Compressive thermal stress and microstructure-driven charge carrier transport in silicon oxycarbide thin films

This work correlates the charge carrier transport mechanism of silicon oxycarbide-based thin films with their morphology and thermal stress. Segregation of highly-graphitized carbon-rich, oxygen-depleted C/SiC areas homogeneously dispersed within an oxygen-rich C/SiOC matrix was seen on the 500 nm-SiOC thin films. Compressive biaxial stress induced by the mismatch with the Si-substrate thermal expansion coefficient was calculated at 109 MPa. Through Hall measurements, p-type carriers were shown dominating the SiOC film similar to monolithic samples. Thin films and monoliths have comparable carrier concentrations while the carrier mobility in SiOC thin films was 2 magnitudes higher than that of monolithic samples and is considered a consequence of the compressive thermal stress acting on the film. Improved conductivity of 16 S cm-1 is measured for the SiOC thin film sample which is assumed considering the enhanced carrier mobility alongside the reduced percolation threshold ascribed to the phase-separated morphology of the thin film.

Automated summary

This study investigates the charge carrier transport mechanism in silicon oxycarbide thin films, finding that highly-graphitized carbon-rich areas are dispersed within an oxygen-rich matrix, leading to compressive biaxial stress. Hall measurements show p-type carriers dominating the SiOC film, with carrier mobility two magnitudes higher than in monolithic samples. The improved conductivity of the SiOC thin film is attributed to enhanced carrier mobility and a reduced percolation threshold due to the phase-separated morphology.