Electrical properties and Raman characterization of a-C thin films deposited by thermal CVD

Amorphous carbon (a-C) thin films deposited with thermal CVD, have been characterized by a standard two-probe method using Advantest R6243 DC Voltage Current Source/Monitor and SemiPro Curve Software and Raman scattering experiment at an excitation wavelength of 514.5 nm provided by HORIBA Jobin Yvon (HR800) Raman. The films were prepared at various deposition temperatures ranging from 650-900°C. The conductivity of a-C thin films increased proportionally with the deposition temperature and the film deposited at 750°C shows large photoconductivity. I_D/I_G ratio of Raman spectra increased relatively with the deposition temperature as an indication of the disorderliness of a-C thin films. This is supported by the optical properties measurement whereby the optical band gap decreased from 0.65 to ~0.0eV due to the increase of sp² bonded carbon configuration.