Engineering Surface Oxygen Vacancies in $\mathrm{SrTi}{\mathrm{O}}_3$ to Form a High Mobility and Transparent Quasi Two dimensional Electron System

Abstract

Quasi-two-dimensional electron systems (q-2DES) are formed in various hetero-structures, including oxide interfaces. Oxygen vacancies (OVs) in oxides like $\mathrm{SrTi}{\mathrm{O}}_3$ are known to produce electronic carriers. A novel way to produce $\mathrm{SrTi}{\mathrm{O}}_{3-\hat{\mathrm{I}}´}$ on the surface using a low-energy ${\mathrm{H}}_2$ plasma is shown here. It results in a q-2DES with mobility as high as $\hat{I}¼\sim 20,000c{m}^2{V}^{-1}{s}^{-1}$, displaying quantum oscillations in magneto-resistance. We can achieve a sharper or weaker confinement potential by adjusting the process pressure. The system with sharper confinement displays clearer quantum oscillations and Kondo-like temperature dependence of resistance. OVs close to the surface behaving like a correlated Anderson impurity is responsible for the Kondo behaviour. Quantum oscillations are less prominent in the weakly confined system. A cross-over from weak-localization to anti-localization with temperature is seen, but no Kondo behavior. The process also results in a transparent conductor amenable to lithographic patterning. This conductor's standard figure of merit is comparable to poly-crystalline ITO films in the visible regime and extends with similar performance into the $\hat{I}»$ $\sim 1.5$ $\hat{I}¼m$ telecommunication wavelength.