Gap modulation in MCu[Q1−xQ′x]F (M=Ba, Sr; Q, Q′=S, Se, Te) and related materials |
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Authors: | Cheol-Hee ParkDouglas A. Keszler Hiroshi YanagiJanet Tate |
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Affiliation: | a Department of Chemistry, Oregon State University, Corvallis, OR 97331, USA b Department of Physics, Oregon State University, Corvallis, OR 97331, USA |
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Abstract: | BaCuQF (Q=S, Se, Te) materials exhibit band gaps that allow transmission of much of the visible spectrum. BaCuSF is transparent in thin-film form with a band gap of 3.1 eV. Band gap estimates for powders of the solid solution series BaCuS1−xSexF were obtained from wavelength-dependent diffuse-reflectance measurements using an integrating sphere. The band gap can be tuned by the substitution of Se for S to 2.9 eV for BaCuSeF. The decrease scales almost linearly with the increase in the volume of the tetragonal unit cell, which is determined primarily by the expansion of the a lattice parameter; the overall volume increase is 7.0% from x=0 to 1. Further reduction of the band gap is observed in BaCuSe1−xTexF solid solutions, where a unit cell volume increase of 5.5% produces a band gap of 2.7 eV in BaCuSe0.5Te0.5F. Powders and films of BaCuSF exhibit strong red luminescence under ultraviolet excitation, which is suppressed by K doping. Additional tuning of band gap and electrical properties (the materials are p-type conductors) can be achieved by replacing Ba with Sr. |
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Keywords: | Transparent conductors Chalcogenide fluorides Band gap tuning Luminescence |
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