Academic interests
Physicist/materials scientist with expertise in applying advanced transmission electron microscopy methods on a wide range of energy-related materials. Currently,
- leader of the OScAR 'Operando Screening of emerging Anodes for Na-based stationary storage of Renewable energy' project and
- work package leader of the GoFIB 'Gallium Oxide Fabrication with Ion Beams' project, funded by the Research Council of Norway.
Courses taught
Background
- Research Scientist, Center for Materials Science and Nanotechnology Physics, University of Oslo (2020 - Pres.)
- Postdoctoral fellow, Center for Materials Science and Nanotechnology Physics, University of Oslo (2017-2020)
- PhD in Physics, Department of Physics, Aristotle University of Thessaloniki (2017)
- MSc with distinction in “Materials Physics and Technology” , Department of Physics, Aristotle University of Thessaloniki (2013)
Awards
- 'Young Research Talent' granted by the Research Council of Norway for the OScAR project (2023)
- Highlight talk at EUROMAT Conference/Stockholm/Sweden (2019)
- Best Researcher Grant awarded by the Nordic Microscopy Society/SCANDEM/ Gothenburg/Sweden (2019)
- Best New Researcher Scholarship from IFSM school/18th International Microscopy Congress/Prague/Czech Republic (2014)
- Scholarship awarded by the European Microscopy Society/18th International Microscopy Congress/Prague/Czech Republic (2014)
- Best Poster Award/EMRS Fall Meeting/Warsaw/Poland (2013)
Tags:
SMN,
Structure Physics,
LENS
Publications
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Ravuri, SyamSai; Wrobel, Pawel S.; Gorantla, Sandeep; Bazioti, Kalliopi; Sunding, Martin Fleissner & Lis, Krzysztof
[Show all 11 contributors for this article]
(2024).
High yield and wide lateral size growth of α-Mo2C: exploring the boundaries of CVD growth of bare MXene analogues.
Nanotechnology.
ISSN 0957-4484.
35(15).
doi:
10.1088/1361-6528/ad1c97.
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Synthesis of Mo2C bare MXenes, without surface terminations groups, via chemical vapor deposition (CVD) on metal foils is scientifically a very intriguing crystal growth process, and there are still challenges and limited fundamental understanding to overcome to obtain high yield and wide crystal size lateral growth. Achieving large area coverage via direct growth is scientifically vital to utilize the full potential of their unique properties in different applications. In this study, we sought to expand the boundaries of the current CVD growth approach for Mo2C MXenes and gain insights into the possibilities and limitations of large area growth, with a particular focus on controlling Mo concentration. We report a facile modification of their typical CVD growth protocol and show its influence on the Mo2C synthesis, with growth times spanning up to 3 h. Specifically, prior to initiating the CVD growth process, we introduced a holding step in temperature at 1095 °C. This proved to be beneficial in increasing the Mo concentration on the liquid Cu growth surface. We achieved an average Mo2C crystals coverage of approximately 50% of the growth substrate area, increased tendency of coalescence and merging of individual flakes, and lateral flake sizes up to 170 μm wide. To gain deeper understanding into their CVD growth behavior, we conducted a systematic investigation of the effect of several factors, including (i) a holding step time on Mo diffusion rate through molten Cu, (ii) the Cu foil thickness over the Mo foil, and (iii) the CVD growth time. Phase, chemical and microstructural characterization by x-ray diffraction, x-ray photon spectroscopy, SEM and scanning/transmission electron microscopy revealed that the grown crystals are single phase α-Mo2C. Furthermore, insights gained from this study sheds light on crucial factors and inherent limitations that are essential to consider and may help guide future research progress in CVD growth of bare MXenes.
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Bazioti, Kalliopi; Løvvik, Ole Martin; Poulia, Anthoula; Carvalho, Patricia Almeida; Azar, Amin S. & Mikheenko, Pavlo
[Show all 8 contributors for this article]
(2022).
Probing the structural evolution and its impact on magnetic properties of FeCoNi(AlMn)x high-entropy alloy at the nanoscale.
Journal of Alloys and Compounds.
ISSN 0925-8388.
910,
p. 1–12.
doi:
10.1016/j.jallcom.2022.164724.
