Stoichiometry variation for the atomic layer deposition of SrxTiyOz from Sr(iPr3Cp)2, Ti[N(CH3)2]4 and H2O

• SrxTiyOz layers were grown from commercial precursors at a commercial ALD device.
• Stoichiometric as well as layers with Sr or Ti excess can be deposited.
• At a deposition temperature of 320 °C the layers are free of carbon.
• A direct correlation between Sr content, optical properties and GPC was determined.
• Ex situ annealing at 600 °C yields completely crystallized SrTiO3 layers.

The atomic layer deposition (ALD) of stoichiometric SrTiO3 as well as layers with either Sr or Ti excess from the commercial precursors Bis(tri-isopropylcyclopentadienyl)-strontium Sr(iPr3Cp)2, Tetrakis-(dimethylamido)titanium(IV) Ti[N(CH3)2]4 and H2O on a commercial ALD system is demonstrated. The influence of the stoichiometry on the optical layer properties was investigated. Spectroscopic ellipsometry shows that all SrxTiyOz layers are transparent up to the optical gap energy, which amounts to 3.87 eV for stoichiometric SrTiO3. A direct correlation between the Sr content, optical properties, layer density and the growth per cycle value was determined. X-ray photoelectron spectroscopy after Ar ion cluster sputtering indicates that the layers are free of carbon. After ex situ annealing under atmospheric conditions we observed a change in microstructure from amorphous to polycrystalline starting at 545 °C by atomic force microscopy and grazing incidence X-ray diffraction. Electrical I–V measurements show very small leakage currents confirming the insulating character of the SrxTiyOz layers.