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Butorin, Sergei
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Publications (10 of 51) Show all publications
Phuyal, D., Safdari, M., Pazoki, M., Liu, P., Philippe, B., Kvashnina, K. O., . . . Gardner, J. (2018). Electronic Structure of Two-Dimensional Lead(II) Iodide Perovskites: An Experimental and Theoretical Study. Chemistry of Materials, 30(15), 4959-4967
Open this publication in new window or tab >>Electronic Structure of Two-Dimensional Lead(II) Iodide Perovskites: An Experimental and Theoretical Study
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2018 (English)In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 30, no 15, p. 4959-4967Article in journal (Refereed) Published
Abstract [en]

Layered two-dimensional (2D) hybrid organic-inorganic perovskites (HOP) are promising materials for light-harvesting applications because of their chemical stability, wide flexibility in composition and dimensionality, and increases in photovoltaic power conversion efficiencies. Three 2D lead iodide perovskites were studied through various X-ray spectroscopic techniques to derive detailed electronic structures and band energetics profiles at a titania interface. Core-level and valence band photoelectron spectra of HOP were analyzed to resolve the electronic structure changes due to the reduced dimensionality of inorganic layers. The results show orbital narrowing when comparing the HOP, the layered precursor PbI2, and the conventional 3D (CH3NH3)PbI3 such that different localizations of band edge states and narrow band states are unambiguously due to the decrease in dimensionality of the layered HOPs. Support from density functional theory calculations provide further details on the interaction and band gap variations of the electronic structure. We observed an interlayer distance dependent dispersion in the near band edge electronic states. The results show how tuning the interlayer distance between the inorganic layers affects the electronic properties and provides important design principles for control of the interlayer charge transport properties, such as the change in effective charge masses as a function of the organic cation length. The results of these findings can be used to tune layered materials for optimal functionality and new applications.

National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-361922 (URN)10.1021/acs.chemmater.8b00909 (DOI)000442186500014 ()
Funder
StandUpSwedish Energy AgencySwedish Research CouncilKnut and Alice Wallenberg Foundation
Note

De två första författarna delar förstaförfattarskapet.

Available from: 2018-09-27 Created: 2018-09-27 Last updated: 2018-10-23Bibliographically approved
Bes, R., Kvashnina, K., Rossberg, A., Dottavio, G., Desgranges, L., Pontillon, Y., . . . Martin, P. (2018). New insight in the uranium valence state determination in UyNd1-yO2 +/- x. Journal of Nuclear Materials, 507, 145-150
Open this publication in new window or tab >>New insight in the uranium valence state determination in UyNd1-yO2 +/- x
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2018 (English)In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 507, p. 145-150Article in journal (Refereed) Published
Abstract [en]

The charge compensation mechanisms in UyNd1-yO2 +/- x, and its consequence on the overall O stoichiometry (or O/M ratio where M = Nd + U) have been studied through the uranium valence state mixture evolution as a function of Nd content up to y = 0.62 by means of high energy resolution fluorescence detection X-ray absorption spectroscopy (HERFD-XAS) at the U M-4-edge. Our results clearly demonstrate the formation of U5+ at low Nd content (y < 0.15). Upon increasing the Nd content, oxygen vacancies and the formation of U6+ appear as competing mechanisms for intermediate Nd concentrations, leading to the co-existence of U4+/U5+/U6+ mixed valence and an overall hypostoichiometry (O/M < 2.00). Finally, the formation of U6+ associated with strongly distorted U local environment is observed for high Nd concentrations (y = 0.62), leading to an overall hyperstoichiometry (O/M < 2.00).

Place, publisher, year, edition, pages
ELSEVIER SCIENCE BV, 2018
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-361029 (URN)10.1016/j.jnucmat.2018.04.046 (DOI)000438019800017 ()
Funder
Swedish Research Council, 2017-06465
Available from: 2018-09-20 Created: 2018-09-20 Last updated: 2018-09-20Bibliographically approved
Phuyal, D., Jain, S. M., Philippe, B., Johansson, M. B., Pazoki, M., Kullgren, J., . . . Rensmo, H. (2018). The electronic structure and band interface of cesium bismuth iodide on a titania heterostructure using hard X-ray spectroscopy. Journal of Materials Chemistry A, 6(20), 9498-9505
Open this publication in new window or tab >>The electronic structure and band interface of cesium bismuth iodide on a titania heterostructure using hard X-ray spectroscopy
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2018 (English)In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 6, no 20, p. 9498-9505Article in journal (Refereed) Published
Abstract [en]

