Diamond deposition using a novel microwave applicator

This paper describes a novel microwave applicator that has been used to deposit diamond films from a hydrogen/methane/oxygen mixture onto silicon substrates. The design consists of a coaxial antenna that passes perpendicularly through a rectangular waveguide and forms a plasma inside a vacuum chamber. A quartz envelope around the antenna feeds reactant gases along its axis to the antenna opening. Here the microwave field (2.45 GHz) is generated in the reactant gases and a plasma jet is formed. As the plasma is in the form of a jet, irregularly shaped objects may be coated in the plasma without disturbing the microwave field to the extent observed in resonant field systems. Diamond films have growth rates of up to 0.5 μm/h and exhibit a Raman peak (excitation source HeNe laser at 632 nm) at 1332 cm−1. Film growth is examined under a range of conditions including applicator–substrate distance, microwave power and chamber pressure.