Readme for dataset relating to Enhanced performance in transparent conducting materials at the interface of a wide band gap semiconductor and a correlated metal
Jessica L. Stonera, Maria Batukc, Troy D. Manningb, Matthew S. Dyerb, Joke Hadermannc, Matthew J. Rosseinskyb*, and Jonathan Alariaa* 

a Department of Physics and Stephenson Institute for Renewable Energy, University of Liverpool, Oxford Street, L69 7ZE, UK
b Materials Innovation Factory, Department of Chemistry, University of Liverpool, 51 Oxford Street, L7 3NY, UK
c Electron Microscopy for Materials Science (EMAT), University of Antwerp, Groenenborgerlaan, 171, B2020 Antwerp, Belgium

All files are human readable acsii format (.csv, .txt, .asc). AFM files are in .mi format which can be processed in the open source software Gwyddion.

Sample preparation: Thin film samples of SrNbO3 were deposited via pulsed laser deposition (PVD Products NanoPLD, Coherent Lambda Physik COMPex Pro 248 nm KrF Excimer laser) on SrTiO3 (001) substrates (PI-KEM, UK). Dense ceramic targets of Sr2Nb2O7 were prepared via conventional solid state synthesis. Stoichiometric amounts of SrCO3 (>99.9% purity) and Nb2O5 (99.9985% purity) were weighed, ground thoroughly in an agate mortar and pestle and calcined in air at 900 °C for 12 hours, re-ground and fired again in air at 1200 °C for a further 12 hours. The resulting powder was pressed into a 32 mm diameter pellet and then pressed with a cold isostatic press at 30 kpsi before sintering at 1450 °C for 24 hours. Heating and cooling was at a rate of 5 °C per minute for all steps. Deposition was performed under chamber base pressure (~5×10-7 Torr) with nominal substrate temperature of 650 °C and a laser fluence of 1.3 J cm-2 at a rate of 1 Hz. 

X-ray diffraction:
X-ray diffraction: Powder X-ray diffraction of the target material was performed on a Panalytical Co source (wavelength = 1.79 Å) instrument in Bragg-Brentano geometry. X-ray analysis of thin films was performed on a Rigaku Smartlab diffractometer, with Cu source (wavelength = 1.54 Å) and a 2D Hypix detector in 1D mode for large angle theta-2theta scans and reflectivity and 0D for rocking curve analysis. Film thicknesses >5 nm were determined by X-ray reflectivity and used to calibrate the growth rate per laser pulse for deposition of films with nominal thickness <5 nm.

Electron microscopy: The sample was prepared using the focused ion beam (FIB) technique. The film was covered with carbon and platinum protection layers. For the high angle annular dark field scanning transmission electron microscopy (HAADF-STEM) imaging and STEM-EDX analysis, a probe aberration corrected microscope FEI Titan operated at 300 kV and equipped with Super-X detector was used. The structure model of the film was made in CrystalMaker software by merging cubic SrTiO3 and SrNbO3. For the interface layer, different Ti/Nb contents were tested: 0.3Ti+0.7Nb; 0.5Ti+0.5Nb; 0.7Ti+0.3Nb and a sharp interface. The simulated HAADF-STEM images were calculated using the QSTEM 2.5 software.
XANES: X-ray absorption near edge structure was obtained at Diamond Light Source beamline B18 in reflection geometry. Niobium oxidation states was calibrated using NbO2 (Nb4+), Nb2O5 (Nb5+), Sr2Nb2O7 (Nb5+), La1/3NbO3 (Nb5+) and a 0.5 wt% Nb5+ doped SrTiO2 single crystal substrate.

Electrical properties: Resistivity measurements were obtained using a Quantum Design Physical Properties Measurement System (PPMS) capable of a temperature range of 300K to 2K and applying magnetic fields up to a magnitude of 14T. The films were contacted in Van der Pauw geometry.

Optical properties: UV-vis-NIR transmission spectra were obtained using a Agilent Cary 5000 between 2500 nm and 200 nm, with reduced slit height setting. The NIR (2500-900 nm) scan rate was 12 nm/min and the UV-vis scan rate was 600 nm/min, with a measurement interval of 0.667 nm. Average visible transmission was calculated between 400 nm and 800 nm. Ellipsometry in the UV–NIR range was performed using a J. A. Woollam M200UI with a wavelength range of 240 to 1700 nm (0.73–5.14 eV). Ellipsometry in the IR range was performed using a J. A. Woollam Mark II IR Variable Angle Spectroscopic Ellipsometry instrument with a wavelength range of 1.25 to 40 ?m (0.031–1 eV).

Atomic Force Microscopy: The surface morphology of the films were studied by atomic force microscopy with an Agilent 5600LS Microscope in tapping mode with a scan area of 2 micron x 2 micron.

Computational Details: Periodic DFT calculations were performed on a twelve-layer slab model containing six layers each of SrTiO3 and six layers of SrNbO3. Both surfaces of the slab were terminated with SrO layers and separated by a vacuum region of 32.3 Å. All calculations were carried out using VASP with the PAW approach to treat core electrons and a 550 eV plane-wave cutoff energy. The meta-GGA functional SCAN was used to reduce the overestimated delocalisation of electron density common in GGA functionals. Calculations were performed in a fixed 3.908 Å × 3.908 Å × 80 Å cell where the in-plane parameters were chosen to match those of SrTiO3 representing growth on a fixed substrate. A dipole correction layer was placed in the vacuum region to counter the periodic dipole moment generated by the asymmetric slab. The positions of all atoms were optimized until forces fell below 0.01 eVÅ?1 using an 11×11×1 k-point grid. A single-point calculation of the partial density of states was then performed with a 24×24×1 k-point grid.