Impact of energy density and stress fields on the nucleation dynamics of plasma deposited a-C:H films A. Golanski a, * , J.P. Stoquert a , P. Kern a , F. Piazza a,b , S. Schulze c a Centre National de la Recherche Scientifique (CNRS), Laboratoire ‘‘PHASE’’, 23, rue du Loess, F-67037 Strasbourg, France b Department of Engineering, University of Cambridge, CB2 1PZ Cambridge, UK c Institut f€ ur Physik, Technische Universit€ at Chemnitz, 09107 Chemnitz, Germany Abstract A distributed electron cyclotron resonance plasma reactor powered by a microwave generator operating at 2.45 GHz was used to deposit a-C:H films at room temperature on RF biased (100) silicon substrates. Modifying the substrate bias, the ion dose rate and the composition of the precursor gas enabled the average deposited energy density to be varied. For the pure acetylene plasma and under constant substrate bias an increasing ion dose-rate leads to an in- creased sp 3 hybridized C fraction. The effect is correlated to propagation and overlap of the hypersonic shock waves generated by high energy density collision cascades. The corresponding timescale is within the picosecond range. The shock wave related effects are enhanced when argon is added to the acetylene plasma. Once the collision cascades and shock wave comes to rest, the subsequent nucleation of the sp 3 hybridized component is enhanced by the tensile stress- mediated nucleation process. Ó 2003 Elsevier Science B.V. All rights reserved. PACS: 81.05.Uw; 52.77.Dq; 68.55.)a; 68.55.Ac Keywords: Carbon; Plasma; Deposition; Nucleation; Hybridization; Shock-waves 1. Introduction Although physical properties of plasma-grown amorphous hydrogenated carbon (a-C:H) films may be regarded as unambiguously correlated to the process parameters, the impact of the energy density deposited by energetic ions on the a-C:H morphology is not completely understood. In the plasma deposition process the relative amount of sp 2 hybridized C, sp 3 hybridized C, and hydrogen depends on the ion energy and the plasma pa- rameters [1]. Within the ion energy range char- acteristic of the plasma immersion processing (between 10 and 600 eV) the mean free path of displaced atoms is close to the interatomic dis- tances in the solid. Under such conditions the energy transport processes can be associated with shock wave propagation [2,3]. The goal of the present work is to shed more light on the influ- ence of the shock wave mechanism on the nucle- ation process and microstructure of the a-C:H thin films. * Corresponding author. Tel.: +33-388-10-6250/6253; fax: +1-33-388-10-6253/6293. E-mail address: andre.golanski@phase.c-strasbourg.fr (A. Golanski). 0168-583X/03/$ - see front matter Ó 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0168-583X(03)00873-5 Nuclear Instruments and Methods in Physics Research B 206 (2003) 731–735 www.elsevier.com/locate/nimb