OPTICAL-PROPERTIES OF POLYMERIC THIN-FILMS GROWN BY CHEMICAL-VAPOR-DEPOSITION

For the first time, the refractive index of polyparaxylylene films, th e only polymers grown commercially by chemical vapor deposition (CVD), is reported throughout the visible spectrum. This information is requ ired if optical components such as antireflective coatings or waveguid es are to be fabricated with CVD polymers. These properties are compar ed to a low-index CVD copolymer, poly(parachloroxylylene-co-perfluoroo ctyl methacrylate), invented in our laboratory. The ellipsometric cons tants psi and delta were measured for wavelengths between 400 nm and 1 000 nm using variable angle spectroscopic ellipsometry; many samples o f each film were grown to improve statistics. The data were modeled as suming a birefringent Cauchy dispersion; excellent agreement between m odels and experimental data was obtained. The refractive index (lambda = 632.8 nm) of the copolymer in the film plane was 1.389, compared to 1.645-1.665 for the homopolymers. PPX, PPX-C, and the copolymer showe d negative birefringence, while PPX-D showed positive bifringence. The optical properties of PPX showed little thickness dependence for film s ranging from 36 nm to 2100 nm thick.