Diamond-like carbon is a promising material for MEMS and opto-electronic systems applications. There is a notion that the hybridised sp³ (diamond-like) fraction controls the mechanical properties and the sp² fraction (graphite-like) determines the electro-optical properties. We investigated amorphous hydrogenated diamond-like carbon (a-C:H) films synthesised using an inductively coupled hydrocarbon plasma reactor under varying bias. The films were characterised using UV Raman, X-ray C_1s photoelectron, N-IR spectroscopy, scanning probe microscopy (SPM) and nano-indentation measurements. We found that all examined samples displayed essentially the same amount of the sp³ constituent, whereas the configuration of the sp² fraction was different. The sp² fraction of both aromatic rings and olefinic chains in examined films. We found that Tauc gap E_t, was controlled by the perturbation of the π tail states of the sp² fraction. The Tauc gap E_t, was determined by N-IR and surface conduction band E_oi, measured by SPM changed inversely with an increase of bias. Results obtained using nanoindentation measurements show that mechanical properties such as hardness and Young's modulus increased with an increase of bias for all films studied. These results indicate that mechanical properties of a-C:H films (hardness and Young's modulus) not only controlled by the amount of the sp³ bonding but also are determined by the degree of the sp² bonding arrangement.

Date Published: 29 December 2005
PDF: 9 pages
Proc. SPIE 6035, Microelectronics: Design, Technology, and Packaging II, 603503 (29 December 2005); doi: 10.1117/12.638712

Published in SPIE Proceedings Vol. 6035:
Microelectronics: Design, Technology, and Packaging II
Alex J. Hariz, Editor(s)