Electronic and optical properties of doped 
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 by many-body perturbation theory

Atambo, Michael O; Varsano, Daniele; Ferretti, Andrea; Ataei, S. Samaneh; Caldas, M. J.; Molinari, Elisa; Selloni, Annabella

doi:10.1103/physrevmaterials.3.045401

Cited by 29 publications

(36 citation statements)

References 61 publications

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“…First-principles calculations have been reported on r-TiO 2 in order to predict the absorption related to defects in the material. The corresponding reports suggest that Nb Ti , H i , Ti i and V O all give rise to optical absorption in the range between 0.6 eV and 2.0 eV [224,243,251,[281][282][283]. The similarities seen for a wide range of different defects is usually ascribed to the formation of polarons [251,283].…”

Section: Influence Of Defects On the Optical Propertiesmentioning

confidence: 98%

Ti- and Fe-related charge transition levels in β−Ga2O3

Zimmermann

Frodason

Barnard

et al. 2020

Applied Physics Letters

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This thesis would not have been possible without the support of many people, and I am eternally grateful for all the support. I hope to see some of you again in the future! The main objective of my PhD project was to study defects in semiconducting oxides within the research project FOXHOUND headed by Prof. Lasse Vines, my main supervisor. I am grateful to Lasse for the opportunity to work on this topic. I have learned much more than I imagined I would when I started. Lasse, you have been a patient and competent supervisor who always took time to answer endless streams of questions. Prof. Truls Norby and Assoc. Prof. Anette Eleonora Gunnaes were co-advisors for my PhD project. I am grateful to Truls for introducing me to the chemist's view on defects and his group FASE/ELCHEM. I am truly sad that I did not get to collaborate more with Anette. I also want to thank Prof. Eduard Monakhov and the late Prof. Bengt Gunnar Svensson. Both were valuable unofficial advisers on my PhD, and helped moving my work along. Most of my work was carried out within the semiconductor physics group at the University of Oslo (LENS), and I would like to thank of all its current and former members for contributing to my work in many ways. There are some people who deserve special thanks. First of all, I am grateful to my long-term office mates Torunn, Sigbjørn and Josef for sharing many conversations and being there for each other. Secondly, I am particularly grateful to all my close collaborators at LENS, and especially Julie, Philip, Ymir, Vegard R., Vegard O., Viktor and Espen. I also want to thank our engineers (Micke, Halvor, Christoph and Viktor) and administrative staff (Marit, Heine and Kristin) for keeping things running! Also, thanks to Ilia, Robert, Vegard R. and Jon for taking care of the needs of the E-Lab and the Online-Setup. I was a co-supervisor for two master students: Vegard R. and Espen. I hope both of them learned something from me, because I did definitely learn from them. I am particularly grateful to Vegard R. for being a large part in building the steady-state photo-capacitance setup used in this work. I also would like to thank all my co-authors from outside of Oslo: Frank from Dresden, Willem, Walter and Danie from Pretoria, Klaus and Zbigniew from Berlin, Antti from Aalto and Joel from California. Special thanks to Willem, Walter and Danie for hosting me in Pretoria and showing me around. Last but not least, I would like to thank my family and my friends for their support!

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Section: Influence Of Defects On the Optical Propertiesmentioning

confidence: 98%

Ti- and Fe-related charge transition levels in β−Ga2O3

Zimmermann

Frodason

Barnard

et al. 2020

Applied Physics Letters

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“…Atomic defects on metal oxides, such as oxygen vacancies and interstitials have received most interest, and are often considered to increase surface activity [5][6][7][8][9][10][11][12][13][14][15]. For example, on the surfaces of TiO 2a key material for photocatalysis and photovoltaics and also a widely studied model system [1,[16][17][18][19] -surface oxygen vacancies are active sites for water dissociation [20], with implications for water splitting as a potential means to produce abundant and clean hydrogen fuel [21].…”

mentioning

confidence: 99%

Small polarons and the Janus nature of TiO2 (110)

