AVS 45th International Symposium
    Surface Science Division Wednesday Sessions
       Session SS2-WeA

Paper SS2-WeA9
Adsorption and Reaction of Chlorine on Low Index Diamond Single Crystal Surfaces

Wednesday, November 4, 1998, 4:40 pm, Room 309

Session: Photochemistry and Deposition
Presenter: S. Hadenfeldt, University of Hamburg, Germany
Authors: S. Hadenfeldt, University of Hamburg, Germany
C. Benndorf, University of Hamburg, Germany
Correspondent: Click to Email
The lowering of the substrate temperature achieved by the low pressure diamond deposition from halogenated precursors is believed to involve surface processes, including halogen adsorption, desorption and reaction with H(ad). In this work we studied the adsorption of chlorine on the low index diamond (100), (111) and (110) single crystal surfaces as well as on polycrystalline diamond CVD films in UHV using thermal desorption spectroscopy (TDS), Augerelectron spectroscopy (AES), low energy electron diffraction (LEED) and photoelectron spectroscopy (UPS / XPS). Elemental halogen was dosed by solid state electrolysis of silverchloride at elevated temperatures or direct dosing of chlorine gas through a heated oxide ceramics tube. The single crystals were regularely cleaned by pretreatment in a hydrogen plasma and showed clear reflexes in LEED. The CVD films were studied as received from the CVD process. In AES upon successive halogen dosing a linear increase of the intensity of the halogen Auger signal and a simultaneous decrease in intensity of the 272 eV carbon signal can be seen at first. No LEED overstructures could be observed upon adsorption on either surface. Depending on the sample preparation and history, in general two different desorption behaviours are observed in TDS. From the hydrogen rich, plasma prepared surface chlorine is desorbed continuously with a maximum around 600 K. Around 850 K chlorine is completely removed. On a hydrogen depleted surface, where less halogen adsorbs at a given exposure, two regions of chlorine desorption can be observed. Up to 730 K a steady decrease of chlorine is noted, which levels off, until finally all chlorine is desorbed around 950 K. Halogen uptake of the diamond surface can be increased either by thermally activating the surface or by dosing of atomic hydrogen prior to halogen adsorption.