Bismuth halide compounds as a non-toxic alternative are increasingly investigated because of their potential in optoelectronic devices and their rich structural chemistry. Hard X-ray spectroscopy was applied to the ternary bismuth halide Cs3Bi2I9 and its related precursors BiI3 and CsI to understand its electronic structure at an atomic level. We specifically investigated the core levels and valence band using X-ray photoemission spectroscopy (PES), high-resolution X-ray absorption (HERFD-XAS), and resonant inelastic X-ray scattering (RIXS) to get insight into the chemistry and the band edge properties of the two bismuth compounds. Using these element specific X-ray techniques, our experimental electronic structures show that the primary differences between the two bismuth samples are the position of the iodine states in the valence and conduction bands and the degree of hybridization with bismuth lone pair (6s(2)) states. The crystal structure of the two layered quasi-perovskite compounds plays a minor role in modifying the overall electronic structure, with variations in bismuth lone pair states and iodine band edge states. Density Functional Theory (DFT) calculations are used to compare with experimental data. The results demonstrate the effectiveness of hard X-ray spectroscopies to identify element specific bulk electronic structures and their use in optoelectronic devices.

National Category
Materials Chemistry Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-357561 (URN)10.1039/c8ta00947c (DOI)000433427300020 ()
Funder
Swedish Research Council, 2014-6019Swedish Research Council, 2016-4524Swedish Energy Agency, P43549-1Swedish Foundation for Strategic Research , 15-0130Wallenberg Foundations, 2012.0031StandUp
Available from: 2018-08-20 Created: 2018-08-20 Last updated: 2018-08-20Bibliographically approved
Kvashnina, K. O., Kowalski, P. M., Butorin, S., Leinders, G., Pakarinen, J., Bes, R., . . . Verwerft, M. (2018). Trends in the valence band electronic structures of mixed uranium oxides. Chemical Communications, 54(70), 9757-9760
Open this publication in new window or tab >>Trends in the valence band electronic structures of mixed uranium oxides
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2018 (English)In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 54, no 70, p. 9757-9760Article in journal (Refereed) Published
Abstract [en]

The valence band electronic structures of mixed uranium oxides (UO2 , U4O9 , U3O7, U3O8 , and beta-UO3) have been studied using the resonant inelastic X-ray scattering (RIXS) technique at the U M-5 edge and computational methods. We show here that the RIXS technique and recorded U 5f-O 2p charge transfer excitations can be used to test the validity of theoretical approximations.

Place, publisher, year, edition, pages
ROYAL SOC CHEMISTRY, 2018
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-362100 (URN)10.1039/c8cc05464a (DOI)000442872000010 ()30109321 (PubMedID)
Available from: 2018-10-01 Created: 2018-10-01 Last updated: 2018-10-01Bibliographically approved
Butorin, S. M. M., Kvashnina, K. O., Prieur, D., Rivenet, M. & Martin, P. M. (2017). Characteristics of chemical bonding of pentavalent uranium in La-doped UO2. Chemical Communications, 53(1), 115-118
Open this publication in new window or tab >>Characteristics of chemical bonding of pentavalent uranium in La-doped UO2
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2017 (English)In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 53, no 1, p. 115-118Article in journal (Refereed) Published
Abstract [en]

The effect of La doping on the electronic structure of U in UO2 was studied using an advanced technique, namely, X-ray absorption spectroscopy (XAS) in the high-energy-resolution fluorescence-detection (HERFD) mode, at the U 3d(3/2) (M-4) edge. Thanks to a significant reduction of the core-hole lifetime broadening and distinct chemical shifts of the HERFD-XAS lines, the U(v) formation as a result of La doping was identified. The isolated contribution of U(v) in the M-4 HERFD-XAS spectrum reveals the so-called charge-transfer satellites due to the U 5f-O 2p hybridization. The analysis of the experimental data within the framework of the Anderson impurity model (AIM) indicates a significant change in the characteristics and degree of covalency for the chemical bonding in the U(v) subsystem of UO2 as compared to undoped UO2, which is a Mott-Hubbard system. The results are also supported by AIM calculations of X-ray photoelectron and optical absorption data.

National Category
Chemical Sciences
Identifiers
urn:nbn:se:uu:diva-315832 (URN)10.1039/c6cc07684j (DOI)000391607100012 ()
Available from: 2017-02-21 Created: 2017-02-21 Last updated: 2017-11-29Bibliographically approved
Conradson, S. D., Andersson, D. A., Boland, K. S., Bradley, J. A., Byler, D. D., Durakiewicz, T., . . . Tayal, A. (2017). Closure of the Mott gap and formation of a superthermal metal in the Frohlich-type nonequilibrium polaron Bose-Einstein condensate in UO2+x. Physical Review B, 96(12), Article ID 125114.
Open this publication in new window or tab >>Closure of the Mott gap and formation of a superthermal metal in the Frohlich-type nonequilibrium polaron Bose-Einstein condensate in UO2+x
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2017 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 96, no 12, article id 125114Article in journal (Refereed) Published
Abstract [en]

