Process-Induced Chemical Reactions on Interfaces of Thin Film Ionic Materials

Thin-film samples were fabricated in an AJA Orion 8 magnetron sputtering system equipped with an in-situ mask exchanger, enabling sequential deposition of multiple material configurations without air exposure. A thermally oxidized silicon wafer (500 nm SiO₂) served as the substrate, with a 10 nm Ti / 100 nm Pt bilayer deposited by electron-beam evaporation as the current collector. A 50 nm V₂O₅ film was deposited by reactive RF sputtering from a 2-inch V₂O₅ target (7.5 W/cm², 2 mTorr, 92% Ar / 8% O₂). LiPON overlayers were deposited by reactive RF sputtering from a 2-inch Li₃PO₄ target (3.2 W/cm², 2 mTorr, N₂ atmosphere) to target thicknesses of 10 nm (30 min) and 20 nm (60 min). Li₂O overlayers were deposited by RF sputtering from a 2-inch Li₂O target (3.9 W/cm², 2 mTorr, Ar atmosphere) to target thicknesses of 10 nm (15 min) and 20 nm (30 min). Wedge-shaped shadow masks were used to define distinct deposition regions on the same wafer. Copper top contact pads (2 mm diameter) were deposited through an array mask via DC sputtering. Half of each wafer was post-annealed at 300 °C for 3 hours in a low-N₂ atmosphere (5 mTorr). Optical thickness and constants were determined by spectroscopic ellipsometry (J.A. Woollam M-2000D) at three incident angles (55°, 60°, 65°) over the 192–1688 nm wavelength range, using Tauc-Lorentz oscillator models for V₂O₅ and Cauchy models for the overlayers, all constrained by Kramers-Kronig consistency. Structural characterization was performed by Raman spectroscopy (H-J-Y Raman Microscope, 633 nm laser, 2.1 mW, 860 nm spot size; triplicate acquisitions of 60 s each). Surface and depth composition were measured by X-ray photoelectron spectroscopy (Kratos Axis Ultra DLD, Al Kα source); surface spectra used a 160 eV pass energy for surveys and 20 eV for high-resolution spectra, with charge correction referenced to adventitious carbon at 284.5 eV. XPS depth profiling was performed using a 5 kV Ar⁺ ion beam with a Wien mass filter, with Shirley background subtraction and Gaussian-Lorentzian peak fitting in CasaXPS. Electrochemical measurements were collected with a BioLogic VSP-300 potentiostat in an Ar-filled glovebox using a two-electrode micromanipulator setup. Potentio-electrochemical impedance spectroscopy (PEIS) was conducted at open-circuit voltage with a 10 mV sinusoidal perturbation over 300 kHz to 250 mHz. Electronic conductivity was assessed by DC-relaxation chronoamperometry (CA), applying a constant voltage for 15 minutes per step across four voltage intervals (0–200 mV in 50 mV steps). The raw data archive is organized by measurement technique: DC-relaxation (CA files), EIS (PEIS files), ellipsometry (optical parameter files), Raman spectroscopy (intensity vs. wavenumber text files), surface XPS, and XPS depth profiles (VAMAS-format .vms files). File naming conventions encode the sample identity, deposition conditions, and measurement date.