Silicon nitride films deposited on silicon substrates by several techniques were studied. Electron diffraction studies of the films revealed that films varied in crystallite size from <10 to ∼100Aå. Radiotracer diffusion experiments using Na22 as diffusant revealed that the smaller crystallite films were better barriers to sodium diffusion than the larger crystallite films. Field enhanced drift of sodium was not observed in any of the silicon nitride films regardless of crystallite size. Silicon nitride films composed of large crystallites appeared to etch faster than smaller crystallite films in dilute buffered hydrofluoric acid.