Mixed valence O-doped UO2+x. and photoexcited UO2 containing transitory U3+ and U5+ host a coherent polaronic quantum phase (CPQP) that exhibits the characteristics of a Frohlich-type, nonequilibrium, phononcoupled Bose-Einstein condensate whose stability and coherence are amplified by collective, anharmonic motions of atoms and charges. Complementary to the available, detailed, real space information from scattering and EXAFS, an outstanding question is the electronic structure. Mapping the Mott gap in UO2, U4O9, and U3O7 with O XAS and NIXS and UM5 RIXS shows that O doping raises the peak of the U5f states of the valence band by similar to 0.4 eV relative to a calculated value of 0.25 eV. However, it lowers the edge of the conduction band by 1.5 eV vs the calculated 0.6 eV, a difference much larger than the experimental error. This 1.9 eV reduction in the gap width constitutes most of the 2-2.2 eV gap measured by optical absorption. In addition, the XAS spectra show a tail that will intersect the occupied U5f states and give a continuous density-of-states that increases rapidly above its constricted intersection. Femtosecond-resolved photoemission measurements of UO2, coincident with the excitation pulse with 4.7 eV excitation, show the unoccupied U5f states of UO2 and no hot electrons. 3.1 eV excitation, however, complements the O-doping results by giving a continuous population of electrons for several eV above the Fermi level. The CPQP in photoexcited UO2 therefore fulfills the criteria for a nonequilibrium condensate. The electron distributions resulting from both excitations persist for 5-10 ps, indicating that they are the final state that therefore forms without passing through the initial continuous distribution of nonthermal electrons observed for other materials. Three exceptional findings are: (1) the direct formation of both of these long lived (> 3-10 ps) excited states without the short lived nonthermal intermediate; (2) the superthermal metallic state is as or more stable than typical photoinduced metallic phases; and (3) the absence of hot electrons accompanying the insulating UO2 excited state. This heterogeneous, nonequilibrium, Frohlich BEC stabilized by a Fano-Feshbach resonance therefore continues to exhibit unique properties.

National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-335203 (URN)10.1103/PhysRevB.96.125114 (DOI)000410002000004 ()
Available from: 2017-12-06 Created: 2017-12-06 Last updated: 2017-12-06Bibliographically approved
Safdari, M., Phuyal, D., Philippe, B., Svensson, P. H., Butorin, S., Kvashnina, K. O., . . . Gardner, J. M. (2017). Impact of synthetic routes on the structural and physical properties of butyl-1,4-diammonium lead iodide semiconductors. Journal of Materials Chemistry A, 5(23), 11730-11738
Open this publication in new window or tab >>Impact of synthetic routes on the structural and physical properties of butyl-1,4-diammonium lead iodide semiconductors
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2017 (English)In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 5, no 23, p. 11730-11738Article in journal (Refereed) Published
Abstract [en]

We report the significant role of synthetic routes and the importance of solvents in the synthesis of organic-inorganic lead iodide materials. Through one route, the intercalation of dimethylformamide in the crystal structure was observed leading to a one-dimensional (1D) [NH3(CH2)(4)NH3]Pb2I6 structure of the product. This product was compared with the two-dimensional (2D) [NH3(CH2)(4)NH3]PbI4 recovered from aqueous solvent based synthesis with the same precursors. UV-visible absorption spectroscopy showed a red-shift of 0.1 eV for the band gap of the 1D network in relation to the 2D system. This shift primarily originates from a shift in the valence band edge as determined from photoelectron-and X-ray spectroscopy results. These findings also suggest the iodide 5p orbital as the principal component in the density of states in the valence band edge. Single crystal data show a change in the local coordination around iodide, while in both materials, lead atoms are surrounded by iodide atoms in octahedral units. The conductivity of the one-dimensional material ([NH3(CH2)(4)NH3]Pb2I6) was 50% of the two-d(i)mensional material ([NH3(CH2)(4)NH3]PbI4). The fabricated solar cells reflect these changes in the chemical and electronic structure of both materials, although the total light conversion efficiencies of solar cells based on both products were similar.

Place, publisher, year, edition, pages
ROYAL SOC CHEMISTRY, 2017
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-329653 (URN)10.1039/c6ta10123b (DOI)000403228200030 ()
Funder
StandUpSwedish Energy AgencySwedish Research CouncilKnut and Alice Wallenberg Foundation
Available from: 2017-09-20 Created: 2017-09-20 Last updated: 2017-09-20Bibliographically approved
Butorin, S. M., Modin, A., Vegelius, J. R., Suzuki, M.-T., Oppeneer, P. M., Andersson, D. A. & Shuh, D. K. (2016). Local Symmetry Effects in Actinide 4f X-ray Absorption in Oxides. Analytical Chemistry, 88(8), 4169-4173
Open this publication in new window or tab >>Local Symmetry Effects in Actinide 4f X-ray Absorption in Oxides
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2016 (English)In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 88, no 8, p. 4169-4173Article in journal (Refereed) Published
Abstract [en]

