A comprehensive study of valence band structure and work function in DLC and Q-carbon films using Photoelectron Spectroscopies

Diamond-like carbon (DLC) and quenched carbon (Q-carbon) are two types of amorphous carbon whose properties depend on the sp²-sp³ carbon content. Due to the suitability and potential of these materials in electronic applications and device fabrication, it is important to analyze the effects of the composition on the work function and valence band structure of these thin films. In this study, DLC films having different sp²-sp³ ratios are deposited using pulsed laser deposition (PLD), and Q-carbon is fabricated through subsequent pulsed laser annealing (PLA) of the DLC films. X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS) are utilized to investigate the chemical composition, valence band, and work function of nitrogen-doped and undoped DLC and Q-carbon films. The results indicate that the valence band structure strongly depends on both the nitrogen partial pressure and the ratio of sp²-sp³ carbon. The C 1s peak study indicates a significant shift to higher binding energy with doping while the D-parameter of the C KLL peak provides an extensive understanding of the newly discovered Q-carbon structure. The results obtained from this study will provide a roadmap to develop a comprehensive understanding of the electronic band structures and workfunctions of amorphous carbon films, especially Q-carbon, which holds great promise for different electronic applications, i.e. electron field emission devices, superconductivity, sensing devices, etc.