Amination of diamond film by ammonia microwave plasma treatment

•The deposition and amination of diamond film were carried out in the same MPCVD system.•Microwave-excited ammonia plasma treatment is demonstrated as an effective method to aminate diamond surface.•The modification mechanism was discussed briefly and verified by theory analysis and OES study.

Functionalization of diamond films is important for various applications, such as electrochemical sensors. In this study, high quality diamond films were prepared by microwave plasma chemical vapor deposition (MPCVD). These surfaces were then functionalized by a surface amination modification (ammonia plasma) using the same system. The characterization results demonstrated that both the surface morphology and microstructure of the diamond films were not altered by the ammonia plasma treatment. The surface nitrogen content was assessed by XPS analyses, which revealed that amine groups (− NH2) were generated on the diamond film surface efficiently. The − NH2 concentration on modified diamond film surface was equal to 6.71% (denoted as − NH2/100C). The contact angle of water was decreased as the hydrophilicity of the aminated diamond film was increased. Based on the optical emission spectrum (OES) study, NH and NH2 radicals were generated in the microwave plasma, and are regarded as the crucial precursors for creating the amine group on diamond surface.