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We report the first nanoscale investigation of FeCoNi(AlMn)x high-entropy alloys (HEAs) processed by laser metal deposition. The structural evolution of the alloy upon chemical composition variation (0.2 ≤ x ≤ 1.5) was investigated by combining imaging and spectroscopies in (scanning) transmission electron microscopy (S)TEM with density functional theory (DFT). A gradual change from a face-centered cubic (FCC) towards an ordered full-Heusler (L21) phase by increasing the Al and Mn contents was observed. Direct imaging and atomic-scale calculations revealed a nanoscale interplay between B2 and L21 ordered structures for x = 1.5, wherein the latter, Al and Mn occupy two different Wyckoff sites. By decreasing x, the FCC phase dominates exhibiting intense phase separation tendency, ordering phenomena, and nano-precipitation. Although not chemically discriminated, plasmon-peak splitting in low-loss electron energy loss spectra revealed the presence of two valence electron densities within the FCC phase. Lorentz TEM showed that the ordered nano-precipitates and nano-sized grains with a structure based on a tripled FCC unit cell are pinning-sites for magnetic domain walls and dislocations. All alloy compositions exhibited soft-magnetic behavior with coercivity (Hc) values< 1000 A/m. The FeCoNi(AlMn)1.5 alloy with L21/B2 nanostructure showed the highest magnetization (Ms) with relatively low Hc, attributed to the large magnetic moment of Mn and the synergistic effect of Mn-Al according to DFT, whilst ordering does not impose a negative effect. Phase separation trends within the FCC phase seem to decrease the Ms however, the overall impact on the magnetic behavior is not intense, opening up for new avenues for tuning FeCoNiAlMn properties through chemically-designed phase decomposition regimes.
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Schifano, Ramon; Wierzbicka, A.; Dluzewski, P.; Domagala, J.Z.; Wozniak, W. & Kurowska, B.
[Show all 8 contributors for this article]
(2022).
The restricted random dislocation distribution model to describe ensembles of dislocations with a screw component in ZnO layers with a mosaic structure.
Journal of Applied Physics.
ISSN 0021-8979.
132(5),
p. 1–11.
doi:
10.1063/5.0086295.
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By applying the restricted random dislocation distribution model, solved using a discrete Hankel transform approach, it is shown that the
shapes and characteristics of the ω-scans of the ZnO 00.2 reflection are mainly determined by the strain field introduced by dislocations
with a screw component. On the other hand, no clear evidence of mosaicity or interfacial region contributions is found despite the layers
exhibiting a c axis oriented residual columnar structure and a highly defective interface being present. The applied model not only permits a
more precise estimation of the densities of dislocations, which present a screw component with respect to methods based on the analysis of
the 00.2 peak ω-scan FWHM, but also gives an indication of their distribution characteristics with the extracted values, as well as their
homogeneous/quasi-regular spacing, being confirmed by cross-sectional transmission electron microscopy observations.
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Azarov, Alexander; Bazioti, Kalliopi; Venkatachalapathy, Vishnukanthan; Ponniah, Vajeeston; Monakhov, Eduard & Kuznetsov, Andrej
(2022).
Disorder-Induced Ordering in Gallium Oxide Polymorphs.
Physical Review Letters.
ISSN 0031-9007.
128(1).
doi:
10.1103/PhysRevLett.128.015704.
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olymorphs are common in nature and can be stabilized by applying external pressure in materials. The pressure and strain can also be induced by the gradually accumulated radiation disorder. However, in semiconductors, the radiation disorder accumulation typically results in the amorphization instead of engaging polymorphism. By studying these phenomena in gallium oxide we found that the amorphization may be prominently suppressed by the monoclinic to orthorhombic phase transition. Utilizing this discovery, a highly oriented single-phase orthorhombic film on the top of the monoclinic gallium oxide substrate was fabricated. Exploring this system, a novel mode of the lateral polymorphic regrowth, not previously observed in solids, was detected. In combination, these data envisage a new direction of research on polymorphs in Ga2O3 and, potentially, for similar polymorphic families in other materials.
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Soltani, Nayereh; Rahman, Jamil Ur; Carvalho, Patricia Almeida; Bazioti, Kalliopi & Finstad, Terje Gunnar
(2022).
From quaternary to senary high entropy antimonide nanoparticles by a facile and scalable thermal treatment method.
Materials research bulletin.
ISSN 0025-5408.
153.
doi:
10.1016/j.materresbull.2022.111873.
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Transition metal antimonides form a class of intermetallic compounds, which has drawn considerable attention due to their potential applications in various fields. However, the formation of nanostructures containing multiple transition metal elements has been a challenge. Here, a new class of multicomponent antimonide nanoparticles with chemical composition ranging from quaternary to senary were synthesized via a simple, reproducible, and scalable thermal treatment method. This method allows uniform elemental distributions in a single nanoparticle, demonstrating the ability to obtain medium- and high-entropy antimonide nanostructures. The mechanism of formation was proposed and the characteristics of obtained nanoparticles were investigated by X-ray diffraction, field emission scanning electron microscopy, and high-resolution transmission electron microscopy. Under the achieved optimal synthesis conditions, the formation of a single-phase with a hexagonal structure (P63/mmc) was observed for the quaternary and quinary samples, whereas in the case of the senary samples, a trace of minor impurity can be observed.
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Larsen, Aleksander Amble; Poulia, Anthoula; Azar, Amin S.; Bazioti, Kalliopi; Carvalho, Patricia Almeida & Gunnæs, Anette Eleonora
[Show all 9 contributors for this article]
(2021).
