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1. Orbital-selective Band Hybridisation at the Charge Density Wave Transition in Monolayer TiTe$_2$

Author

Antonelli, T., Rahim, W., Watson, M. D., Rajan, A., Clark, O. J., Danilenko, A., Underwood, K., Markovic, I., Abarca-Morales, E., Kavanagh, S. R., Fevre, P., Bertran, F., Rossnagel, K., Scanlon, D. O., and King, P. D. C.

Subjects
Condensed Matter - Strongly Correlated Electrons
Abstract

An anomalous $(2\times2)$ charge density wave (CDW) phase emerges in monolayer 1T-TiTe$_2$ which is absent for the bulk compound, and whose origin is still poorly understood. Here, we investigate the electronic band structure evolution across the CDW transition using temperature-dependent angle-resolved photoemission spectroscopy. Our study reveals an orbital-selective band hybridisation between the backfolded conduction and valence bands occurring at the CDW phase transition, which in turn leads to a significant electronic energy gain, underpinning the CDW transition. For the bulk compound, we show how this energy gain is almost completely suppressed due to the three-dimensionality of the electronic band structure, including via a $k_z$-dependent band inversion which switches the orbital character of the valence states. Our study thus sheds new light on how control of the electronic dimensionalilty can be used to trigger the emergence of new collective states in 2D materials.

Published
2022
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2. Intrinsic point defects and the $n$- and $p$-type dopability of the narrow gap semiconductors GaSb and InSb

Author

Buckeridge, J., Veal, T. D., Catlow, C. R. A., and Scanlon, D. O.

Subjects
Condensed Matter - Materials Science
Abstract

The presence of defects in the narrow-gap semiconductors GaSb and InSb affects their dopability and hence applicability for a range of optoelectronic applications. Here, we report hybrid density functional theory based calculations of the properties of intrinsic point defects in the two systems, including spin orbit coupling effects, which influence strongly their band structures. With the hybrid DFT approach we adopt, we obtain excellent agreement between our calculated band dispersions, structural, elastic and vibrational properties and available measurements. We compute point defect formation energies in both systems, finding that antisite disorder tends to dominate, apart from in GaSb under certain conditions, where cation vacancies can form in significant concentrations. Calculated self-consistent Fermi energies and equilibrium carrier and defect concentrations confirm the intrinsic $n$- and $p$-type behaviour of both materials under anion-rich and anion-poor conditions. Moreover, by computing the compensating defect concentrations due to the presence of ionised donors and acceptors, we explain the observed dopability of GaSb and InSb.

Published
2019
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3. Narrow-band anisotropic electronic structure of ReS$_2$

Author

Biswas, D., Ganose, A. M., Yano, R., Riley, J. M., Bawden, L., Clark, O. J., Feng, J., Collins-Mcintyre, L., Meevasana, W., Kim, T. K., Hoesch, M., Rault, J. E., Sasagawa, T., Scanlon, D. O., and King, P. D. C.

Subjects
Condensed Matter - Materials Science
Abstract

We have used angle resolved photoemission spectroscopy to investigate the band structure of ReS$_2$, a transition-metal dichalcogenide semiconductor with a distorted 1T crystal structure. We find a large number of narrow valence bands, which we attribute to the combined influence of the structural distortion and spin-orbit coupling. We further image how this leads to a strong in-plane anisotropy of the electronic structure, with quasi-one-dimensional bands reflecting predominant hopping along zig-zag Re chains. We find that this does not persist up to the top of the valence band, where a more three-dimensional character is recovered with the fundamental band gap located away from the Brillouin zone centre along $k_z$. These experiments are in good agreement with our density-functional theory calculations, shedding new light on the bulk electronic structure of ReS$_2$, and how it can be expected to evolve when thinned to a single layer.

Published
2017
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4. Antiferromagnetism at T > 500 K in the Layered Hexagonal Ruthenate SrRu2O6

Author

Hiley, C. I., Scanlon, D. O., Sokol, A. A., Woodley, S. M., Ganose, A. M., Sangiao, S., De Teresa, J. M., Manuel, P., Khalyavin, D. D., Walker, M., Lees, M. R., and Walton, R. I.