A systematic X-ray absorption study at actinide N-6,(7) (4f -> 6d transitions) edges was performed for light-actinide oxides including data obtained for the first time for NpO2, PuO2 and UO3. The measurements were supported by ab initio calculations based on local-density approximation. with added 5f-5f Coulomb interaction (LDA+U). Improved energy resolution compared to common experiments at actinide L-2,L-3 (2p -> 6d transitions) edges allowed us to resolve the major structures of the 13 unoccupied 6d density of states (DOS) and estimate the crystal-field 116) splittings in the 6d shell directly from the spectra of light-actinide dioxides. The measurements demonstrated an enhanced sensitivity of the N-6,N-7, spectral shape to changes in the compound crystal structure. For nonstoichiometric NpO2-x, the filling of the entire band gap with Np 6d states was observed thus supporting a phase coexistence of Np metal and stoichiometric NpO2 which is in agreement with the tentative Np-O phase diagram.

National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-297906 (URN)10.1021/acs.analchem.5b04380 (DOI)000374706000001 ()27008406 (PubMedID)
Funder
Swedish Research CouncilEU, FP7, Seventh Framework Programme, 269903Swedish National Infrastructure for Computing (SNIC)
Available from: 2016-06-29 Created: 2016-06-28 Last updated: 2017-11-28Bibliographically approved
Butorin, S. M. M., Modin, A., Vegelius, J., Kvashnina, K. O. & Shuh, D. K. (2016). Probing Chemical Bonding in Uranium Dioxide by Means of High- Resolution X-ray Absorption Spectroscopy. The Journal of Physical Chemistry C, 120(51), 29397-29404
Open this publication in new window or tab >>Probing Chemical Bonding in Uranium Dioxide by Means of High- Resolution X-ray Absorption Spectroscopy
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2016 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, no 51, p. 29397-29404Article in journal (Refereed) Published
Abstract [en]

A systematic X-ray absorption study at the U 3d, 4d, and 4f edges of UO2 was performed, and the data were analyzed within framework of the Anderson impurity model. By applying the high-energy-resolution fluorescence-detection (HERFD) mode of X-ray absorption spectroscopy (XAS) at the U 3d(3/2) edge and conducting the XAS measurements at the shallower U 4f levels, fine details of the XAS spectra were resolved resulting from reduced core-hole lifetime broadening. This multiedge study enabled a far more effective analysis of the electronic structure at the U sites and characterization of the chemical bonding and degree of the 5f localization in UO2. The results support the covalent character of UO2 and do not agree with the suggestions of rather ionic bonding in this compound as expressed in some publications.

National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:uu:diva-315073 (URN)10.1021/acs.jpcc.6b09335 (DOI)000391160400052 ()
Available from: 2017-02-10 Created: 2017-02-10 Last updated: 2017-11-29Bibliographically approved
Modin, A., Suzuki, M.-T., Vegelius, J., Yun, Y., Shuh, D. K., Werme, L., . . . Butorin, S. M. (2015). 5 f-Shell correlation effects in dioxides of light actinides studied by O 1s x-ray absorption and emission spectroscopies and first-principles calculations. Journal of Physics: Condensed Matter, 27(31), Article ID 315503.
Open this publication in new window or tab >>5 f-Shell correlation effects in dioxides of light actinides studied by O 1s x-ray absorption and emission spectroscopies and first-principles calculations
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2015 (English)In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 27, no 31, article id 315503Article in journal (Refereed) Published
Abstract [en]

Soft x-ray emission and absorption spectroscopic data are reported for the O 1s region of a single crystal of UO2, a polycrystalline NpO2 sample, and a single crystal of PuO2. The experimental data are interpreted using first-principles correlated-electron calculations within the framework of the density functional theory with added Coulomb U interaction (DFT+U). A detailed analysis regarding the origin of different structures in the x-ray emission and x-ray absorption spectra is given and the effect of varying the intra-atomic Coulomb interaction-U for the 5f electrons is investigated. Our data indicate that O 1s x-ray absorption and emission spectroscopies can, in combination with DFT+U calculations, successfully be used to study 5f-shell Coulomb correlation effects in dioxides of light actinides. The values for the Coulomb U parameter in these dioxides are derived to be in the range of 4-5 eV.

Keywords
actinide dioxides, x-ray spectroscopy, DFT plus U
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-260803 (URN)10.1088/0953-8984/27/31/315503 (DOI)000358595500007 ()26202182 (PubMedID)
Funder
Swedish Research Council
Available from: 2015-08-31 Created: 2015-08-25 Last updated: 2017-12-04Bibliographically approved
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