Influence of temperature on the hydrogenated amorphous carbon films prepared by plasma-enhanced chemical vapor deposition

Abstract

Hydrogenated amorphous carbon (a-C:H) films were deposited in a plasma-enhanced chemical vapor deposition (PECVD) system. The substrate temperature at deposition was found to have significant effects on the film stoichiometry, sp2 phase, and optical properties. Raman spectroscopy reveals an increase in sp2-bonded carbon and a continual structure ordering of the sp2 phase with increasing substrate temperature at deposition. Thermal desorption spectroscopy analysis revealed that the onset temperature of CH4 effusion of PECVD a-C:H films increase with increasing substrate temperatures, implicating enhanced structural stability via elevating the substrate temperature at deposition. The extinction coefficient k measured from spectroscopic ellipsometry gradually increases with increasing substrate temperature at deposition, due possibly to the graphitization effect which decreases the optical gap resulting in higher k.