Subjects
Condensed Matter - Strongly Correlated Electrons
Abstract

We report an experimental and computational study of magnetic and electronic properties of the layered Ru(V) oxide SrRu2O6 (hexagonal, P-3 1m), which shows antiferromagnetic order with a N\'eel temperature of 563(2) K, among the highest for 4d oxides. Magnetic order occurs both within edge-shared octahedral sheets and between layers and is accompanied by anisotropic thermal expansivity that implies strong magnetoelastic coupling of Ru(V) centers. Electrical transport measurements using focused ion beam induced deposited contacts on a micron-scale crystallite as a function of temperature show p-type semiconductivity. The calculated electronic structure using hybrid density functional theory successfully accounts for the experimentally observed magnetic and electronic structure and Monte Carlo simulations reveals how strong intralayer as well as weaker interlayer interactions are a defining feature of the high temperature magnetic order in the material., Comment: Physical Review B 2015 accepted for publication

Published
2015
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5. Determination of the nitrogen vacancy as a shallow compensating center in GaN doped with divalent metals

Author

Buckeridge, J., Catlow, C. R. A., Scanlon, D. O., Keal, T. W., Sherwood, P., Miskufova, M., Walsh, A., Woodley, S. M., and Sokol, A. A.

Subjects
Condensed Matter - Materials Science
Abstract

We report accurate energetics of defects introduced in GaN on doping with divalent metals, focussing on the technologically important case of Mg doping, using a model which takes into consideration both the effect of hole localisation and dipolar polarisation of the host material, and includes a well-defined reference level. Defect formation and ionisation energies show that divalent dopants are counterbalanced in GaN by nitrogen vacancies and not by holes, which explains both the difficulty in achieving p-type conductivity in GaN and the associated major spectroscopic features, including the ubiquitous 3.46 eV photoluminescence line, a characteristic of all lightly divalent metal-doped GaN materials that has also been shown to occur in pure GaN samples. Our results give a comprehensive explanation for the observed behaviour of GaN doped with low concentrations of divalent metals in good agreement with relevant experiment., Comment: 6 pages, 3 figures

Published
2014
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6. Controlling bulk conductivity in topological insulators: Key role of anti-site defects

Author

Scanlon, D. O., King, P. D. C., Singh, R. P., de la Torre, A., Walker, S. McKeown, Balakrishnan, G., Baumberger, F., and Catlow, C. R. A.

Subjects
Condensed Matter - Materials Science
Abstract

The binary Bi-chalchogenides, Bi2Ch3, are widely regarded as model examples of a recently discovered new form of quantum matter, the three-dimensional topological insulator (TI) [1-4]. These compounds host a single spin-helical surface state which is guaranteed to be metallic due to time reversal symmetry, and should be ideal materials with which to realize spintronic and quantum computing applications of TIs [5]. However, the vast majority of such compounds synthesized to date are not insulators at all, but rather have detrimental metallic bulk conductivity [2, 3]. This is generally accepted to result from unintentional doping by defects, although the nature of the defects responsible across different compounds, as well as strategies to minimize their detrimental role, are surprisingly poorly understood. Here, we present a comprehensive survey of the defect landscape of Bi-chalchogenide TIs from first-principles calculations. We find that fundamental differences in the energetics of native defect formation in Te- and Se-containing TIs enables precise control of the conductivity across the ternary Bi-Te-Se alloy system. From a systematic angle-resolved photoemission (ARPES) investigation of such ternary alloys, combined with bulk transport measurements, we demonstrate that this method can be utilized to achieve true topological insulators, with only a single Dirac cone surface state intersecting the chemical potential. Our microscopic calculations reveal the key role of anti-site defects for achieving this, and predict optimal growth conditions to realize maximally-resistive ternary TIs., Comment: 6 pages, 4 figures, 1 table

Published
2012
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13. Enhanced Photoresponse of FeS2 Films: The Role of Marcasite–Pyrite Phase Junctions

Author

Wu, Longfei, Dzade, N.Y., Gao, L., Scanlon, D. O., Özturk, Zafer, Hollingsworth, N., Weckhuysen, B.M., Hensen, E. J. M., de Leeuw, Nora H., Hofmann , J. P., Geochemistry of Earth materials, Geochemistry, and Sub Inorganic Chemistry and Catalysis

Subjects
Iron pyrite, Photovoltaic, Solar Cells
Abstract

The beneficial role of marcasite in iron sulfide-based photo-electrochemical applications is reported for the first time. A spectacular improvement of the photoresponse observed experimentally for mixed pyrite/marcasite-FeS2 films can be ascribed to the presence of p/m phase junctions at the interface. Density functional theory calculations show that the band alignment at the phase boundary contributes to enhanced charge separation and transfer across the interface.