et al. 2020

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Polarons are ubiquitous in many semiconductors and have been linked with conductivity and optical response of materials for photovoltaics and heterogeneous catalysis, yet how surface polarons influence adsorption remains unclear. Here, by modelling the surface of rutile titania using density functional theory, we reveal the effect of small surface polarons on water adsorption, dissociation, and hydrogen bonding. On the one hand the presence of such polarons significantly suppresses dissociation of water molecules that are bonded directly to polaronic sites. On the other hand, polarons facilitate water dissociation at certain non-polaronic sites. Furthermore, polarons strengthen hydrogen bonds, which in turn affects water dissociation in hydrogen bonded overlayer structures.This study reveals that polarons at the rutile surface have complex, multi-faceted, effects on water adsorption, dissociation and hydrogen bonding, highlighting the importance of polarons on water structure and dynamics on such surfaces. We expect that many of the physical properties of surface polarons identified here will apply more generally to surfaces and interfaces that can host small polarons, beyond titania.

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“…Recent first-principles calculations by Atambo al. 46 predict absorption features at 0.33 and 0.60 eV in H-doped and at 0.35 and 0.93 eV in Nb-doped rutile TiO 2 , which they assign to transitions from donor-bound electron polarons to the conduction band minimum. We observe that the maxima of ω 2 and ω 1 occur (at LT) near 3300 cm −1 (0.41 eV) and 6600 cm −1 (0.82 eV) in H-doped and near 3700 cm −1 (0.46 eV) and 7500 cm −1 (0.93 eV) in Nb-doped samples.…”

Section: Discussionmentioning

confidence: 95%

“…The small polaron model in rutile TiO 2 has been supported by other experimental techniques, including muon spin rotation spectroscopy (μSR), 43,44 and by first principles calculations. 22,23,[45][46][47][48] Despite these insights, the nature of the charge transport (free carrier vs impurity band vs polaron related) remains unanswered. Recent first-principles calculations 23,45 suggest that small polarons and delocalized electrons can coexist in rutile TiO 2 , with a small energy difference (<∼0.1 eV) between the two states, and there is experimental evidence for this coexistence in reduced TiO 2 nanoparticles.…”

Section: Introductionmentioning

confidence: 99%

Donors and polaronic absorption in rutile TiO2 single crystals

Weiser

Zimmermann

Bonkerud

et al. 2020

Journal of Applied Physics

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We have used a combination of optical absorption and electrical conductivity measurements to study the effect of the main donor on small polarons in rutile TiO 2 single crystals rendered n-type conductive by hydrogenation or doping with Nb. The electrical conductivity measured at 295 K for hydrogenated samples shows a clear correlation with the interstitial hydrogen (H i ) concentration, which is consistent with reports that H i is the main shallow donor in rutile TiO 2 . Conductive samples exhibit two distinct optical absorption bands in the IR spectral region, at ω 1 = 6500 cm −1 (∼0.8 eV) and ω 2 = 3100 cm −1 (∼0.4 eV), which are present in both hydrogen-rich and Nb-doped samples. The intensities of the absorption bands are proportional to the electrical conductivity, and they exhibit an Arrhenius-like temperature dependence for temperatures between 25-50 K and 50-100 K for H-doped and Nb-doped samples, respectively. The thermal activation energies (E A s) for the absorption bands depend strongly on the main donor: ω 2 exhibits E A (H) and E A (Nb) of ∼4 and ∼10 meV, respectively, whereas ω 1 shows E A (H) and E A (Nb) of ∼1 and ∼2 meV, respectively. The combination of temperature-dependent data for the optical absorption bands and interstitial deuterium (D i )-small polaron vibrational lines support a model where the thermal activation is associated with the reconfiguration of small polarons involving Ti sites far away from the donor. The thermal activation of the optical absorption bands gives us insight into the dynamics of donor-dependent small polaron reconfiguration in rutile TiO 2 .

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Electronic and optical properties of doped TiO2 by many-body perturbation theory

Cited by 29 publications

References 61 publications

Ti- and Fe-related charge transition levels in β−Ga2O3

Ti- and Fe-related charge transition levels in β−Ga2O3

Small polarons and the Janus nature of TiO2 (110)

Donors and polaronic absorption in rutile TiO2 single crystals

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