Influence of Different Nitrogen Plasmas Exposures of H-Diamond (100) Surfaces on Ambient Oxygen Adsorption, Nitrogen Bonding, and Thermal Stability Studied by X-Ray Photoelectron Spectroscopy

Abstract

This study reports on the influence of nitrogen plasma exposure of H-diamond (100) on the adsorption of adventitious oxygen, nitrogen bonding, and thermal stability studied by X-ray photoelectron spectroscopy. The nitrogen-plasma exposures include microwave (MW) and radio frequency (RF) (at pressures: 3 × 10−2 (damaging) and 7 × 10−2 Torr (nondamaging)) nitrogen plasmas. The largest amount of oxygen ambient adsorption occurs on the damaging RF(N2) (O = 2.8 at%) exposed surface, whereas for MW(N2) (O = 0.8 at%) and nondamaging RF(N2) (O = 1.3 at%) exposed surfaces, a lower oxygen concentration is observed. Also, the highest level of structural damage to the upper atomic layers of the diamond is induced by exposure to the damaging RF(N2), followed by nondamaging RF(N2) and MW(N2). Thus, the near-surface damage induced by the plasma interaction promotes adventitious oxygen adsorption (in various bonding configurations, including COx and C–NOx). For ambient-exposed MW(N2)-processed surface, nitrogen is adsorbed mainly in C–N/C=N state. Whereas for ambient-exposed nondamaging- and damaging RF(N2)-treated surfaces, nitrogen is bonded in mixed C–N/C=N and C≡N states alongside a small C–NOx component depending on the degree of surface defects. The damaging RF(N2)-exposed surface exhibits a lower oxygen and nitrogen thermal stability than the other cases.