Bonding, structural properties and thermal stability of low damage RF (N2) plasma treated diamond (100) surfaces studied by XPS, LEED, and TPD

Abstract

In this work, we investigate the interaction of N2 radio frequency (RF) plasma with single crystal diamond (100) surface. This study shows that a low-level damaged nitrogen terminated diamond (100) surface may be produced using a bent plasma source and a grounded mesh electrode placed at the source exit. Optical emission spectroscopy (OES) was used to characterize the species present in the plasma. The chemical, structural and thermal stability of the N-terminated diamond (100) surface were investigated in-situ by X-ray photoelectron spectroscopy (XPS), temperature programmed desorption (TPD) and low energy electron diffraction (LEED). OES showed that increasing the flow rate and operating pressure could decrease the ratio of charged-to-neutral nitrogen particles. From XPS results it is determined that the adsorbed nitrogen to the diamond surface may occupy a number of bonding configurations and that the damage to the surface upon nitridation, as reflected in the C(1s) peak shape analysis, can be minimized. From annealing experiments, it was found that some of the incorporated nitrogen onto the diamond surface is stable upon annealing to 1000 °C. LEED results show that upon a short RF (N2) plasma exposure time a (1 × 1) pattern was observed which was preserved upon annealing to 1000 °C suggesting that a thermally stable and ordered nitrogen terminated surface was formed. The TPD spectrum shows two low-temperature N2 desorption peaks that are associated to weakly bonded nitrogen chemisorbed species to the diamond surface at 210 and 560 °C.