1. Chemical interactions at the interface of Au on ▫$Bi_2 Se_3$▫ topological insulatorMatjaž Valant, Sandra Gardonio, Saul Estandia, Mattia Fanetti, Andrey Vladimirovich Matetskiy, Polina M. Sheverdyaeva, Paolo Moras, Vasiliki Tileli, 2024, original scientific article Published in RUNG: 01.10.2024; Views: 449; Downloads: 4
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2. Single crystal synthesis and surface electronic structure of Bi_{1.993}Cr_{0.007}Se_{3}Sandra Gardonio, Zipporah Rini Benher, Mattia Fanetti, Paolo Moras, Polina M. Sheverdyaeva, Matjaž Valant, 2024, original scientific article Keywords: topological insulators, magnetic atoms, crystal synthesis, formation of clusters, surface electronic structure
Published in RUNG: 21.08.2024; Views: 779; Downloads: 8
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3. Electronic properties of phases in the quasi-binary Bi[sub]2Se[sub]3-Bi[sub]2S[sub]3 systemZipporah Rini Benher, Sandra Gardonio, Mattia Fanetti, Paolo Moras, Asish K. Kundu, Chiara Bigi, Matjaž Valant, 2021, original scientific article Abstract: We explored the properties of the quasi-binary Bi2Se3–Bi2S3 system over a wide compositional range. X-ray diffraction analysis demonstrates that rhombohedral crystals can be synthesized within the solid solution interval 0–22 mol% Bi2S3, while at 33 mol% Bi2S3 only orthorhombic crystals are obtained. Core level photoemission spectroscopy reveals the presence of Bi3+, Se2− and S2− species and the absence of metallic species, thus indicating that S incorporation into Bi2Se3 proceeds prevalently through the substitution of Se with S. Spin- and angle-resolved photoemission spectroscopy shows that topological surface states develop on the surfaces of the Bi2Se3−ySy (y ≤0.66) rhombohedral crystals, in close analogy with the prototypical case of Bi2Se3, while the orthorhombic crystals with higher S content turn out to be trivial semiconductors. Our results connect unambiguously the phase diagram and electronic properties of the Bi2Se3–Bi2S3 system.
Keywords: topological insulator, quasi-binary Bi2Se3-Bi2S3 system, electronic properties
Published in RUNG: 29.03.2021; Views: 3127; Downloads: 0
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4. Looking for a topological insulator in the tetradymite familyZipporah Rini Benher, Sandra Gardonio, Mattia Fanetti, Polina M. Sheverdyaeva, Paolo Moras, Matjaž Valant, 2019, published scientific conference contribution abstract Abstract: Materials that are topological insulators (TI) manifest a novel state for their electrons. They possess topological surface states that are not destroyed by the presence of non-magnetic impurities on their surfaces. This unique property lies in the bulk band structure and it is typically found in narrow gap semiconductor with strong spin-orbit coupling.
Bi2Se3 and Bi2Te3 belong to the class of compounds called tetradymites and are considered as the 3D-prototypical TI materials. However, these compounds are not usually insulators but have metallic bulk conductivity as a consequence of intrinsic defect doping: vacancies and anti-site defects. For these reasons, it is difficult to electrically gate these materials for the manipulation and control of charge carriers for realizing devices. This led to the search for other topological materials, which might have better insulating behavior in their bulk.
Theoretical studies have pointed out that ternary variants of the Bi2Se3 and Bi2Te3, such as Bi2Te2Se, Bi2Te2S, Bi2Se2S Sb2Te2Se and Sb2Te2S, should be stable TIs and potentially offer a chemical way to control TI behavior, in particular by lowering native doping. Among the cited ternary compounds, Bi2Se2S should manifest a genuine topological spin-transport regime hosting an isolated Dirac cone with the Dirac point in the gap as well. However, it has been poorly studied from the TI experimental perspective.
Therefore, to uncover the full potential of the predicted topological electronic properties of the Bi-Se-S system, in this presentation we will revisit the crystallographic and electronic structure of Bi2Se3-Bi2S3 solid solutions. The combined use of bulk and surface sensitive techniques such as X-ray diffraction (XRD), low energy electron diffraction (LEED), scanning electron microscopy (SEM) with Energy Dispersive X-ray spectroscopy (EDX) and X-ray photoemission spectroscopy (XPS) was applied to analyze single crystal samples grown by us. The quality of the single crystals was suitable for rigorous measurement of the electronic properties by means of Angle Resolved Photoemission Spectroscopy. We unambiguously showed that within a certain solid solution range, the single crystals of Bi-Se-S have a rombohedral structure with the topological surface states as theoretically predicted.
Keywords: topological insulators, ternary tetradymite, electronic properties.
Published in RUNG: 19.12.2019; Views: 4923; Downloads: 0
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5. STUDY OF ELECTRONIC STATES OF THIN METAL FILMS ON HEAVY METAL SURFACES : MASTER'S THESISLuka Novinec, 2018, master's thesis Abstract: V magistrskem delu smo se osredoto£ili na pripravo in karakterizacijo
heterogenih ve£plastnih tankih filmov sestavljenih iz kovin ter teºkih kovin.
Za izdelavo vzorcev smo izbrali dve feromagnetni kovini, Fe in Gd, ter
eno divalentno kovino iz redkih zemelj, Yb. Tanke filme smo nana²ali na
kristalno povr²ino volframa W(110) ter molibdena Mo(110). V primeru Fe
na povr²ini W(110) in Mo(110) ter Yb na pov²ini Mo(110) smo uspe²no
dolo£ili pogoje, potrebne za nana²anje atomsko enakomernih filmov. S pomo
£jo kotno odvisne fotoemisije smo preu£evali kvantna stanja v Fe in Yb
filmih na Mo in W kristalih. Celotno eksperimentalno delo je potekalo na
ºarkovnih linijah VUV-Photoemission in²tituta (ISM-CNR) ter BaDElPh
pri sinhrotronu Elettra v Trstu.
Keywords: electronic states, thin metal films, heavy metal surfaces
Published in RUNG: 04.12.2019; Views: 5154; Downloads: 118
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6. Growth, morphology and stability of Au in contact with the Bi[sub]2Se[sub]3(0 0 0 1) surfaceMattia Fanetti, Iuliia Mikulska, Katja Ferfolja, Paolo Moras, Polina M. Sheverdyaeva, M. Panighel, A. Lodi-Rizzini, I. Píš, S. Nappini, Matjaž Valant, Sandra Gardonio, 2018, original scientific article Keywords: metal contact, topological insulator contact, growth mode, electronic properties, chemical properties, photoemission spectroscopy, microscopy
Published in RUNG: 05.12.2018; Views: 4620; Downloads: 0
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