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Bruce F. Bowden Department of Chemistry, School of Pharmacy and Molecular Sciences, James Cook University, Townsville QLD 4811, Australia (Received 5 October 2010; accepted 12 January 2011)

The development of novel organic polymer thin films is essential for the advancement of many emerging fields including organic electronics and biomedical coatings. In this study, the effect of synthesis conditions, namely radio frequency (rf) deposition power, on the material properties of polyterpenol thin films derived from nonsynthetic environmentally friendly monomer was investigated. At lower deposition powers, the polyterpenol films preserved more of the original monomer constituents, such as hydroxy functional groups; however, they were also softer and more hydrophilic compared to polymers fabricated at higher power. Enhanced monomer fragmentation and consequent reduction in the presence of the polar groups in the structure of the high-power samples reduced their optical band gap value from 2.95 eV for 10 W to 2.64 eV for 100 W. Regardless of deposition power, all samples were found to be optically transparent with smooth, defect-free, and homogenous surfaces.

I. INTRODUCTION

Recent advancements in organic electronics systems, such as flexible electronic circuits, displays, sensors, thin-film transistors, and thin-film organic photovoltaic devices, are in demand for the development of new highperformance organic materials with properties comparable to those of existing electronic materials.1–6 Radio frequency (rf) plasma-enhanced chemical vapor deposition (PECVD) is commonly used for fabrication of such materials to be applied in the microelectronic industry, because they allow deposition of organic compounds that do not contain functionalities associated with conventional polymerization (such as C5C unsaturation7) on a variety of low-cost substrates, including glass, plastic, metal foils, etc.2,3 Thin films manufactured by means of rf PECVD exhibit high spatial uniformity and adhesion to the substrate and possess smooth and pinhole-free surfaces.8,9 In addition, the conditions of nonequilibrium plasma techniques allow for the formation of chemically functionalized polymer thin films that retain some of the original functionalities and structure of the monomer while taking advantage of inherent properties of the substrates.5,10 In the process of PECVD, the gas-phase and surfacerelated plasma reactions are influenced by a number of conditions, such as the nature of the plasma, the mode of a)

Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2011.23 1018

J. Mater. Res., Vol. 26, No. 8, Apr 28, 2011

http://journals.cambridge.org

Downloaded: 25 Mar 2015

transferring energy from the generator into the reaction chamber, the geometry of the chamber, and the deposition conditions; for example, monomer flow, pressure, nature of the substrate and its temperature, and the input power. In the course of plasma-enhanced synthesis, the monomer is dissociated with the degree of dissociation closely rel