Porvair plc, UK

Abstract

The growth of NanoCrystalline Diamond (NCD) films at very low substrate temperature on large area surface using a distributed antenna array (DAA) microwave reactor operating in H2/CH4/CO2 gas mixture is investigated. The estimated activation energy is in the range 1.3–3.2 kcal·mol− 1 depending on the injected microwave power and resulting substrate temperature range, which is comparable to values reported for other low-temperature NCD growth processes. The ability of the DAA reactor to deposit NCD films at a surface temperature down to 130 °C is demonstrated. NCD films composed of nanometric grains of 4.5 nm with a surface roughness of 27 nm are thus obtained, with a growth rate of 5 nm·h− 1. The decrease of the deposition temperature is followed by an increase of the renucleation rate leading to a reduction of the grain size and to a subsequent promotion of non-diamond phases. At this temperature, the decrease of the CH4 percentage in the feed gas permits to improve the film purity but leads to a drastic decrease of the growth rate down to 2.5 nm·h− 1. Finally, a successful attempt of NCD film deposition on polytetrafluoroethylene (PTFE) substrate is shown aiming at exploring the coating of temperature-sensitive polymeric substrates employed for biomedical applications.