Hard-hydrogenated tetrahedral amorphous carbon films by distributed electron cyclotron resonance plasma

Abstract

Hard-hydrogenated tetrahedral amorphous carbon films (ta-C:H) are deposited from acetylene-fed distributed electron cyclotron resonance (DECR) plasma over large area (300 mm diameter disk) at near room temperature (below 140 °C). The effects of the ion flux and energy on the structure and physical properties are investigated. For a constant substrate bias V 0 of −150 V, the mass–density, Young’s modulus and hardness reach a maximum value of ∼2.5 g/cm 3, ∼280 GPa, and ∼45 GPa, respectively, and the hydrogen content reaches a minimum of 26 at.% at the maximum ion flux ϕ + of ∼6.3 × 10 15 ions cm −2 s −1. For a constant ion flux and pressure, the mass–density and Young’s modulus reach a maximum at a substrate bias of −300 V, and the hydrogen content is minimised. Electron diffraction, and Raman spectra show that the films grown at the maximum ion flux and a negative substrate bias ranging between 150 and 500 V are ta-C:H. The films contain sp 2-carbon clusters and chains. sp 2-carbon clustering increases with the increase of the substrate bias and decreases with the increase of the ion flux. The disorder increases with the ion flux and decreases with the bias. The optical band-gap decreases with disorder and with sp 2-carbon clustering. It depends primarily on disorder rather than on clustering.