A NEUTRON AND X-RAY-DIFFRACTION STUDY OF THE INFLUENCE OF DEPOSITION CONDITIONS ON THE STRUCTURE OF A-C-H

The atomic scale structure of amorphous hydrogenated carbon (a-C:H) fi lms prepared from an acetylene precursor by plasma enhanced chemical v apour deposition (PECVD) and a fast-atom source (FAS) have been studie d by neutron and X-ray diffraction. The effect of beam energy on the s tructure of the film is investigated, and comparison is made to sample s prepared using at fast atom (neutral particle) source, also using ac etylene as the precursor, The results show that, in both deposition me thods, increasing the beam energy produces a lower total sp(2) hybridi sed carbon content in the film with evidence for a shift from pure ole finic to some aromatic/graphitic bonding in the FAS samples. The high resolution real-space neutron diffraction data allows a direct determi nation of the single:double bond ratio, and also shows the presence of sp(1) hybridised carbon bonding environments.