Surface Characterization of Thin Polymer Films Deposited by Plasma Enhanced Chemical Vapor Deposition Via Water Angle Measurement

The purpose of this experiment is to explore the use of plasma polymerization in the preparation of thin polymer thin films for microelectronic, and sensor applications ranging from the fabrication of organic and inorganic optoelectronic structures to implantable medical devices. This method provides for the preparation of conformal coatings of predictable chemical structure and functionality by appropriate choice of film precursor (monomer) and operating conditions for the plasma discharge. The purpose of the coating is to either limit or prompts the tissue growth when the device is implanted in human body depending on the application. Issues relating to adhesion, selective permeation and protection of the sensor or electronic structures can be addressed through the wide range of properties which can be imparted to the layered structure of such systems.

Of particular importance to the understanding of the stability and performance characteristics of such films within the ultimate device structure is the surface energy, surface tension and solvent compatibility of the plasma polymerized thin films. A practical approach to characterize the surface properties and energetics, along with compatibility of the films in the host environment in the long term involves the use of the sessile drop method of contact angle (CA) measurement, using the appropriate testing water on Teflon-like surface film precursors for fluorocarbon films and 1-octen (1-OT) for hydrocarbon films which were introduced in the gas run on sentence break into 2 or 3 phase into a plasma reactor powered at 13.56 MHz through a capacitively coupled external electrode. Where transform IR (FT-IR) experiments allow for the analysis of the bulk of the deposited films, contact angle measurement using water as the test liquid probe the surface polarity and stability of those materials. In all cases, the surface energies and solvent compatibilities can be measured immediately after preparation by contact angle measurements, and their stability over time can also evaluated conveniently by this technique.

Contact angle measurements have also been applied to surface characterization of thin polymer films deposited on silicon and indium tin oxide substances.