Influence of nitrogen–acetylene ratio on the optical and electrical properties of TiCN films for plasmonic applications

Titanium carbonitride (TiCN) films were fabricated by cathodic arc deposition on 1-µm-thick silicon dioxide/silicon wafers with various ratio of nitrogen (N2) and acetylene (C2H2) for alternative surface enhanced Raman scattering (SERS) sensors. The physical structure, chemical bonding, electrical properties and optical properties of the samples were systematically characterized. Electrical parameters, including carrier concentration and mobility, were calculated via optical and electrical techniques. The effect of nitrogen gas ratio (N/(C2H2 + N) (0.346 – 1.00) on plasmonic performance of nano-TiCN films was indicated by the quality factor and electron loss function. From Raman measurement, reducing the nitrogen gas ratio lowered Ti peak (~150 cm⁻¹) and phonon peak (605 cm⁻¹), while carbon-related peak intensity (1000 – 1800 cm⁻¹) increased. As nitrogen gas ratio decreased, carbon composition increased while the quality factors lowered. In addition, the direct optical band gap and electron loss function also turned red shift when the nitrogen gas ratio decreased. The nitrogen ratio 1.00 provided high quality factor and highest electron loss function peak. In summary, TiCN demonstrated as a plasmonic material for SERS sensors. It provided good electron transport parameters e.g. high carrier concentration on order of 1022 cm-3 and very low carrier mobility which observed through both optical and electrical characterization techniques.