Surface plasmon resonance and electrical properties of RF: magnetron sputtered carbon–nickel composite films at different annealing temperatures

In this work, the optical absorption spectra of carbon–nickel films annealed at different temperatures (300–1000 °C) with a special emphasis on the surface plasmon resonance (SPR) were investigated. The films were grown on quartz substrates by radio-frequency (RF) magnetron co-sputtering at room temperature with a deposition time of 600 s. The optical absorption peaks due to the SPR of Ni particle are observed in the wavelength range of 300–330 nm. With annealing temperature increasing up to 500 °C due to the increase in Ni particle size, the intensity of the SPR peaks increases, but weakens with annealing temperature increasing over 500 °C. The Ni nanoparticle size, the dielectric function of carbon matrix (ε _m) and the plasma frequency of the free electrons (ω _p) at 500 °C have the maximum values of 21.63 nm, 0.471 and 5.26 × 10¹⁵ s⁻¹, respectively. The absorption peak shows a redshift trend up to 500 °C and then turn to blueshift with annealing temperature increasing over 500 °C. These observations are in a good agreement with the electrical measurements in temperature range of 15–520 K and the Maxwell–Garnett (M–G) effective medium theory (EMT).