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Valence-band orbital character of CdO: A synchrotron-radiation photoelectron spectroscopy and density functional theory study

DOI: 10.1103/PhysRevB.89.165305 DOI Help

Authors: J. J. Mudd (University of Warwick) , T.-l. Lee (Diamond Light Source) , V. Muñoz-sanjosé (Universitat de Valencia) , J. Zúñiga-pérez (Centre National de la Recherche Scientifique) , D. J. Payne (Imperial College London) , R. G. Egdell (University of Oxford) , C. F. Mcconville (University of Warwick)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Physical Review B , VOL 89 (16)

State: Published (Approved)
Published: April 2014
Diamond Proposal Number(s): 8441

Open Access Open Access

Abstract: N-type CdO is a transparent conducting oxide (TCO) which has promise in a number of areas including solar cell applications. In order to realize this potential a detailed knowledge of the electronic structure of the material is essential. In particular, standard density functional theory (DFT) methods struggle to accurately predict fundamental material properties such as the band gap. This is largely due to the underestimation of the Cd 4d binding energy, which results in a strong hybridization with the valence-band (VB) states. In order to test theoretical approaches, comparisons to experiment need to be made. Here, synchrotron-radiation photoelectron spectroscopy (SR-PES) measurements are presented, and comparison with three theoretical approaches are made. In particular the position of the Cd 4d state is measured with hard x-ray PES, and the orbital character of the VB is probed by photon energy dependent measurements. It is found that LDA + U using a theoretical U value of 2.34 eV is very successful in predicting the position of the Cd 4d state. The VB photon energy dependence reveals the O 2p photoionization cross section is underestimated at higher photon energies, and that an orbital contribution from Cd 5p is underestimated by all the DFT approaches.

Subject Areas: Materials, Physics

Instruments: I09-Surface and Interface Structural Analysis

Other Facilities: No

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