Identifying Magnetic Phases in Additively Manufactured High-Entropy Alloy FeCoNiAlxMnx,
2021 IEEE 10th International Conference on “Nanomaterials: Applications & Properties” (NAP – 2021).
IEEE (Institute of Electrical and Electronics Engineers).
ISSN 9781665439077.
p. NMM03-1–NMM03-4.
doi:
10.1109/NAP51885.2021.9568591.
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High-Entropy Alloys are advanced technological materials composed of several (typically five) elements in nearly equal atomic concentration. By forming these alloys, previously unknown phase fields of multidimensional phase diagrams are explored. The large number of possible substitutions of constituent elements on crystal lattice sites justifies the dominant contribution of mixing entropy over enthalpy to the free energy reduction. This leads to the formation of phases, which otherwise could not be formed in alloys with fewer main alloying elements. Here we explore magnetic and compositional properties of a High-Entropy Alloy, namely FeCoNiAl x Mn x (0.05 ≤ x ≤ 3.08), composed of magnetic (Fe, Co, Ni) and non-magnetic elements (Al, Mn). By magnetic force microscopy of a selected area, it is observed that for intermediate to low Al and Mn contents, the alloy splits in two major crystallographic phases with different magnetic properties. Elemental maps of the same area were recorded with energy dispersive spectroscopy and scanning electron microscopy. Counterintuitively, it was found that the phase rich in non-magnetic Al has stronger magnetism than the phase rich in Fe. This work showcases possible applications of the here presented HEAs as soft magnetic materials in functional magnetic elements.
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Poulia, Anthoula; Azar, Amin S.; Schrade, M.; Graff, J.S.; Bazioti, Kalliopi & Gunnæs, Anette Eleonora
[Show all 8 contributors for this article]
(2021).
Process–Structure–Property Relationship in FeCoNiAlxMnx Complex Concentrated Alloys Processed by Additive Manufacturing.
Journal of materials engineering and performance (Print).
ISSN 1059-9495.
30(9),
p. 6961–6971.
doi:
10.1007/s11665-021-06082-8.
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Fourteen alloys of the FeCoNiAlxMnx system were processed by laser metal deposition (LMD). The feedstock was a weighted and proportional blend of the containing elemental powders, targeting the nominal alloy compositions. Prior to processing, the composition and particle characteristics of the feedstock were assessed. The microstructural features and crystal structures of all LMD processed materials were characterized with scanning electron microscopy/energy dispersive spectroscopy and x-ray diffraction, in both as-received and heat-treated conditions. Selected samples were investigated via scanning transmission electron microscopy and electron backscattered diffraction for further structural understanding. Hardness tests, under various indentation loads and dwelling times, were performed to assess the mechanical properties of the processed samples. The results showed a rise in hardness as Al and Mn contents increase. The variation of hardness with composition follows a reverse sigma-type curve, reflecting the microstructural evolution and grain size variations in the alloys. Based on the hardness data, we suggest a trained and validated predictive model, which can be used in alloy design for future developments.
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Kang, Xiaolan; Berberidou, Chrysanthi; Galeckas, Augustinas; Bazioti, Kalliopi; Sagstuen, Einar & Norby, Truls Eivind
[Show all 8 contributors for this article]
(2021).
Visible Light Driven Photocatalytic Decolorization and Disinfection of Water Employing Reduced TiO2 Nanopowders.
Catalysts.
11(2).
doi:
10.3390/catal11020228.
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Defect-engineering of TiO2 can have a major impact on its photocatalytic properties for the degradation of persisting and non-biodegradable pollutants. Herein, a series of intrinsic and extrinsic defects are induced by post annealing of crystalline TiO2 under different reducing atmospheres. A detailed optoelectronic characterization sheds light on the key characteristics of the defect-engineered TiO2 nanopowders that are linked to the photocatalytic performance of the prepared photocatalysts. The photodegradation of a model dye, malachite green, as well as the inactivation of bacterial endospores of the Geobacillus stearothermophilus species were studied in the presence of the developed catalysts under visible light illumination. Our results indicate that a combination of certain defects is necessary for the improvement of the photocatalytic process for water purification and disinfection under visible light.
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Vasileiadis, Isaak G.; Belabbas, Imad; Bazioti, Kalliopi; Smalc-Koziorοwska, Julita; Komninou, Philomela & Dimitrakopulos, George P.
(2021).
Stacking Fault Manifolds and Structural Configurations of Partial Dislocations in InGaN Epilayers.
Physica status solidi (b).
ISSN 0370-1972.
258,
p. 2100190–2100190.
doi:
10.1002/pssb.202100190.
