Preparation and evaluation of amorphous metal oxide magnetic thin films and nanocomposites for spintronics

In this work, photochemical metalorganic deposition (PMOD) using thin films of metal 2-ethylhexanoates (Mo and Fe) was used to deposit patterned thin films of a-MoO3 and a-Fe 2O3 (where a stands for amorphous) in a positive tone. The mechanism of positive tone PMOD of a-Fe 2O3 was examined by using spectroscopic ellipsometry, which allowed the determination that the development preferentially removed the amorphous iron oxide from the film.;To gain an understanding of the local atomic structure of a-Fe 2O3, X-ray absorption spectroscopy was used to determine the oxidation state and coordination environment of the iron atoms in this amorphous material. It was found the iron is in the +3 oxidation state, and occupied an octahedral environment. Similarly, it was found that octahedral Co2+ and Fe3+ are present in a-CoFe 2O4 and that octahedral Cr3+ is present in a-Cr2O3. The local structure in these amorphous metal oxides a-MOx thin films is also discussed based on an analysis of the extended x-ray absorption fine structure (EXAFS). This represents the first determination of the local structure in a-MOx prepared by PMOD.;The magnetic properties of PMOD-prepared a-Fe2 O3, a-CoFe2O4, and a-Cr2O3 thin films were investigated. This work shows that these a-MOx thin films exhibit ferromagnetic properties at room temperature. Prior to this work, no magnetic amorphous iron oxide had previously been reported.;Iron(III) 2-ethylhexanoate was used as a precursor for direct-write electron beam induced lithography. The deposition of sub-100 nm iron oxide features was shown. Sub-40 nm nanowires with low line edge and width roughnesses (<3 nm) could be patterned. TEM and AFM inspection also identified free-standing, hollow nanotubes.;The magnetic properties of dense assemblies of spinel ferrite superparamagnetic nanocrystals were studied. This was done for nanocomposite thin films prepared by PMOD containing nanocrystals of one (gamma-Fe2O3 in a-MnO) or two chemical identities (gamma-Fe2O 3+CoFe2O4 in a-Al2O 3 and a-TiO2), and bulk binary mixtures of nanocrystalline powders (gamma-Fe2O3+CoFe 2O4). Based on the magnetic properties of these nanocomposite thin films and powders, a model in which strong, interparticle magnetic interactions affect the magnetic properties is presented.;Keywords. Metal oxide; thin films; magnetic films; magnetic nanocomposite; photolithography; amorphous magnets.