Observation of a two-dimensional electron gas at CaTiO3 film surfaces

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 CaTiO3, grown by pulsed laser deposition, by means of angular-resolved photoelectron spectroscopy. The films show a c(4 × 2) surface reconstruction after the growth that is reduced to a p(2 × 2) reconstruction under UV-light. At the CaTiO3 film surface, a two-dimensional electron gas (2DEG) is found with an occupied band width of 400 meV. With our findings CaTiO3 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 CaTiO3 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.