Published
2016

14. Photoelectrochemistry: Enhanced Photoresponse of FeS2 Films: The Role of Marcasite–Pyrite Phase Junctions (Adv. Mater. 43/2016, Back Cover)

Author

Wu, Longfei, Dzade, N.Y., Gao, L., Scanlon, D. O., Öztürk, Z., Hollingsworth, N., Weckhuysen, B.M., Hensen, E. J. M., de Leeuw, Nora H., Hofmann, J. P., Geochemistry, Sub Inorganic Chemistry and Catalysis, and Geochemistry of Earth materials

Subjects
Photocurrent, Materials science, business.industry, Charge separation, Mechanical Engineering, phase junctions, Photoelectrochemistry, Nanotechnology, charge separation, engineering.material, Polymer solar cell, pyrite, marcasite, Mechanics of Materials, Phase (matter), band alignment, engineering, Optoelectronics, Marcasite, General Materials Science, Pyrite, Thin film, business
Abstract

The beneficial role of marcasite in pyrite thin films for photoelectrochemical applications is reported by J. P. Hofmann and co-workers on page 9602. A bulk heterojunction with staggered band alignment at the pyrite–marcasite interface enhances charge-carrier separation and leads to a dramatic increase of photocurrent in the FeS2 films.

Published
2016
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16. Photoelectrochemistry: Enhanced Photoresponse of FeS2 Films: The Role of Marcasite–Pyrite Phase Junctions (Adv. Mater. 43/2016, Back Cover)

Author

Geochemistry, Sub Inorganic Chemistry and Catalysis, Geochemistry of Earth materials, Wu, Longfei, Dzade, N.Y., Gao, L., Scanlon, D. O., Öztürk, Z., Hollingsworth, N., Weckhuysen, B.M., Hensen, E. J. M., de Leeuw, Nora H., Hofmann , J. P., Geochemistry, Sub Inorganic Chemistry and Catalysis, Geochemistry of Earth materials, Wu, Longfei, Dzade, N.Y., Gao, L., Scanlon, D. O., Öztürk, Z., Hollingsworth, N., Weckhuysen, B.M., Hensen, E. J. M., de Leeuw, Nora H., and Hofmann , J. P.

Published
2016

17. Enhanced Photoresponse of FeS2 Films: The Role of Marcasite–Pyrite Phase Junctions

Author

Geochemistry of Earth materials, Geochemistry, Sub Inorganic Chemistry and Catalysis, Wu, Longfei, Dzade, N.Y., Gao, L., Scanlon, D. O., Özturk, Zafer, Hollingsworth, N., Weckhuysen, B.M., Hensen, E. J. M., de Leeuw, Nora H., Hofmann , J. P., Geochemistry of Earth materials, Geochemistry, Sub Inorganic Chemistry and Catalysis, Wu, Longfei, Dzade, N.Y., Gao, L., Scanlon, D. O., Özturk, Zafer, Hollingsworth, N., Weckhuysen, B.M., Hensen, E. J. M., de Leeuw, Nora H., and Hofmann , J. P.

Published
2016

19. Stability of the M2 phase of vanadium dioxide induced by coherent epitaxial strain

Author

Quackenbush, N. F., primary, Paik, H., additional, Wahila, M. J., additional, Sallis, S., additional, Holtz, M. E., additional, Huang, X., additional, Ganose, A., additional, Morgan, B. J., additional, Scanlon, D. O., additional, Gu, Y., additional, Xue, F., additional, Chen, L.-Q., additional, Sterbinsky, G. E., additional, Schlueter, C., additional, Lee, T.-L., additional, Woicik, J. C., additional, Guo, J.-H., additional, Brock, J. D., additional, Muller, D. A., additional, Arena, D. A., additional, Schlom, D. G., additional, and Piper, L. F. J., additional

Published
2016
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20. Direct Observation of Electrostatically Driven Band Gap Renormalization in a Degenerate Perovskite Transparent Conducting Oxide

