Transport of and deposition from hydrocarbon radicals in a flow tube downstream from a CH4 RF discharge

The stream technique is used for the measurement of the surface loss probability (β) and sticking coefficient (s) of a hydrocarbon radical. A CH4 RF inductive coupled discharge is used as source of CHi radicals and H atoms. These species lead to film formation in the downstream region of the tube. The thickness profiles along tube of the deposited carbon films are measured. The areal density and the structure of the carbon deposits on Si wafers, which are mounted inside tube, are studied by EPMA and RHEED. At 300 K the deposition profile of the a-C:H films can be approximated by exp(−x/L), where x is the position in the tube and L is the transport length. By measuring L, β coefficients can be determined. On the basis of a comparison with literature, one can conclude that methyl radicals contribute predominantly to a-C:H deposition.