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Gogova-Petrova, Daniela; Olsen, Vegard Skiftestad; Bazioti, Kalliopi; Lee, In-Hwan; Prytz, Øystein & Vines, Lasse
[Show all 7 contributors for this article]
(2020).
High electron mobility single-crystalline ZnSnN2 on ZnO (0001) substrates.
CrysteEngComm.
22(38),
p. 6268–6274.
doi:
10.1039/d0ce00861c.
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Making a systematic effort, we have developed single-crystalline ZnSnN2 on ZnO (0001) by reactive magnetron co-sputtering. Epitaxial growth was achieved at 350 °C by co-sputtering from metal targets in a nitrogen atmosphere, and confirmed by transmission electron microscopy (TEM) measurements. TEM verified that the layers are single-crystalline of hexagonal phase, exhibiting an epitaxial relationship with the substrate described by: [11−20]ZnSnN2//[11−20]ZnO and [0001]ZnSnN2//[0001]ZnO. The screw-type threading dislocations originating from the ZnSnN2/ZnO interface were identified as the dominant extended defects. More specifically, we report a pioneering measurement of the dislocation density in this material of 1.5 × 1011 cm−2. Even though there are no literature data for direct comparison, such values are typical of heteroepitaxial growth of III-nitride layers without applying defect density reduction strategies. The films demonstrated a high electron mobility of 39 cm2 V−1 s−1 and 63 cm2 V−1 s−1 for stoichiometric and Zn-rich layers, respectively, while the electron carrier density remained in the low 1019 cm−3 range as determined by the Hall effect measurements at room temperature. Optical bandgaps of 1.86 eV and 1.72 eV were determined for the stoichiometric and Zn-rich samples, respectively. As such, we conclude that ZnSnN2 is an earth-abundant, environmentally-friendly semiconductor and is a promising candidate for cost efficient components in optoelectronics and photovoltaics.
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Smalc-Koziorοwska, Julita; Moneta, J.; Chatzopoulou, P.; Vasileiadis, I.G.; Bazioti, Kalliopi & Prytz, Øystein
[Show all 9 contributors for this article]
(2020).
The heterogeneous nucleation of threading dislocations on partial dislocations in III-nitride epilayers.
Scientific Reports.
10.
doi:
10.1038/s41598-020-74030-y.
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Abstract III-nitride compound semiconductors are breakthrough materials regarding device applications. However, their heterostructures suffer from very high threading dislocation (TD) densities that impair several aspects of their performance. The physical mechanisms leading to TD nucleation in these materials are still not fully elucidated. An overlooked but apparently important mechanism is their heterogeneous nucleation on domains of basal stacking faults (BSFs). Based on experimental observations by transmission electron microscopy, we present a concise model of this phenomenon occurring in III-nitride alloy heterostructures. Such domains comprise overlapping intrinsic I 1 BSFs with parallel translation vectors. Overlapping of two BSFs annihilates most of the local elastic strain of their delimiting partial dislocations. What remains combines to yield partial dislocations that are always of screw character. As a result, TD nucleation becomes geometrically necessary, as well as energetically favorable, due to the coexistence of crystallographically equivalent prismatic facets surrounding the BSF domain. The presented model explains all observed BSF domain morphologies, and constitutes a physical mechanism that provides insight regarding dislocation nucleation in wurtzite-structured alloy epilayers.
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Poulia, Anthoula; Azar, Amin S.; Svec, Peter; Bazioti, Kalliopi; Belle, Branson & Gunnæs, Anette Eleonora
[Show all 8 contributors for this article]
(2020).
Nanoscale Magnetic Properties of Additively Manufactured FeCoNiAlxMnx High-Entropy Alloys,
2020 IEEE 10th International Conference on
“Nanomaterials: Applications & Properties”
(NAP – 2020).
IEEE (Institute of Electrical and Electronics Engineers).
ISSN 9781728185064.
p. 01NMM02-1–01NMM02-5.
doi:
10.1109/NAP51477.2020.9309571.
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Magnetic properties of High-Entropy Alloys based on the Fe-Co-Ni-Al-Mn system are reported. High-Entropy Alloys are cutting-edge technological materials containing five or more elements in relatively high concentrations (5–35 at.%) within one or several solid-state solutions. These solutions are stabilized at the nanometer scale due to the high contribution of the mixing entropy to the Gibbs free energy, which can overcome the enthalpic contribution. Two magnetic alloys are found in FeCoNiAlxMnx (1.6 at.% x 7.8 at.%) samples processed by laser metal deposition. The magnetic techniques used to screen the materials were magneto-optical imaging and magnetic force microscopy. The former allows characterizing magnetic properties within the mm-μm scale, while the latter is efficient down to the nanometer scale. Magnetic screening confirms the importance of the nanostructure in defining magnetic properties of the alloys, and the trends in the magnetic behavior as a function of the alloy composition are revealed. The experimental results suggest that it is possible to form unique alloys, which may outperform conventional magnetic materials used in a variety of applications such as transformers, screening shields and wind power generators.