Author

Lebens-Higgins, Z., primary, Scanlon, D. O., additional, Paik, H., additional, Sallis, S., additional, Nie, Y., additional, Uchida, M., additional, Quackenbush, N. F., additional, Wahila, M. J., additional, Sterbinsky, G. E., additional, Arena, Dario A., additional, Woicik, J. C., additional, Schlom, D. G., additional, and Piper, L. F. J., additional

Published
2016
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22. Interfacial Effects in ε-LixVOPO4 and Evolution of the Electronic Structure

Author

Quackenbush, N. F., primary, Wangoh, L., additional, Scanlon, D. O., additional, Zhang, R., additional, Chung, Y., additional, Chen, Z., additional, Wen, B., additional, Lin, Y., additional, Woicik, J. C., additional, Chernova, N. A., additional, Ong, S. P., additional, Whittingham, M.S., additional, and Piper, L. F. J., additional

Published
2015
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24. Antiferromagnetism atT>500Kin the layered hexagonal ruthenateSrRu2O6

Author

Hiley, C. I., primary, Scanlon, D. O., additional, Sokol, A. A., additional, Woodley, S. M., additional, Ganose, A. M., additional, Sangiao, S., additional, De Teresa, J. M., additional, Manuel, P., additional, Khalyavin, D. D., additional, Walker, M., additional, Lees, M. R., additional, and Walton, R. I., additional

Published
2015
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25. Buckeridgeet al.Reply

Author

Buckeridge, J., primary, Catlow, C. R. A., additional, Scanlon, D. O., additional, Keal, T. W., additional, Sherwood, P., additional, Miskufova, M., additional, Walsh, A., additional, Woodley, S. M., additional, and Sokol, A. A., additional

Published
2015
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28. Understanding the Electronic Structure ofIrO2Using Hard-X-ray Photoelectron Spectroscopy and Density-Functional Theory

Author

Kahk, J. M., primary, Poll, C. G., additional, Oropeza, F. E., additional, Ablett, J. M., additional, Céolin, D., additional, Rueff, J-P., additional, Agrestini, S., additional, Utsumi, Y., additional, Tsuei, K. D., additional, Liao, Y. F., additional, Borgatti, F., additional, Panaccione, G., additional, Regoutz, A., additional, Egdell, R. G., additional, Morgan, B. J., additional, Scanlon, D. O., additional, and Payne, D. J., additional

Published
2014
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32. Growth and properties of GaSbBi alloys

Author

Rajpalke, M. K., primary, Linhart, W. M., additional, Birkett, M., additional, Yu, K. M., additional, Scanlon, D. O., additional, Buckeridge, J., additional, Jones, T. S., additional, Ashwin, M. J., additional, and Veal, T. D., additional

Published
2013
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33. Growth, disorder, and physical properties of ZnSnN2

Author

Feldberg, N., primary, Aldous, J. D., additional, Linhart, W. M., additional, Phillips, L. J., additional, Durose, K., additional, Stampe, P. A., additional, Kennedy, R. J., additional, Scanlon, D. O., additional, Vardar, G., additional, Field, R. L., additional, Jen, T. Y., additional, Goldman, R. S., additional, Veal, T. D., additional, and Durbin, S. M., additional

Published
2013
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35. Origin of the Bipolar Doping Behavior of SnO from X-ray Spectroscopy and Density Functional Theory

Author

Quackenbush, N. F., primary, Allen, J. P., additional, Scanlon, D. O., additional, Sallis, S., additional, Hewlett, J. A., additional, Nandur, A. S., additional, Chen, B., additional, Smith, K. E., additional, Weiland, C., additional, Fischer, D. A., additional, Woicik, J. C., additional, White, B. E., additional, Watson, G. W., additional, and Piper, L. F. J., additional

Published
2013
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37. Elucidating the Nature of Pseudo Jahn–Teller Distortions in LixMnPO4: Combining Density Functional Theory with Soft and Hard X-ray Spectroscopy

Author

Piper, L. F. J., primary, Quackenbush, N. F., additional, Sallis, S., additional, Scanlon, D. O., additional, Watson, G. W., additional, Nam, K.-W., additional, Yang, X.-Q., additional, Smith, K. E., additional, Omenya, F., additional, Chernova, N. A., additional, and Whittingham, M. S., additional

Published
2013
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39. Band gap reduction in InNxSb1-x alloys: Optical absorption, k · P modeling, and density functional theory.

