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To meet various application requirements, it is important to enable an improvement of a-C structure and properties, such as hardness, adhesion, and wear resistance. In this study, we used the Raman spectroscopy to investigate the a-C thin films structure dependence on the different deposition parameters. The effect of nitrogen, argon, and hydrogen gas flow rate was analyzed to determine the influence on the film properties. The change in the gas type, combination, and flow had a significant influence on the D and G bands of the a-C Raman spectra. The addition of N2into the chamber promoted the sp2creation, while with adding hydrogen the layer contained more sp3bonds. The depositions of a-C thin films were carried out in pulsed arc discharge vacuum installation. Micro-Raman measurements of the deposited materials were performed using an ISA Dilor-Jobin Yvon-Spex Labram confocal system with 632.8 nm radiation from a He-Ne laser using a back-scattering geometry.

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The impact of different doping levels of boron-doped diamond on the surface functionalization was investigated by means of electrochemical reduction of aryldiazonium salts. The grafting efficiency of 4-nitrophenyl groups increased with the boron levels (B/C ratio from 0 to 20,000 ppm). Controlled grafting of nitrophenyldiazonium was used to adjust the amount of immobilized single-stranded DNA strands at the surface and further on the hybridization yield in dependence on the boron doping level. The grafted nitro functions were electrochemically reduced to the amine moieties. Subsequent functionalization with a succinic acid introduced carboxyl groups for subsequent binding of an amino-terminated DNA probe. DNA hybridization significantly depends on the probe density which is in turn dependent on the boron doping level. The proposed approach opens new insights for the design and control of doped diamond surface functionalization for the construction of DNA hybridization assays.

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