or by microwave power, is studied. It was found that the growth rate, film morphology and diamond to non-diamond phases (sp3/sp2 carbon bonds) are influenced by the growth temperature, as confirmed by SEM and Raman measurements. The surface chemistry and growth processes were studied in terms of activation energies (Ea) calculated from Arrhenius plots. The activation energies of growth processes were very low (1.7 and 7.8 kcal mol−1) indicating an energetically favourable growth process from the CO2[BOND]CH4[BOND]H2 gas mixture. In addition, from activation energies two different growth regimes were observed at low and high temperatures, indicating different growth mechanism.