Author

Linhart, W. M., Rajpalke, M. K., Buckeridge, J., Murgatroyd, P. A. E., Bomphrey, J. J., Alaria, J., Catlow, C. R. A., Scanlon, D. O., Ashwin, M. J., and Veal, T. D.

Subjects
BAND gaps, INDIUM antimonide, LIGHT absorption, DENSITY functional theory, THIN films, NITROGEN
Abstract

Using infrared absorption, the room temperature band gap of InSb is found to reduce from 174 (7.1 μm) to 85 meV (14.6 μm) upon incorporation of up to 1.13% N, a reduction of ∼79 meV/%N. The experimentally observed band gap reduction in molecular-beam epitaxial InNSb thin films is reproduced by a five band k · P band anticrossing model incorporating a nitrogen level, EN, 0.75 eV above the valence band maximum of the host InSb and an interaction coupling matrix element between the host conduction band and the N level of β = 1.80 eV. This observation is consistent with the presented results from hybrid density functional theory. [ABSTRACT FROM AUTHOR]

Published
2016
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42. Comparative study of bandwidths in copper delafossites from x-ray emission spectroscopy

Author

Shin, D., primary, Foord, J. S., additional, Payne, D. J., additional, Arnold, T., additional, Aston, D. J., additional, Egdell, R. G., additional, Godinho, K. G., additional, Scanlon, D. O., additional, Morgan, B. J., additional, Watson, G. W., additional, Mugnier, E., additional, Yaicle, C., additional, Rougier, A., additional, Colakerol, L., additional, Glans, P. A., additional, Piper, L. F. J., additional, and Smith, K. E., additional

Published
2009
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44. X-ray spectroscopic study of the electronic structure ofCuCrO2

Author

Arnold, T., primary, Payne, D. J., additional, Bourlange, A., additional, Hu, J. P., additional, Egdell, R. G., additional, Piper, L. F. J., additional, Colakerol, L., additional, De Masi, A., additional, Glans, P.-A., additional, Learmonth, T., additional, Smith, K. E., additional, Guo, J., additional, Scanlon, D. O., additional, Walsh, A., additional, Morgan, B. J., additional, and Watson, G. W., additional

Published
2009
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48. Scalable route to CH3NH3PbI3 perovskite thin films by aerosol assisted chemical vapour deposition.

Author

Bhachu, D. S., Scanlon, D. O., Saban, E. J., Bronstein, H., Parkin, I. P., Carmalt, C. J., and Palgrave, R. G.

Abstract

Methyl-ammonium lead iodide is the archetypal perovskite solar cell material. Phase pure, compositionally uniform methyl-ammonium lead iodide thin films on large glass substrates were deposited using ambient pressure aerosol assisted chemical vapour deposition. This opens up a route to efficient scale up of hybrid perovskite film growth towards industrial deployment. [ABSTRACT FROM AUTHOR]

Published
2015
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50. Intrinsic point defects and the n - and p -type dopability of the narrow gap semiconductors GaSb and InSb

Author

Buckeridge, J., Veal, T. D., Catlow, C. R. A., and Scanlon, D. O.

Subjects
Condensed Matter - Materials Science, Condensed Matter::Materials Science, Materials Science (cond-mat.mtrl-sci), FOS: Physical sciences, Physics::Chemical Physics
Abstract

The presence of defects in the narrow gap semiconductors GaSb and InSb affects their dopability and hence applicability for a range of optoelectronic applications. Here, we report hybrid density functional theory (DFT)-based calculations of the properties of intrinsic point defects in the two systems, including spin-orbit coupling effects, which influence strongly their band structures. With the hybrid DFT approach adopted, we obtain excellent agreement between our calculated band dispersions and structural, elastic, and vibrational properties and available measurements. We compute point defect formation energies in both systems, finding that antisite disorder tends to dominate, apart from in GaSb under certain conditions, where cation vacancies can form in significant concentrations. Calculated self-consistent Fermi energies and equilibrium carrier and defect concentrations confirm the intrinsic n- and p-type behavior of both materials under anion-rich and anion-poor conditions. Moreover, by computing the compensating defect concentrations due to the presence of ionized donors and acceptors, we explain the observed dopability of GaSb and InSb.

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