Surface structures tailoring of hexamethyldisiloxane films by pulse rf plasma polymerization

The surface structures of hexamethyldisiloxane (HMDSO) films prepared by rf plasma polymerization are investigated by Fourier transform infrared, solid-state 29Si CP/MAS nuclear magnetic resonance and scanning electron microscope. The reactive species in HMDSO plasma and the mechanism of HMDSO plasma synthesis are studied by optic emission spectrum. The effect of continuous wave discharge and different pulse discharge parameters especially plasma “high power” time on chemical structure and physical morphology modifications of HMDSO polymer film is compared elaborately. The results show that HMDSO-continuous-wave polymer is an organic film without Sisingle bondO group. Its surface consists of several microscale islands with many clustered rods. While HMDSO-pulse-polymer is a network of interconnected primary methylsiloxane units and minor hydroxyl, oxymethylene, hydrogen and carbonyl groups. The ratio of Sisingle bondOsingle bondSi to Sisingle bond(CH3)n and new functional groups of single bondOH, Cdouble bond; length as m-dashO and Csingle bondO are effectively “tailored” by changing plasma “high power” time. Moreover, HMDSO-pulse-polymer is a continuous, regular and compact film with a few asteroid protuberances. This deposited film becomes more regular after increasing plasma “high power” time and gradually presents perfect “straw-mat” morphology. It is indicated that pulse plasma polymerization is an effective way to tailor the surface structures of plasma polymer films through controlling plasma “high power” time.