Influence of the Nitrogen-Containing to Thermoelectric Performance of Diamond Like Carbon Thin Films

Abstract

This paper presents an investigation of the influence of nitrogen addition on the thermoelectric performance of diamond-like carbon (DLC) films on glass substrates using RF plasma chemical vapor diposition (CVD). The DLC films were prepared using methane (CH₄) with 0—40% nitrogen (N₂) concentrations as the source gas. The respective thermoelectric performances of the DLC films were evaluated and compared. The Seebeck coefficients of the DLC films decreased concomitantly with increasing nitrogen concentration at 0—20%. However, the Seebeck coefficients of 20% and the 40% were almost identical. The specific resistance of the DLC films decreased concomitantly with increasing nitrogen concentration at temperatures of room temperature to 150°C; above that temperature, the specific resistance of each DLC film was identical. The specific resistance decreases significantly with increasing nitrogen content, but the Seebeck coefficient decreases only slightly. The power factor (PF) of the DLC films increased concomitantly with increased nitrogen concentration below the temperature of 125°C. Results show that the PF quality of DLC films was affected strongly by the magnitude of the specific resistance. Hall effect measurements revealed a decreased specific resistance of the DLC films because of increased carrier concentration attributable to increased N₂ contents. Raman spectroscopy measurements suggest that structural changes in the films influenced the DLC films' thermoelectric performance.