Local crystallization and enhanced thermoelectric performance of glassy carbon induced by the electron beam irradiation

Glassy carbon can be used in a variety of harsh environments because it exhibits low electrical resistance, high thermal stability, chemically impermeability and hardness. In this work, we studied the potential application of the pyrolized glassy carbon as a thermoelectric material by electron beam irradiation. Irradiation with electron beam energy of 1.4 MeV and 0.2 MeV triggered local crystallization of glassy carbon, which was determined by a Raman spectroscopy. As the irradiation time was increased, the number of sp² hybridized carbons was gradually increased while the number of disordered carbons was decreased. This electron beam induced local crystallization caused a synergetic effect on a thermoelectric power factor of the studied glassy carbon films. Although the electrical conductivity was decreased by the e-beam irradiation, the Seebeck coefficient was significantly enhanced resulting in an improved power factor. The optimal power factor we obtained for the irradiated glassy carbon was ∼50% higher than that of the non-irradiated sample.