Growth of iron cobaltoxides by atomic layer deposition

Abstract

Thin films of iron cobalt oxides with spinel-type structure are made by the atomic layer deposition (ALD) technique using Fe(thd)3 (Hthd = 2,2,6,6-tetramethylheptane-3,5-dione), Co(thd)2, and ozone as precursors. Pulse parameters for ALD-type growth are established and such growth can be achieved at deposition temperatures between 185 and 310 degrees C. Films have been deposited on amorphous soda-lime glass and single-crystalline substrates of Si(100), MgO(100), and alpha-Al2O3(001) which all provide crystalline films, but with various orientations and crystallite sizes. Application of an external magnetic field during the film growth does not influence film growth characteristics (growth rate, crystallinity, topography etc.). Magnetization data are reported for phase-pure films of spinel-type structure with composition Fe2CoO4.

(Invited) Reaction Mechanisms in ALD of Ternary Oxides

“…As with LaMnO x , these data alone do not tell whether mechanism A or B is valid; however, strong indications supporting transfer of thd ligands away from Mn can be found in the same manner as presented for growth of LaMnO x above. As shown in Figure 3, the five data points for cobalt iron oxide grown at 185 °C (8) show a spread about the predicted curves for both mechanism A and B, the best fit for the latter being (fCo+1)/(fFe+1)=1.1±0.2. However the convex upward shape of the stoichiometry curve is reproduced well, and this may again be traced to the lower charge of the metal cation in Co(thd) 2 relative to that in Fe(thd) 3 .…”

Low Temperature Stabilization of Nanoscale Epitaxial Spinel Ferrite Thin Films by Atomic Layer Deposition

“…[ 11,31 ] From high resolution in-plane ϕ-2θ area scans, the strain and out-of-plane lattice parameter has been analyzed for 15 nm CFO on STO (100), Figure 1 The strain state of these ALD-CFO thin fi lms is dramatically different from the CoFe 2 O 4 oxide spinels prepared at higher temperature by sputtering, pulsed laser deposition, molecular beam epitaxy, and even atomic layer deposition after a post annealing treatment. [ 11,31 ] From high resolution in-plane ϕ-2θ area scans, the strain and out-of-plane lattice parameter has been analyzed for 15 nm CFO on STO (100), Figure 1 The strain state of these ALD-CFO thin fi lms is dramatically different from the CoFe 2 O 4 oxide spinels prepared at higher temperature by sputtering, pulsed laser deposition, molecular beam epitaxy, and even atomic layer deposition after a post annealing treatment.…”

Cobalt Ferrite Nanocrystallites for Sustainable Hydrogen Production Application

“…These techniques are also not suited to obtain conformal coatings on curved substrates. Furthermore, these techniques are inapplicable when the target material is maintained at low-temperatures, as an irradiation would lead to instantaneous decomposition of the target material [11]. There is, therefore, a need to develop simple and inexpensive wet chemical approach for synthesizing ferrite nanostructures on variety of substrates at ambient temperature.…”