Synthesis of PECVD a-SiC XN Y:H membranes as molecular sieves for small gas separation

Abstract

Plasma enhanced chemical vapor deposition (PECVD) a-SiC X N Y :H thin films have been studied as molecular sieve membranes for light (hydrogen, helium) gas separation at room temperature up to 150 °C. The microstructure of the deposited materials and their thermal stability have been characterized as a function of the electric plasma power and the ratio between the vapor precursors – hexamethyldisilazane and ammonia – using SEM, Fourier transformed infrared spectroscopy (FTIR), EDS, thermo-gravimetric analysis (TGA) and ellipsometry. Single gas permeation tests have also been carried out. An ideal selectivity of helium over nitrogen of 50 has been obtained at 150 °C with a helium permeance of about 10 −7 mol m −2 s −1 Pa −1. These promising PECVD materials developed for gas separation also revealed a chemical stability up to 500 °C, even in oxidative atmosphere.