Iron-based inorganic–organic hybrid and superlattice thin films by ALD/MLD

Abstract

Here we present novel layer-by-layer deposition processes for the fabrication of inorganic–organic hybrid thin films of the (–Fe–O–C₆H₄–O–)_n type and also superlattices where thicker iron oxide layers alternate with monomolecular-thin organic layers. The processes are based on a combination of atomic layer deposition (ALD) and molecular layer deposition (MLD) techniques where the cyclopentadienyl iron dicarbonyl dimer (Cp₂Fe₂(CO)₄) is used as the iron source and hydroquinone (HQ) as the organic precursor. For the (–Fe–O–C₆H₄–O–)_n hybrid films a growth rate value as high as 3.7 Å per cycle was achieved at 180 °C. Superlattices where thin crystalline iron oxide layers of the magnetite structure alternate with single organic layers consisting of benzene rings were moreover successfully fabricated from the same precursors at 160 °C using water as the source of oxygen in the ALD cycles for the magnetite layers. We foresee that our new ALD/MLD processes offer a valuable novel tool to modify the properties of magnetite thin films and even more widely possess the potential to boost the ALD/MLD research frontier on functional transition metal oxide based thin films.