$\sqrt{2}$$\times$$\sqrt{2}R45^{\circ }$ surface reconstruction and electronic structure of BaSnO${}_3$ film

Abstract

We studied surface and electronic structures of barium stannate (BaSnO${}_3$) thin-film by low energy electron diffraction (LEED), and angle-resolved photoemission spectroscopy (ARPES) techniques. BaSnO${}_3$/Ba${}_{0.96}$La${}_{0.04}$SnO${}_3$/SrTiO${}_3$ (10 nm/100 nm/0.5 mm) samples were grown using pulsed-laser deposition (PLD) method and were \emph{ex-situ} transferred from PLD chamber to ultra-high vacuum (UHV) chambers for annealing, LEED and ARPES studies. UHV annealing starting from 300${}^{\circ }$C up to 550${}^{\circ }$C, followed by LEED and ARPES measurements show 1$\times$1 surfaces with non-dispersive energy-momentum bands. The 1$\times$1 surface reconstructs into a $\sqrt{2}$$\times$$\sqrt{2}R45^{\circ }$ one at the annealing temperature of 700${}^{\circ }$C where the ARPES data shows clear dispersive bands with valence band maximum located around 3.3 eV below Fermi level. While the $\sqrt{2}$$\times$$\sqrt{2}R45^{\circ }$ surface reconstruction is stable under further UHV annealing, it is reversed to 1$\times$1 surface by annealing the sample in 400 mTorr oxygen at 600${}^{\circ }$C. Another UHV annealing at 600${}^{\circ }$C followed by LEED and ARPES measurements, suggests that LEED $\sqrt{2}$$\times$$\sqrt{2}R45^{\circ }$ surface reconstruction and ARPES dispersive bands are reproduced. Our results provide a better picture of electronic structure of BaSnO${}_3$ surface and are suggestive of role of oxygen vacancies in the reversible $\sqrt{2}$$\times$$\sqrt{2}R45^{\circ }$ surface reconstruction.

7 pages, 4 figures, Journal