Diamond deposition using a novel microwave applicator

This paper describes a novel microwave applicator that has the potential to allow microwave deposition of diamond films inside a metallic cylinder with an internal diameter of more than 10 cm.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 gasses, and a plasma jet is formed. The antenna and quartz housing are so arranged that the plasma jet emerges perpendicular to the antenna axis. This allows the jet to be directed towards the internal surface of a cylinder with diameter >50 mm.Diamond films have growth rates of up to 0.2–1 μm/h and exhibit a sharp Raman peak at 1332 cm⁻¹. Film growth is examined under a range of conditions including applicator–substrate distance, microwave power, surface temperature and chamber pressure.