Tailoring Film Chemistry Using Pulsed Plasma Polymerization of Acrylic Acid Precursor Monomer

Variable duty cycle pulsed plasma polymerization process is an effective technique to control film chemistry and deposition rate, thereby controlling film thickness. In the present investigation, the pulsed plasma polymerization technique was used to deposit thin films containing carboxylic groups on silicon wafer using acrylic acid (AA) as a precursor monomer. The thickness of films was measured with surface profiler. The wettability of films was evaluated by contact angle measurement with respect to water. Furthermore, these films were characterized by X-ray photo-electron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and atomic force microscopy (AFM) to understand film chemistry and surface roughness. The XPS results revealed that O/C ratio increased from 0.39 to 0.51 for continuous wave (CW) and 5-/25-ms pulse, respectively. Contact angle for the film deposited under CW condition was found to be 63.92°, which decreased systematically with the increase in off time of the pulse and finally reaches to 43.12° for the film deposited under 5-/25-ms pulse, indicating hydrophilic nature of the film. These results showed that pulsed plasma polymerization can be used for systematic control of film chemistry for various applications.