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Øien-Ødegaard, Sigurd; Bazioti, Kalliopi; Redekop, Evgeniy; Prytz, Øystein; Lillerud, Karl Petter & Olsbye, Unni
(2020).
A toroidal Zr70 oxysulfate cluster and its diverse packing structures.
Angewandte Chemie International Edition.
ISSN 1433-7851.
59,
p. 21397–21402.
doi:
10.1002/anie.202010847.
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Herein, we report the discovery of a toroidal inorganic cluster of zirconium(IV) oxysulfate of unprecedented size with the formula Zr70(SO4)58(O/OH)146⋅x(H2O) (Zr70), which displays different packing of ring units and thus several polymorphic crystal structures. The ring measures over 3 nm across, has an inner cavity of 1 nm and displays a pseudo‐10‐fold rotational symmetry of Zr6 octahedra bridged by an additional Zr in the outer rim of the ring. Depending on the co‐crystallizing species, the rings form various crystalline phases in which the torus units are connected in extended chain and network structures. One phase, in which the ring units are arranged in layers and form one‐dimensional channels, displays high permanent porosity (BET surface area: 241 m2 g−1), and thus demonstrates a functional property for potential use in, for example, adsorption or heterogeneous catalysis.
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Bazioti, Kalliopi; Olsen, Vegard Skiftestad; Kuznetsov, Andrej; Vines, Lasse & Prytz, Øystein
(2020).
Formation of N2 bubbles along grain boundaries in (ZnO)1−x(GaN)x: nanoscale STEM-EELS studies.
Physical Chemistry, Chemical Physics - PCCP.
ISSN 1463-9076.
22(7),
p. 3779–3783.
doi:
10.1039/c9cp06025a.
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Direct evidence of N2 formation after annealing of (ZnO)1−x(GaN)x alloys was revealed. N2 was trapped by VZn+Ga-clusters, forming faceted voids along grain boundaries. This study shows that N–N bonding is a competitive path for nitrogen after annealing, in addition to the increasing Ga–N bonds, indicating that N in O substitution sites (NO) is not a stable configuration.
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Vasquez, Geraldo Cristian; Bathen, Marianne Etzelmüller; Galeckas, Augustinas; Bazioti, Kalliopi; Johansen, Klaus Magnus H & Maestre, D.
[Show all 11 contributors for this article]
(2020).
Strain Modulation of Si Vacancy Emission from SiC Micro- and Nanoparticles.
Nano Letters.
ISSN 1530-6984.
20(12),
p. 8689–8695.
doi:
10.1021/acs.nanolett.0c03472.
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Single-photon emitting point defects in semiconductors have emerged as strong candidates for future quantum technology devices. In the present work, we exploit crystalline particles to investigate relevant defect localizations, emission shifting, and waveguiding. Specifically, emission from 6H-SiC micro- and nanoparticles ranging from 100 nm to 5 μm in size is collected using cathodoluminescence (CL), and we monitor signals attributed to the Si vacancy (VSi) as a function of its location. Clear shifts in the emission wavelength are found for emitters localized in the particle center and at the edges. By comparing spatial CL maps with strain analysis carried out in transmission electron microscopy, we attribute the emission shifts to compressive strain of 2–3% along the particle a-direction. Thus, embedding VSi qubit defects within SiC nanoparticles offers an interesting and versatile opportunity to tune single-photon emission energies while simultaneously ensuring ease of addressability via a self-assembled SiC nanoparticle matrix.
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Olsen, Vegard Skiftestad; Bazioti, Kalliopi; Baldissera, Gustavo; Azarov, Alexander; Prytz, Øystein & Persson, Clas
[Show all 9 contributors for this article]
(2019).
Effects of Substrate and Post-Deposition Annealing on Structural and Optical Properties of (ZnO)1-x(GaN)x Films.
Physica status solidi (b).
ISSN 0370-1972.
256(6).
doi:
10.1002/pssb.201800529.
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The structural and optical properties of magnetron sputtered thin films of (ZnO)1−x(GaN)x deposited on zinc oxide, sapphire, and silicon oxide are studied as a function of strain accumulation and post‐deposition anneals at 600–800 °C. For the experimental conditions studied, we found that different amounts of tensile strain accumulated in the samples practically does not affect the strong bandbowing effect, that is, optical bandgap, observed in the as‐deposited alloys. In its turn, post‐deposition annealing results in a reduction of the tensile strain and dislocation density in the films, as measured by both X‐ray diffraction and transmission electron microscopy, corroborating an increase in the crystal quality. In addition, the grain size is found to increase with annealing temperature, for example, mean values of 20 nm up to 50 nm were measured for the alloys with x = 0.15. Meanwhile, the full‐width at half maximum of the (0002) X‐ray diffraction reflection increases with annealing temperature, but with only a small increase in bandgap energies for the x = 0.15 sample. However, this observation was explained combining the experimental data and first‐principles calculations based on density functional theory, showing that the increase in the amount of Ga‐N bonds lowers the total energy of the system. As such, we conclude that the thermal treatments increase the Ga‐N ordering, resulting in several contributions or a widening of the diffraction peaks.
