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تسجيل مستخدم جديد$sqrt{2}$$times$$sqrt{2}R45^circ$ surface reconstruction and electronic structure of BaSnO$_3$ film
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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.
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