AFM and XPS studies of a homoepitaxial diamond (001) surface nitrided using 500-eV N₂⁺ ion beam

A homoepitaxially grown p-type diamond (001) surface was nitrided by irradiation with a 500-eV N₂⁺ ion beam. X-Ray photoelectron spectra (XPS) were taken in situ during the nitridation. The C1s and N1s XPS spectra were divided into three (A, ~ 284.7; B, ~ 285.6; and C, ~ 287.3 eV) and four (D, ~ 398.4; E, ~ 399.5; F, ~ 401.0; and G, ~ 1403.3 eV) components, respectively. The A component of the C1s core level originated from the diamond substrate lying under the nitrogen penetration zone. The B and C components came from the nitrogen-diluted layer and from the carbon nitrides, respectively. The composition ratio of nitrogen/carbon in the C phase, N_D+F/C_C, was 0.71. The N_all/C_B+C ratio was 0.25. The morphology of the surface was also measured in air by atomic force microscope (AFM). It was found that grain-like material covered the surface after nitridation. A typical grain size was approximately 50 nm in diameter with a height of 5 nm. However, the grains themselves were not carbon nitrides. The crystallinity of the nitride was investigated using reflection high-energy electron diffraction (RHEED), but the formation of β-C₃N₄ could not be confirmed from the RHEED patterns, due to overlapping with the twin structures of diamond.