Photoemission spectroscopy was used to compare the effects of a hydrogen or argon plasma on natural‐type 2B diamond (111) surfaces, while the diamond was heated to 350 °C. After the hydrogen plasma the surface exhibits a negative electron affinity, indicative of a hydrogen‐terminated surface. In contrast, the argon plasma was found to result in a surface with a positive electron affinity of 1.0 eV, indicating the removal of hydrogen from the surface. Features characteristic of graphite were not observed. After reexposing the surface to a hydrogen plasma, the spectrum was identical to the spectrum obtained after the initial hydrogen plasma.