Influence of the electron cyclotron resonance microwave plasma on growth and properties of diamond-like carbon films deposited onto r.f. biased substrates

Abstract

Growth of diamond-like carbon (DLC) thin films on r.f. (13.56 MHz) biased substrates was modified by application of microwave (2.4 GHz) electron cyclotron resonance (ECR) plasma. Microhardness measurements, ellipsometry, optical absorption measurements, electrical conductivity measurements and Raman spectroscopy were used for complex characterization of the prepared DLC films. Application of the microwave ECR plasma resulted in an increase in the microhardness and index of refraction of the prepared films, probably via densification enhanced by more intensive ion bombardment. The film deposition rate remained practically unchanged, provided the absorbed microwave power was lower than a certain threshold value. The deposition rate, however, decreased, if the threshold value was exceeded. The optical band gap and the electrical conductivity of the films were influenced by the substrate bias during film deposition, but they were insensitive to the absorbed microwave power. IR absorption spectra demonstrated the prevalent content of sp 3 carbon and only a small fraction of sp 2 carbon bonds in the prepared films. Raman spectra exhibited features characteristic of DLC films.