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Olsen, Vegard Skiftestad; Baldissera, Gustavo; Zimmermann, Christian; Granerød, Cecilie Skjold; Bazioti, Kalliopi & Galeckas, Augustinas
[Show all 11 contributors for this article]
(2019).
Evidence of defect band mechanism responsible for band gap evolution in (ZnO)1−x(GaN)x alloys.
Physical review B (PRB).
ISSN 2469-9950.
100(16).
doi:
10.1103/PhysRevB.100.165201.
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It is known that (ZnO)1−x(GaN)x alloys demonstrate remarkable energy band bowing, making the material absorb in the visible range, in spite of the binary components being classical wide band gap semiconductors. However, the origin of this bowing is not settled; two major mechanisms are under debate: Influence of the orbital repulsion and/or formation of a defect band. In the present work, we applied a combination of the absorption and emission measurements on the samples exhibiting an outstanding nanoscale level of (ZnO)1−x(GaN)x homogeneity as monitored by the high resolution electron microscopy equipped with the energy dispersive x-ray analysis and the electron energy loss spectroscopy; moreover the experimental data were set in the context of the computational analysis of the alloys employing density functional theory and quasiparticle GW approximation. A prominent discrepancy in the band gap values as deduced from the absorption and emission experiments was observed systematically for the alloys with different compositions and interpreted as evidence for the absorption gap shrinking due to the defect band formation. Computational data support the argument, revealing only minor variations in the bulk of the conduction and valence band structures of the alloys, except for a characteristic “tail” in the vicinity of the valence band maximum. As such, we conclude that the energy gap bowing in (ZnO)1−x(GaN)x alloys is due to the defect band formation, presumably at the top of the valence band maximum.
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Hjelmeland, Trude Bjørgås; Bazioti, Kalliopi; Gunnæs, Anette Eleonora; Volkov, Y & Mikheenko, Pavlo
(2019).
Effect of colossal magnetoresistance material La0.67Ca0.33MnO3 on superconducting properties of YBa2Cu3O7-δ thin films.
Journal of Magnetism and Magnetic Materials.
ISSN 0304-8853.
487.
doi:
10.1016/j.jmmm.2019.165335.
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By specific design of the sample, in which SrTiO3 substrate is fully covered by a thin layer of the colossal magnetoresistive material La0.67Ca0.33MnO3 (LCMO) and the latter is partially covered by high-temperature superconductor YBa2Cu3O7-δ (YBCO), and by using multiple current and voltage contacts, direct evidence of the strong effect of LCMO on YBCO is obtained. It is found that LCMO strongly influences not only superconducting, but also normal state of YBCO, and it is argued that this is a consequence of the spin injection from the former to the latter. The effect of the deposition conditions and crystal orientation of YBCO layer on this effect is clarified. A surprising peak in the temperature dependence of resistance seen in ex-situ ab-plane oriented sample is explained as a combination of two effects: influence of spin-polarized electrons on superconductor below its critical temperature and the interface-controlled shift of Curie temperature of LCMO to low temperatures. Considering expected use of LCMO and YBCO in composite quantum computation circuits, their combination with another advanced quantum material, graphene, is explored.
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Bondevik, Tarjei; Ness, Heine Håland; Bazioti, Kalliopi; Norby, Truls Eivind; Løvvik, Ole Martin & Koch, Christoph T.
[Show all 7 contributors for this article]
(2019).
Investigation of the electrostatic potential of a
grain boundary in Y-substituted BaZrO3 using
inline electron holography.
Physical Chemistry, Chemical Physics - PCCP.
ISSN 1463-9076.
21(32),
p. 17662–17672.
doi:
10.1039/c9cp02676b.
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We apply inline electron holography to investigate the electrostatic potential across an individual BaZr0.9Y0.1O3 grain boundary. With holography, we measure a grain boundary potential of −1.3 V. Electron energy loss spectroscopy analyses indicate that barium vacancies at the grain boundary are the main contributors to the potential well in this sample. Furthermore, geometric phase analysis and density functional theory calculations suggest that reduced atomic density at the grain boundary also contributes to the experimentally measured potential well.
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Bazioti, Kalliopi; Azarov, Alexander; Johansen, Klaus Magnus H; Svensson, Bengt Gunnar; Vines, Lasse & Kuznetsov, Andrej
[Show all 7 contributors for this article]
(2019).
Role of Nitrogen in Defect Evolution in Zinc Oxide: STEM−EELS
Nanoscale Investigations.
