Talos stem

Structural characterisation was performed by XRD employing a PanAnalytical Pro Diffractometer. The spot size was set to $5\times 5{\mathrm{mm}}^2$ via a $10\mathrm{mm}$ height-limiting slit, $2^{\mathrm{rad}}$ Soller slits and a programmable divergence slit. The scan step size was $0.{0083556}^{\circ }$ with a time per step of $1998.345\mathrm{s}$ in a range of ${25}^{\circ }-{40}^{\circ }$ . The very long step time was required due to the small sample size and amorphous nature of the room-temperature sputtered ITO films^{9 (link),53 (link)}. The range was chosen to cover the most clearly identifiable ( $222$ ) and ( $400$ ) Bragg peaks for bixbyite In₂O₃ ( $\mathrm{a}=1.0118\mathrm{nm}$ )^{31 (link)}, at $30.6^{\circ }$ and $35.5^{\circ }$ , respectively. Cross-sectional images of an indicative set of ITO thin films were obtained via high resolution TEM (FEI™ Talos sTEM) using a Schottky-type field emission gun operated with an electrostatic potential of $200\mathrm{kV}$ . Prior to TEM, the films were subjected to focused ion beam milling process using a JEOL 4500 FIB/SEM.

Surface elemental characterisation was performed with a Kratos Analytical Ltd. AXIS Ultra XPS system using a monochromated Al-K_α1 X-ray beam excitation source ( $1486.6\mathrm{eV}$ ) in an ultra-high vacuum chamber (base pressure $\sim {10}^{-9}\mathrm{bar}$ ). The relative elemental abundance across the entire depth of the ITO thin films was determined from EDX measurements with the FEI™ Talos sTEM.