Self-limiting growth of metal fluoride thin films by oxidation reactions employing molecular precursors

FeF2 films are grown by the reaction of XeF2 and SeF6 with iron foil. The growth initially follows the Mott-Cabrera parabolic rate law, indicating that the process is diffusion limited. At a certain film thickness, however, the growth abruptly stops, with the thickness using XeF2 being nearly double that with SeF6. It is suggested that the shutdown is due to the inability of the molecules to dissociate when too far from the substrate and that SeF6 must approach more closely than XeF2. This work suggests the use of molecular precursors to grow thin films via a self-limiting chemical process.