Binary Thin Films from Molecular Precursors

The ferraboranes B2H6Fe2(CO)6 and [B2H4Fe2(CO)6]2 have been investigated as volatile precursors for the deposition of thin iron boride films with composition FeB. The thermal decomposition of B2H6Fe2(CO)6 on glass or aluminum substrates at 175-250°C at pressures between 10-5 and 10-4 Torr results in the deposition of uniform, amorphous alloy films of average composition Fe56B44 contaminated with 2-4% carbon and oxygen impurities. Individual film thicknesses ranged from 1000 to 6000 Å. Mössbauer effect spectra of these films, when compared with those from films prepared from HFe3(CO)9BH4, show that a random packing model does not apply and that local structure exists in these films. Crystallization of these films at 600°C followed by X-ray diffraction and Mössbauer spectroscopic examination reveals the formation of two phases, namely, Fe2B and FeB. Although the structures of these two phases are the same as those produced by conventional high-temperature routes, the latter phase exhibits significantly different Mössbauer behavior. Utilization of [B2H4Fe2(CO)6]2 as a precursor yields films of similar composition. Crystallization leads again to Fe2B and FeB and no significant differences in the films formed from the two different precursors were observed