IR laser photodeposition of a-Fe/Si films developing nanograins of ferrisilicate, iron disilicide and rare hexagonal iron upon annealing

摘要

IR laser-induced gas-phase photolysis of Fe(CO) _5-SiH _4 mixtures occurs as SiH _4-photosensitized decomposition of Fe(CO) _5 is accelerated by products of this decomposition and it results in deposition of amorphous Si/Fe nanocomposite films. Analyses of the deposited and subsequently annealed solid films were made by FTIR, Raman and X-ray photoelectron spectroscopy, X-ray diffraction and electron microscopy. The deposited films are amorphous, contain crystalline nanostructures of iron silicide FeSi _2 and undergo atmospheric oxidation in topmost layers to iron oxide and hydrogenated silicon oxide. Upon annealing they develop nanocrystalline structures of ferrisilicate, Fe _(1.6)SiO _4, carbon-encaged iron disilicide, FeSi _2, and very rare hexagonal (high-pressure) Fe surviving at ambient conditions. The mechanism of formation of these nanostructures is discussed in terms of gas-phase and solid-phase reactions.