# Observation of a two-dimensional electron gas at CaTiO$_3$ film surfaces

## TL;DR

This study demonstrates the existence of a two-dimensional electron gas at the surface of CaTiO$_3$ films, revealing potential for oxide-based electronic applications and expanding the understanding of surface electronic states in titanates.

## Contribution

It provides experimental evidence of a 2DEG on CaTiO$_3$ surfaces and explores surface reconstructions affected by UV-light, broadening the scope for oxide electronics research.

## Key findings

- 2DEG observed with a 400 meV occupied band width
- Surface reconstruction changes from c(4x2) to p(2x2) under UV-light
- CaTiO$_3$ joins other oxides with surface 2DEGs

## Abstract

The two-dimensional electron gas at the surface of titanates gathered attention due to its potential to replace conventional silicon based semiconductors in the future. In this study, we investigated films of the parent perovskite CaTiO$_3$, grown by pulsed laser deposition, by means of angular-resolved photoelectron spectroscopy. The films show a c(4x2) surface reconstruction after the growth that is reduced to a p(2x2) reconstruction under UV-light. At the CaTiO$_3$ film surface, a two-dimensional electron gas (2DEG) is found with an occupied band width of 400 meV. With our findings CaTiO$_3$ is added to the group of oxides with a 2DEG at their surface. Our study widens the phase space to investigate strontium and barium doped CaTiO$_3$ and the interplay of ferroelectric properties with the 2DEG at oxide surfaces. This could open up new paths to tailor two-dimensional transport properties of these systems towards possible applications.