Cobalt hexafluoroacetylacetonate polyether adducts for thin films of cobalt oxides

Abstract

The novel [Co(C 5F 6HO 2) 2 · 2H 2O · CH 3(OCH 2CH 2) 2OCH 3] and [Co(C 5F 6HO 2) 2 · 2H 2O · CH 3(OCH 2CH 2) 3OCH 3] low-melting adducts have been synthesized and characterized by elemental analysis, IR spectroscopy, mass spectra and TG–DTG thermal measurements. The former adduct is liquid at room temperature, whilst very mild heating of the latter results in a thermal stable liquid compound. Both adducts can easily be evaporated. Deposition experiments, in a low-pressure horizontal hot-wall reactor, on optical transparent SiO 2 substrates, using these precursors, result in CoO or Co 3O 4 films, depending on the deposition conditions. XRD measurements provide evidence that CoO and Co 3O 4 consist of cubic, highly oriented, (2 0 0) and (3 1 1) crystals, respectively. The mean crystallite sizes were evaluated from the XRD line broadening. Both optical spectra and resistivity measurements of Co 3O 4 films show that they are semi-conducting and their band-gap was determined from the optical induced transitions. The film cross section and the surface atomic composition were investigated by SEM and XPS analyses, respectively.