Interactions between hydrogenated diamond surface and adsorbates with different concentration of NO2 molecules: A first‐principles study

Abstract

To elucidate the effects of NO2 and H2O molecules on the surface conductivity of hydrogenated diamond film, models of various adsorbates containing different molecular ratio of NO2 and H2O on hydrogenated diamond (100) surfaces were constructed. The adsorption energies, equilibrium geometries of adsorbates, density of states, and atomic Mulliken populations were studied by using first‐principles method. The results showed that H2O molecule in the adsorbate could weaken the interactions between the adsorbates and hydrogenated diamond surface significantly. Compared with H2O molecule, NO2 molecule relaxes more dramatically when adsorbed on hydrogenated diamond surface. In addition, density of states for C(100):H–2NO2, C(100):H–NO2, and C(100):H–NO2 + H2O systems are very similar to each other, which indicates an obvious peak at valence band maximum level for all the three samples. It can be attributed to mainly single occupied molecule orbital of NO2 molecule and slightly C–H bond of C(100):H substrate. When the adsorbates contain one NO2 and two H2O molecules, the peak shifts slightly into valence band, but its intensity increases significantly. All the samples exhibit p‐type surface conductivity when adsorbed with pure NO2 molecules, and the surface conductivity remains as H2O molecules added into the NO2 adsorbate layer. However, for oxygenated diamond surface, very week interactions generate between diamond surface and various adsorbates. All the oxygenated diamond (100) surfaces with various adsorbates containing different NO2 and H2O molecules on it exhibit an insulating property.