A micro-pulse process of atomic layer deposition of iron oxide using ferrocene and ozone precursors and ti-doping

Hematite (α-Fe₂O₃) thin films are obtained by atomic layer deposition (ALD) in the temperature range 200 - 350°C using ferrocene and ozone as the precursors. A micro-pulse process facilitates the precursor adsorption and shortens the ferrocene dose time to 5 s. When tested on Si(100) substrates, the growth rate is around 0.5 Å per cycle for the first 300 cycles, after which the growth becomes nonlinear. Interestingly, a linear growth can be maintained with a rate of ≈0.55 Å per cycle by TiO₂ co-deposition (cycle ratio of TiO₂/Fe ₂O₃ = 1:20). Characterizations by X-ray photoemission spectroscopy (XPS), Raman spectroscopy (RS), and UV-vis absorption confirm the presence of the α-Fe₂O₃ phase after post-deposition annealing. Uniform depositions on dense ZnO nanorod arrays and anodic aluminum oxide (AAO) templates are also demonstrated, inferring that the current process is capable of coating on high (>50) aspect ratio structures. A micro-pulse ALD process is developed for fast deposition of Fe₂O₃ on both planar and high aspect ratio substrates (nanowires and AAO channels). By introducing TiO₂ co-deposition, a linear growth rate can be maintained up to 600 cycles, corresponding to a thickness of 33 nm. A controllable Ti-doping into Fe₂O₃ films is achievable by adjusting the ALD cycle ratios of TiO₂ and Fe₂O ₃.