Evaluation of Thermoelectric Conversion Performance of the Nitrogen-Containing Diamond Like Carbon Thin Films

This paper presents an investigation of the influence of nitrogen addition on the thermoelectric conversion performance of diamond-like carbon (DLC) films on glass substrates using RF plasma chemical vapor deposition. The respective thermoelectric conversion performances and Hall effect of the DLC films were evaluated and compared as a function of Nitrogen concentration. And film composition and atomic bond structure were characterized using Raman spectroscopy and XPS. At temperature of 473.2K, absolute value of Seebeck coefficients of the DLC films decreased concomitantly with increasing nitrogen concentration at 0—4.0at.%. However, the Seebeck coefficients of 4.0—8.1at.% were almost identical. At temperature at 298.2K, the Seebeck coefficients of 0—8.1at.% were almost identical regardless of the concentration of nitrogen. At temperature of 298.2K, specific resistance of the DLC films decreased concomitantly with increasing nitrogen concentration at 0—4.0at.%. However, the specific resistance of 4.0—8.1at.% was almost identical. The power factor of the DLC films increased concomitantly with increasing nitrogen concentration below the temperature of 398.2K. Hall effect measurements revealed that the difference by nitrogen concentration of Seebeck coefficient and specific resistance are expressed as a function of the carrier density and the carrier mobility respectively. Considering the results of Raman spectroscopy and XPS revealed that the sp3 bond in the DLC film increases with increasing nitrogen concentration. Thus, it was suggested that the electrical properties and semiconductor properties of DLC films depend on the sp2/sp3 fraction in the films.