Deposition and characterization of dense and stable amorphous hydrogenated boron films at low substrate temperatures

Amorphous hydrogenated boron (a-B:H) thin films were prepared by radio-frequency plasma chemical vapor deposition of B2H6 diluted in hydrogen. The influence of deposition parameters on chemical composition and structural properties were determined by ion beam analysis, Fourier transform infrared (FTIR), X-ray photoelectron (XPS) and thermal desorption (TDS) spectroscopy. FTIR and XPS analysis show differences in film stability depending on ion energy. Films deposited at low substrate temperatures and low ion energies undergo chemical changes when exposed to atmosphere. XPS and FTIR revealed that these chemical changes are accompanied by an incorporation of carbon and oxygen into the bulk of the film. Stable films were prepared at substrate temperatures as low as 330 K if the ion energy is sufficiently high (self-bias voltages > 150 V). No chemical changes of these films were observed after 15 months of exposure to ambient atmosphere. Chemical stability correlates with boron density which lies between 1.6-1.85 g/cm(3) for stable films.