IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Thin Films Friday Sessions
       Session TF-FrM

Paper TF-FrM2
Probing Surface Species on a Diamond C(111) Surface During the Chemical Vapour Deposition of Diamond

Friday, November 2, 2001, 8:40 am, Room 123

Session: Diamond and Related Materials
Presenter: M. Buck, University of St Andrews, Scotland
Authors: A. Heerwagen, University of Heidelberg, Germany
M.T. Strobel, University of Heidelberg, Germany
M. Himmelhaus, University of Heidelberg, Germany
M. Buck, University of St Andrews, Scotland
Correspondent: Click to Email
The bottleneck in the accurate modeling of the diamond growth by chemical vapour deposition (CVD) is the lack of knowledge of the surface species and chemistry. In contrast to the gas phase, there is a deficit in experiment data for chemical species and reactions associated with the surface of a growing diamond film. The reason for this striking imbalance between experimental data on the gas phase and the surface lies in the diffculty to probe surface species in situ under the conditions of diamond CVD. Under these conditions, which are prohibitive for other surface science techniques we have applied IR-visible sum frequency generation (SFG) to probe the surface of a natural diamond during the CVD process, using a hot filament (HF) reactor and a gas mixture of hydrogen and methane. Monitoring the range of the C-H stretching vibrations, a single band reflecting a monohydrogen termination of the diamond substrate surface is observed under conditions which yield high quality diamond films. A decrease of the filament temperature from 2000°C to 1850°C leads to a decrease in intensity of this peak appearing around 2820 cm-1. At filament temperatures below 1800°C a new band at 2809 cm-1 emerges while the peak at 2820 cm-1 vanishes. Lowering the substrate temperature has a minor influence on this spectral feature but, instead, a new band at 2855 cm-1 appears. Changing the composition of the gas phase causes the intensity and frequency of the monohydrogen band to vary significantly. In particular, in a pure hydrogen atmosphere it blue-shifts to 2830 cm-1 while a pronounced increase in intensity is detected. Comparison of these results with previous SFG data obtained under ultra high vacuum reveals pronounced similarities. Furthermore, the identification of the species and surface structure associated with the peak at 2855 cm-1 seems to be vital for improving the quality of CVD diamond films grown at lower temperatures.