Photonic thin films have been grown on a variety of substrates using plasma-enhanced chemical vapor deposition (PECVD) of organic monomers, namely benzene and octafluorocyclobutane (OFCB). Films produced by both homo-polymerization and co-polymerization have been prepared and analyzed. In order to introduce significant contributions from OFCB into co-polymerized films, the OFCB was introduced directly into the plasma zone and the benzene flow was reduced to a low, stable level using a high-accuracy metering valve. The films have been characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and variable-angle spectroscopic ellipsometry (VASE), with an emphasis on XPS. Apart from determining the atomic composition of the films with XPS, it was extremely valuable in determining the chemistry of the films. Studies of the mechanisms of the homo- and co-polymerization reactions have aided in the fabrication of photonic films.

We have developed plasma copolymerization techniques to fabricate photonic films with two (or more) monomers, whose composition can be controlled to manipulate the optical properties of the films. Spectroscopic ellipsometry confirmed that by changing monomer feed ratios (benzene and octafluorocyclobutane), films in the nanometer thickness range with refractive indices between those of the homopolymerized films could be fabricated. Spectroscopic analysis of the chemical structure of the copolymerized films using FTIR and XPS confirmed a nonlinear variation of chemical composition as a function of the monomer feed ratios. However, the refractive index of these films changes linearly with the film composition (characterized as the fluorine/carbon ratio). Facile control of optical thickness was demonstrated by fabricating multilayer antireflecting (AR) coatings on substrates of differing refractive indices. Very good agreement between the design and experimental spectra was obtained. This growth process creates a new way to prepare gradient-index (GRIN) films in the nanometer range, with a Deltan greater than 0.3 and with well-controlled properties.

A multilayer optical interference film has been developed using plasma-enhanced chemical vapor deposition (PECVD) of different organic precursor materials. A relatively large refractive index contrast for polymers (>0.2) is achieved by sequential plasma polymerization (PP) of octafluorocyclobutane (OFCB) and benzene. Gas-phase molecules of both precursors, excited by an argon plasma in a flowing afterglow reaction chamber, are deposited on a variety of substrates to form dense, pinhole-free, cross-linked polymer films. The PP-OFCB film yields a refractive index of 1.40, whereas PP-benzene exhibits a refractive index of 1.61 at 500 nm. We report here on the chemical (FTIR and XPS), optical (variable angle spectroscopic ellipsometry and UV−Vis spectrometry), and morphological (scanning electron microscopy) characterization of individually polymerized films of each component. These data are used to design a multilayer film with a notch at ∼1 μm. A ten-bilayer stack (alternating high and low refractive index)...