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Band edge evolution of transparent Zn M 2 I I I O 4 ( M I I I = Co , Rh, Ir) spinels

DOI: 10.1103/PhysRevB.100.085126 DOI Help

Authors: Matthew Wahila (Binghamton University) , Zachary W. Lebens-higgins (Binghamton University) , Adam J. Jackson (University College London) , David O. Scanlon (University College London) , Tien-lin Lee (Diamond Light Source) , Jiaye Zhang (Xiamen University) , Kelvin H. L. Zhang (Xiamen University; University of Cambridge) , Louis F. J. Piper (Binghamton University)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Physical Review B , VOL 100

State: Published (Approved)
Published: August 2019
Diamond Proposal Number(s): 16005

Abstract: Zn M I I I 2 O 4 ( M I I I = Co , Rh, Ir) spinels have been recently identified as promising p -type semiconductors for transparent electronics. However, discrepancies exist in the literature regarding their fundamental optoelectronic properties. In this paper, the electronic structures of these spinels are directly investigated using soft/hard x-ray photoelectron and x-ray absorption spectroscopies in conjunction with density functional theory calculations. In contrast to previous results, ZnCo 2 O 4 is found to have a small electronic band gap with forbidden optical transitions between the true band edges, allowing for both bipolar doping and high optical transparency. Furthermore, increased d − d splitting combined with a concomitant lowering of Zn s / p conduction states is found to result in a ZnCo 2 O 4 ( ZCO ) < ZnRh 2 O 4 ( ZRO ) ≈ ZnIr 2 O 4 ( ZIO ) band gap trend, finally resolving long-standing discrepancies in the literature.

Journal Keywords: Band gap; Composition; Density of states; Electrical conductivity; Electronic structure; Optoelectronics; Oxides

Subject Areas: Materials, Physics

Instruments: I09-Surface and Interface Structural Analysis