Plasma enhanced chemical vapor deposition of high refractive index polymer films

Abstract

The refractive index is a key characteristic of polymer materials in optical applications. For organic polymers, typical refractive indices are in the range of 1.35 to 1.65. Extending the refractive index beyond the limits is of fundamental scientific interest and would enhance the utility of polymers in many applications. Polymeric thin films fabricated by plasma enhanced chemical vapor deposition (PECVD) have been investigated in the fields of electronics and optics and their utility is becoming more widespread in a variety of applications. Outstanding attributes of the PECVD photonic films include a smooth surface, dense crosslinking structure, robustness, environmental resistance, optical transparency in either visible or IR regions, and good adhesion to many optical window and substrate materials. In recent years, our laboratory has fabricated novel polymer optical coatings and films by PECVD. One focus of this research has been to expand the achievable maximum refractive index. This goal has been sought using two approaches including increasing the conjugation and crosslinking of chemical moieties of the bulk film and incorporation of metal ions into the structure. The techniques of XPS, FTIR, HRSEM, and ellipsometry were used to characterize both the optical properties and the chemical structure of plasma polymerized benzene, ferrocene, and metal-phthalocyanine thin films. The structure-property relationship and the effect of PECVD processing conditions are also discussed in this presentation.