The exchange of radio-frequency plasma-excited atomic O with chemisorbed D, and vice versa, on single crystalline diamond (100) 2 × 1 has been investigated by elastic recoil detection analysis (ERDA), Rutherford backscattering spectrometry (RBS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS). It was found that the O-D, as well as D-O, exchange processes were thermally activated by the diamond substrate. The surface D was only partially exchanged by atomic O at room temperature. At elevated temperatures, the replacement of D by O was greatly enhanced, with 80% substitution by O at 300°C. It was also observed that the uptake of O proceeded more readily on the pre-deuterated surface compared to the clean surface. Ultra-shallow depth profiling revealed that atomic beam treatment of single crystalline samples at 800°C resulted in only superficial uptake of D and O, with no surface incorporation within the shallow analysis depth. The replacement of pre-adsorbed O by RF-excited atomic D was also studied by TOF-SIMS. Pre-adsorbed O was relatively stable and resisted removal at 300°C. D dosed onto the oxygenated surface was found to co-adsorb with O, possibly as surface bound OD species. Mechanisms for the O-D and D-O exchange processes were discussed in connection with the atomic structure of the C(100) surface. © 2002 Elsevier Science B.V. All rights reserved.