The Journal of Physical Chemistry Letters.
10(16),
p. 4725–4730.
doi:
10.1021/acs.jpclett.9b01472.
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Direct evidence of the formation of nitrogen molecules (N2) after ion implantion of ZnO has been revealed by an atomically resolved scanning transmission electron microscopy (STEM)–electron energy-loss spectroscopy (EELS) investigation. Taking advantage of the possibility of using multiple detectors simultaneously in aberration-corrected STEM, we utilize the detailed correlation between the atomic structure and chemical identification to develop a model explaining the formation and evolution of different defect types and their interaction with N. In particular, the formation of zinc vacancy (VZn) clusters filled with N2 after heat treatment at 650 °C was observed, clearly indicating that N has not been stabilized in the O substitution site, thus limiting p-type doping. Previous results showing an exceptional thermal stability of vacancy clusters only for the case of N-doped ZnO are supported. Furthermore, VZn–N2 stabilization leads to suppression of VZn–Zni recombination; hence, the highly mobile Zn interstitials preferentially condense on the basal planes promoting formation of extended defects (basal stacking faults and stacking mismatched boundaries). The terminations of these defects provide energetically favorable sites for further N2 trapping as a way to reduce local strain fields.
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Mishra, Mochan; Berdiell, Izar Capel; Bazioti, Kalliopi & Koposov, Alexey
(2026).
Revealing electrolyte-dependent behavior of Sn-based CA anodes for Na-ion batteries.
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Bazioti, Kalliopi; Azarov, Alexander; Vines, Lasse; Prytz, Øystein & Kuznetsov, Andrej
(2026).
Fundamental insights into polymorphism and defect evolution in ion-irradiated semiconductors by employing atomic-scale Transmission Electron Microscopy.
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Bazioti, Kalliopi
(2025).
The becoming of 'Solid-State Physics and Quantum Technology' group: 10 years of TEM activity.
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Bazioti, Kalliopi
(2024).
In situ growth and operando (S)TEM investigation of 2D anodes for all-solid-state Li-ion batteries.
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Bazioti, Kalliopi; Kneiβ, Max; Wenckstern, Holger Von; Hage, Fredrik Sydow & Prytz, Øystein
(2022).
Band Gap Measurements by VEELS
of novel κ-(Al0.2Ga0.8)2O3/ κ-(In0.25Ga0.75)2O3 superlattices.
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Azarov, Alexander; Bazioti, Kalliopi; Venkatachalapathy, Vishnukanthan; Vajeeston, Ponniah; Monakhov, Eduard & Kuznetsov, Andrej
(2022).
Disorder-induced ordering in Ga2O3 polymorphs.
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Azarov, Alexander; Bazioti, Kalliopi; Venkatachalapathy, Vishnukanthan; Vajeeston, Ponniah; Monakhov, Eduard & Kuznetsov, Andrej
(2022).
Ion-beam-induced phase transitions in gallium oxide: impact of the implantation temperature.
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Bazioti, Kalliopi; Poulia, Anthoula; Løvvik, Ole Martin; Carvalho, Patricia Almeida; Azar, Amin S. & Mikheenko, Pavlo
[Show all 8 contributors for this article]
(2021).
STEM-EELS investigations and Lorentz microscopy unravelling the
structural evolution of FeCoNi(AlMn)x high-entropy alloy
and its impact on magnetic properties.
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Bazioti, Kalliopi
(2021).
Transmission Electron Microscopy studies on resolving Energy Materials properties: Semiconductors, Metal alloys, 2D-based anodes for Batteries.
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Poulia, Anthoula; Azar, Amin S.; Gunnæs, Anette Eleonora; Bazioti, Kalliopi; Mikheenko, Pavlo & Diplas, Spyridon
(2021).
Tailoring mechanical and magnetic properties of the FeCoNi(AlMn)x high entropy alloys via compositional alterations.
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Poulia, Anthoula; Azar, Amin S.; Bazioti, Kalliopi; Gunnæs, Anette Eleonora; Mikheenko, Pavlo & Diplas, Spyridon
(2021).
Additively manufactured FeCoNi(AlMn)x high entropy alloys: Mechanical and magnetic properties investigation.
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Poulia, Anthoula; Azar, Amin S.; Bazioti, Kalliopi; Gunnæs, Anette Eleonora; Mikheenko, Pavlo & Diplas, Spyridon
(2021).
Investigation of High Entropy Alloys via Magnetic Force Microscopy.
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Bazioti, Kalliopi
(2021).
(S)TEM investigations of Energy Materials: Semiconductors, Metal Alloys and 2D-based anodes for Batteries.
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Bazioti, Kalliopi
(2020).
Novel (M,Ga)2O3 thin film heterostructures:
preliminary Transmission Electron Microscopy investigations.
