Subnanoporosity development in hydrocarbon-siliconoxide hybrid PECVD films elucidated by variable-energy positron annihilation

Abstract

Variable-energy positron annihilation spectroscopy was applied to the investigation of nanopore formation in hydrocarbon-siliconoxide hybrid films fabricated through plasma enhanced chemical vapor deposition. Positron lifetime and Fourier transform infrared absorption measurements revealed that the pore size increases from 0.4 to 0.8 nm in radius with increasing annealing temperature, illustrating that the formed pores are in the micropore range. Based on a one-dimensional diffusion model, the ortho-positronium diffusion length was estimated from the variation of the positron 3γ decay probability for the films annealed with various temperatures as a function of positron incident energy. The result suggested that the pore interconnectivity during the pore formation by annealing depends on the gradual decomposition of the carbonaceous component.