Deposition of carbon based materials by continuous and pulsed discharges

Abstract

This review surveys the recent developments in the plasma deposition of polycrystalline diamond (PCD) films from highly diluted (1%CH₄ in H₂) gas mixture and superhydrophobic fluorocarbon films from C₂F₄ gas. Specifically, the pulsed plasmas are also used and examined at different duty cycles and pulse periods. Emphasis is given to the role of pulsed plasmas with respect to continuous ones in controlling the gas surface interaction and the growth chemistry and in determining the material properties. The obtained materials have been characterised using a wide range of methods: scanning electron microscopy, atomic force microscopy, Raman spectroscopy, X-ray diffractometry, spectroscopic ellipsometry, water contact angle, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. Power modulation affects the PCD film morphology but deteriorates their optical and structural properties: the refractive index and the quality factor of continuous films are better than pulsed ones. As for fluorocarbon films, the control of both the plasma phase and the film deposited is improved under pulsed conditions. The pulsed plasmas, contrary to the continuous ones, allow to tune the CF₂ growth precursor and correspondingly the composition, structure and morphology of the film, exhibiting a superwater repellent surface with contact angles of up to 170°.

Keywords:

• Microwave CH₄–H₂ and radio frequency C₂F₄ discharges
• Continuous and pulsed plasmas
• Polycrystalline diamond and fluorocarbon films

Part of this work has been carried out in the frame of the ‘Progetto Strategico’ ATS PS_136 of Regione Puglia (Italy). The author is also grateful to Professor R. d’ Agostino and some of his group at the Chemistry Department, Bari University, for using some results of fluorocarbon films in the present review.