Characterization of chlorinated chemical vapor deposited and natural (100) diamond

The chemistry of chlorine interacting with chemical-vapor deposited (CVD) diamond films and natural C(100) diamond has been investigated. High resolution electron energy loss spectroscopy of polycrystalline CVD diamond reveals a strong band at 2900 cm(-1), with two maxima and a broad shoulder on the energy loss tail. The two maxima represent monohydride stretches on {111} and {100} crystal facets, while the broad shoulder is attributed to olefinic stretches associated with defects on {111} surfaces. Reacting the CVD surface with atomic chlorine removes all monohydride vibrational structure except that associated with {111} defects, whose intensity remains unchanged. Only a small feature at 800 cm(-1) is evident as a possible C-Cl stretch. Auger spectroscopy confirms the presence of chemisorbed chlorine on both C(100) and CVD diamond and reveals a strong preference for chlorine addition to {100} facets. The only chlorine containing species observed by secondary ion mass spectrometry on natural or polycrystalline diamond is C2H4Cl+. This ion is believed to originate from the same surface species regardless of the sample under study. We suggest that chlorine preferentially adsorbs to {100} surfaces by substituting for surface hydrogen, whereas sp(2) hydrogen-terminated defects appear to be unreactive to chlorine substitution. (C) 1999 Elsevier Science B.V. All rights reserved.