AVS 50th International Symposium
    Plasma Science and Technology Tuesday Sessions
       Session PS+TF-TuM

Paper PS+TF-TuM4
Identification of the Growth Precursors for Hydrogenated Amorphous Carbon Growth

Tuesday, November 4, 2003, 9:20 am, Room 315

Session: Plasma Enchanced Chemical Vapor Deposition
Presenter: J. Benedikt, Eindhoven University of Technology, The Netherlands
Authors: J. Benedikt, Eindhoven University of Technology, The Netherlands
R.V. Woen, Eindhoven University of Technology, The Netherlands
M.C.M. van de Sanden, Eindhoven University of Technology, The Netherlands
Correspondent: Click to Email
The plasma chemistry and plasma composition of argon/acetylene expanding thermal plasma, used for fast (up to 70 nm/s) hydrogenated amorphous carbon (a-C:H) film deposition, was studied by means of Cavity Ring Down absorption Spectroscopy and Mass Spectrometry. Since the electron temperature in expanding thermal plasma beam is low (less than 0.3 eV) electron impact processes can be neglected and acetylene dissociation is argon ion induced. The C@sub 2@H radical was identified as the main growth precursor for hard (14 GPa) diamond-like a-C:H films. It was shown that under conditions where most of acetylene molecules are decomposed into C, CH and C@sub 2@ radicals, the a-C:H films are soft and polymer-like. Furthermore it was observed that good a-C:H films can be grown also under conditions when C@sub 4@H@sub 2@ molecules are the main plasma chemistry product and when reactive radicals as C@sub 2@H has already reacted away with acetylene in the gas phase. The mass spectrometry measurements of C@sub 4@H@sub 2@ molecule in the background of the plasma shows that C@sub 4@H@sub 2@ density depends on the wall condition (argon plasma activated or hydrogen plasma passivated) suggesting that C@sub 4@H@sub 2@ is one of the contributors to the film growth. C@sub 2@H and C@sub 4@H@sub 2@ as possible precursors for a-C:H growth is confirmed by recent Molecular Dynamics simulations which reveal reaction probabilities close to one for both species.