Band-Gap Reduction and Dopant Interaction in Epitaxial La,Cr Co-doped SrTiO3 Thin Films

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• 作者：Ryan B. Comes ; Peter V. Sushko ; Steve M. Heald ; Robert J. Colby ; Mark E. Bowden ; Scott A. Chambers
• 刊名：Chemistry of Materials
• 出版年：2014
• 出版时间：December 23, 2014
• 年：2014
• 卷：26
• 期：24
• 页码：7073-7082
• 全文大小：635K
• ISSN：1520-5002

文摘

We show that by co-doping SrTiO₃ (STO) epitaxial thin films with equal amounts of La and Cr, it is possible to produce films with an optical band gap 鈭?.9 eV lower than that of undoped STO. Sr_1鈥?i>xLa_xTi_1鈥?i>xCr_xO₃ thin films were deposited by molecular beam epitaxy and characterized using X-ray photoelectron spectroscopy and X-ray absorption near-edge spectroscopy to show that the Cr dopants are almost exclusively in the Cr³⁺ oxidation state. Extended X-ray absorption fine structure measurements and theoretical modeling suggest that it is thermodynamically preferred for La and Cr dopants to occupy nearest-neighbor A- and B-sites in the lattice. Transport measurements show that the material exhibits variable-range hopping conductivity with high resistivity. These results create new opportunities for the use of doped STO films in photovoltaic and photocatalytic applications.