Engineering Surface Oxygen Vacancies in $\mathrm{SrTiO_3}$ to Form a High Mobility and Transparent Quasi Two dimensional Electron System

TL;DR

This paper demonstrates a novel low-energy plasma method to engineer surface oxygen vacancies in SrTiO3, creating a high-mobility, transparent quasi-2D electron system with quantum oscillations and tunable confinement, suitable for optoelectronic applications.

Contribution

It introduces a new plasma-based technique to control surface oxygen vacancies in SrTiO3, enabling high mobility, transparency, and quantum phenomena in the resulting electron system.

Findings

Achieved electron mobility up to 20,000 cm^2V^{-1}s^{-1}.

Observed quantum oscillations and Kondo-like behavior under certain conditions.

Produced a transparent, lithographically patternable conductor with competitive figure of merit.

Abstract

Quasi-two-dimensional electron systems (q-2DES) are formed in various hetero-structures, including oxide interfaces. Oxygen vacancies (OVs) in oxides like $\mathrm{SrTiO_3}$ are known to produce electronic carriers. A novel way to produce $\mathrm{SrTiO_{3-\delta}}$ 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 $\mu \sim 20,000 \; cm^2V^{-1}s^{-1}$, 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 $\lambda$ $\sim 1.5$ $\mu m$ telecommunication wavelength.