1. Chemical (in)stability of an interface between metals and Bi[sub]2Se[sub]3 topological insulatorKatja Ferfolja, Mattia Fanetti, Sandra Gardonio, Matjaž Valant, 2019, published scientific conference contribution abstract Abstract: Our research is dedicated to a study of an interface between a Bi2Se3 topological insulator (TI) and various metals due to the essential need for providing a metal contact for devices. The main objective is to characterize structural and chemical properties at the interface, where the electronic properties of the TI can be affected. The structure of the interface and processes happening at it are investigated by microscopy (SEM, TEM, STM) and spectroscopy techniques (EDX, XPS).
The research started with the noble metals: Ag, Au and Pt. A good stability was observed for Au and Pt, whereas Ag reacted with Bi2Se3 already at room temperature, producing Ag2Se and AgBiSe2 phase. Interface stability was also checked at high temperature and results showed that the Au coating undergoes a coalescence process starting from 100 °C whereas the interface with Pt does not show any change at least up to 350 °C.
At present we are focused on the interface with Ti, a metal which is regularly used as an adhesive layer in electrical contacts. At low coverage (<30 nm) Ti forms an extremely flat film, smoother than Au, Ag or Pt. At higher coverage the film undergoes buckle delamination, likely induced by stress release. The observed morphology indicates that a chemical interaction leads to the growth of the initial smooth Ti epitaxial film. Se interdiffusion and formation of interfacial TixSey phase is envisaged, as suggested from preliminary TEM observations of the interface structure.
The presented results show the importance of the processes happening at the interface, especially solid-state chemical reactions, which are often neglected in the study of systems with metal/TI interfaces. Such instability has to be taken into account since the produced phases can affect transport properties of the material, increase a contact resistance or affect functionality of devices.
Keywords: Bi2Se3, interface, topological insulator, chemical instability
Published in RUNG: 20.08.2021; Views: 1381; Downloads: 9
 Link to full text
This document has many files! More... |
2. Room-temperature solid-state reaction at the Ag/Bi[sub]2Se[sub]3 interfaceKatja Ferfolja, Mattia Fanetti, Iuliia Mikulska, Sandra Gardonio, Matjaž Valant, 2017, published scientific conference contribution abstract Abstract: Topological insulators (TI) are materials that, while having a forbidden bandgap in bulk, are conductors at their surface due to presence of surface-localized electronic states crossing the band gap. [1] TIs are possible because of a time reversal symmetry and spin-orbit coupling, which invert bulk band states in their energy positions and make the bulk band structure non trivial. Consequently, the topological surface states (TSS) emerge on the surface of these materials. Unlike ordinary surface states, TSS cannot be destroyed by contamination or defects on the surface. Additionally, TSS are also spin polarized, which means that when applying current to TI, the current will have a well defined direction of the electron spins.
The topological insulators - a relatively new class of materials - are being widely studied not only from fundamental aspects, but also from their applicative perspectives. It has been predicted that TIs could be used in fields of spintronics, electronics and catalysis. [2,3] Interestingly, only a few studies about metal/TI interfaces have been reported. This is surprising since integration of TI in the applications will often necessitate an interface with the metal, therefore, detailed knowledge on chemistry and electrical conditions at the interface will be required.
In this contribution results on research on the chemistry of the Ag/Bi2Se interface will be presented, in particularonthesolid-statereactionbetweennanoparticles.IthasbeenobservedthatwhenBi2Se3 andAgare put in contact a chemical reaction occurs at the interface, producing AgBiSe2 and Ag2Se. Interestingly, the reaction already occurs at room temperature, which is not usual for solid-state reactions. In literature this reaction has not been properly described. The authors rather described it as intercalation of the silver atoms, which we have disproved and showed that recrystallization of the new phases occurs. [3,4,5] The results will alsobediscussedincomparisonwithothertwoAg/Bi2Se3 systemsunderourinvestigation:i)Agdepositedby achemicalrouteonBi2Se3 nanoflakesandii)AgdepositedfromavapourphaseinvacuumonaBi2Se3.single crystal
Keywords: topological insulators, topological surface states, solid-state reaction, TI/metal interface
Published in RUNG: 20.08.2021; Views: 1462; Downloads: 0
This document has many files! More... |
3. |
4. End-to-end data acquisition pipeline for the Cherenkov Telescope ArrayE. Lyard, Christopher Eckner, Gašper Kukec Mezek, Samo Stanič, Serguei Vorobiov, Lili Yang, Gabrijela Zaharijas, Danilo Zavrtanik, Marko Zavrtanik, 2017, published scientific conference contribution Keywords: CTA, data acquisition, Python interface
Published in RUNG: 16.02.2018; Views: 2637; Downloads: 146
 Full text (326,04 KB) |
5. The emergence of post-cyclic prosody in loanword integration - Toneless Latinate adjectives in Serbo-CroatianMarko Simonović, 2012, published scientific conference contribution Abstract: A case of exceptional assignment of prosody to loanwords is considered. In SerboCroatian,
where in loanwords the original position of stress is generally preserved in some
way, a small class of Latinate adjectives (e.g., element ‚ arna ¯ ‘elementary’ and person ‚ alna ¯ ‘personal’)
become toneless and they display the postcyclic initial falling accent. An account of
these data is proposed which combines a new approach to postcyclic prosody, which is shown
to go hand in hand with syntactically opaque structures, and a new model of loanword integration,
which views the loanword trajectory as lexicalisation. As a result, an enriched theory of
both domains and their interaction arises to account for the data and shed some additional
light on the position of loanwords in the architecture of the grammar/lexicon.
Keywords: loanword integration, postcyclic prosody, prosody/syntax interface, morphology, lexicon
Published in RUNG: 07.02.2018; Views: 3852; Downloads: 0
This document has many files! More... |
6. The role of syntax in stress assignment in Serbo-CroatianBoban Arsenijević, Marko Simonović, 2013, independent scientific component part or a chapter in a monograph Abstract: This chapter analyses a set of interface phenomena showing important correlations between certain phonological regularities on the one hand, and a set of syntactic and semantic properties of the respective expressions on the other. Serbo-Croatian deadjectival nominalizations typically exhibit one of two different prosodic patterns: (1) prosody faithful to the base i.e., surface prosody of the lexical adjective (e.g., Ispraavnoost ‘correctness’, derived from Ispraavan ‘correct’); and (2) a rising span over a long closed penultimate syllable and the syllable following it (e.g., isprAAvnOOst ‘correctness’). The chapter formulates a generalization where, all things being equal, nominalized predicational structures correspond to (1), while nominalized stems correspond to (2). It provides a formal model of the syntactic and semantic as well as the phonological reality of these nominalizations, and an attempt at explaining these facts.
Keywords: deadjectival nominalizations, lexical conservatism, syntax-phonology interface, compositionality, Serbo-Croatian
Published in RUNG: 07.02.2018; Views: 3195; Downloads: 0
This document has many files! More... |