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Poulia, Anthoula; Azar, Amin S.; Svec, Peter; Bazioti, Kalliopi; Belle, Branson & Gunnæs, Anette Eleonora
[Show all 8 contributors for this article]
(2020).
Nanoscale Magnetic Properties of Additively Manufactured FeCoNiAlxMnx High-Entropy Alloys.
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Show summary
Magnetic properties of High-Entropy Alloys based on the Fe-Co-Ni-Al-Mn system are reported. High-Entropy Alloys are cutting-edge technological materials containing five or more elements in relatively high concentrations (5–35 at.%) within one or several solid-state solutions. These solutions are stabilized at the nanometer scale due to the high contribution of the mixing entropy to the Gibbs free energy, which can overcome the enthalpic contribution. Two magnetic alloys are found in FeCoNiAlxMnx (1.6 at.% x 7.8 at.%) samples processed by laser metal deposition. The magnetic techniques used to screen the materials were magneto-optical imaging and magnetic force microscopy. The former allows characterizing magnetic properties within the mm-μm scale, while the latter is efficient down to the nanometer scale. Magnetic screening confirms the importance of the nanostructure in defining magnetic properties of the alloys, and the trends in the magnetic behavior as a function of the alloy composition are revealed. The experimental results suggest that it is possible to form unique alloys, which may outperform conventional magnetic materials used in a variety of applications such as transformers, screening shields and wind power generators.
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Haug, Kristian; Nguyen, Phuong Dan; Karlsen, Ole Bjørn; Aarholt, Thomas; Bazioti, Kalliopi & Prytz, Øystein
(2019).
Zinc ferrite spinel embedded in ZnO matrix for solar applications.
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Bazioti, Kalliopi; Olsen, Vegard Skiftestad; Azarov, Alexander; Kuznetsov, Andrej; Vines, Lasse & Prytz, Øystein
(2019).
Defect formation and thermal evolution in ZnO-based structures (Highlight talk).
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Bazioti, Kalliopi
(2019).
Quantification of chemical inhomogeneities in III-V ternary alloys by Valence Electron Energy-Loss Spectroscopy.
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Bazioti, Kalliopi; Olsen, Vegard Skiftestad; Alexander, Azarov; Kuznetsov, Andrej; Vines, Lasse & Prytz, Øystein
(2019).
STEM-EELS investigation of defect formation and thermal evolution in ZnO.
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Bazioti, Kalliopi; Granerød, Cecilie Skjold; Olsen, Vegard Skiftestad; Vines, Lasse; Svensson, Bengt Gunnar & Prytz, Øystein
(2018).
(ZnO)1-X(GaN)X thin films studied by high-resolution structural and spectroscopic imaging.
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Bazioti, Kalliopi; Azarov, Alexander; Svensson, Bengt Gunnar & Prytz, Øystein
(2018).
An aberration-corrected (S)TEM study of N-induced defects in ZnO: formation and thermal evolution.
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Bazioti, Kalliopi; Granerød, Cecilie Skjold; Olsen, Vegard Skiftestad; Vines, Lasse; Svensson, Bengt Gunnar & Prytz, Øystein
(2018).
Structural-chemical characterization and bandgap measurements at the nanoscale of (ZnO)1-X(GaN)X thin films using (S)TEM methods.
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Bazioti, Kalliopi; Azarov, Alexander; Svensson, Bengt Gunnar & Prytz, Øystein
(2018).
(S)TEM characterization and thermal evolution of ion-induced defects in ZnO.
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Bazioti, Kalliopi; Granerød, Cecilie Skjold; Olsen, Vegard Skiftestad; Vines, Lasse; Svensson, Bengt Gunnar & Prytz, Øystein
(2017).
Structural characterization and nanoscale bandgap measurements of (ZnO)1-X(GaN)X thin films.
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Bazioti, Kalliopi; Granerød, Cecilie Skjold; Olsen, Vegard Skiftestad; Vines, Lasse; Svensson, Bengt Gunnar & Prytz, Øystein
(2017).
Structural/chemical characterization and bandgap measurements of (ZnO)1-X(GaN)X thin films using (S)TEM methods.
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Bazioti, Kalliopi; Granerød, Cecilie Skjold; Olsen, Vegard Skiftestad; Vines, Lasse; Svensson, Bengt Gunnar & Prytz, Øystein
(2017).
(S)TEM characterization of magnetron sputtered ZnO:GaN alloy thin films.
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Bazioti, Kalliopi; Granerød, Cecilie Skjold; Olsen, Vegard Skiftestad; Vines, Lasse; Svensson, Bengt Gunnar & Prytz, Øystein
(2017).
Structural and chemical characterization of (ZnO)1-X(GaN)X thin films using (S)TEM methods.
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Published
Mar. 29, 2017 2:05 PM
- Last modified
Dec. 16, 2024 3:53 PM
