1. Lattice-matched ▫$Ta_3N_5/Nb_5N_6$▫ interface enables a bulk charge separation efficiency of close to 100%Yitong Liu, Zeyu Fan, Ronghua Li, Andraž Mavrič, Iztok Arčon, Matjaž Valant, Gregor Kapun, Beibei Zhang, Chao Feng, Zemin Zhang, 2025, original scientific article Abstract: The interface between the semiconductor light absorber
and the metal electrode is critical for facilitating the extraction of photogenerated charges in photoelectrodes. Achieving a lattice-matched
semiconductor/electrode interface with low defect density is highly desirable but remains a challenge for Ta3N5 photoanodes. In this study, we synthesized niobium nitride thin film electrodes with controllable crystallographic phases to achieve a lattice-matched Ta3N5/Nb5N6 back contact. This results in an enhanced crystallinity of the Ta3N5 film and
reduced interfacial defect density. Consequently, the photoanode with the lattice-matched back contact attains a record half-cell solar-to-hydrogen conversion efficiency of 4.1%, attributed to the bulk carrier separation efficiency of nearly 100%. This work highlights lattice-matching as an effective strategy to enhance the efficiency of thin film-based solar energy conversion devices.
Keywords: photoelectrochemistry, photoanode, interface, semiconductors
Published in RUNG: 28.03.2025; Views: 353; Downloads: 3
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2. The interface between Pt and ▫$Bi_2Se_3$▫ : instability and formation of a new ordered phaseMattia Fanetti, Katja Ferfolja, Sandra Gardonio, Matjaž Valant, 2024, original scientific article Keywords: topological insulator, platinum, interface, thin film, TEM, intermetallic
Published in RUNG: 28.01.2025; Views: 666; Downloads: 5
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4. Understanding the in-situ transformation of ▫$Cu_xO$▫ interlayers to increase the water splitting efficiency in NiO/n-Si photoanodesChao Feng, Zhi Liu, Huanxin Ju, Andraž Mavrič, Matjaž Valant, Jie Fu, Beibei Zhang, Yanbo Li, 2024, original scientific article Abstract: The buried interface tens of nanometers beneath the solid-liquid junction is crucial for photocarrier extraction, influencing the overall efficiency of photoelectrochemical devices. Precise characterization of the interfacial properties is essential for device optimization but remains challenging. Here, we directly probe the in situ transformation of a CuxO interlayer at the NiO/n-Si interface by hard X-ray photoelectron spectroscopy. It is found that Cu(I) in the CuxO interlayer gradually transforms to Cu(II) with air exposure, forming an energetically more favorable interface and improving photoanode’s efficiency. Based on this finding, a reactive e-beam evaporation process is developed for the direct deposition of a CuO interlayer, achieving a half-cell solar-to-hydrogen efficiency of 4.56% for the optimized NiO/CuO/n-Si heterojunction photoanode. Our results highlight the importance of precision characterization of interfacial properties with advanced hard X-ray photoelectron spectroscopy in guiding the design of efficient solar water-splitting devices.
Keywords: photo anode, energy harvesting, nickel oxide, interface
Published in RUNG: 01.08.2024; Views: 1958; Downloads: 12
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5. Air-water interface-assisted synthesis and charge transport characterization of quasi-2d polyacetylene films with enhanced electron mobility via ring-opening polymerization of pyrroleKejun Liu, Nadiia Pastukhova, Egon Pavlica, Gvido Bratina, Xinliang Feng, 2024, other component parts Abstract: Water surfaces catalyze some organic reactions more effectively, making them unique for 2D organic material synthesis. This report introduces a new synthesis method via surfactant-monolayer-assisted interfacial synthesis on water surfaces for ring-opening polymerization of pyrrole, producing distinct polypyrrole derivatives with polyacetylene backbones and ionic substitutions. The synthesis result in quasi 2D polyacetylene (q2DPA) film with enhanced charge transport behavior. We employed time-of-flight photoconductivity (TOFP) measurements using pulsed laser light of tunable wavelength for photoexcitation of the charge carriers within the q2DPA film. The charge transport was measured in the lateral direction as a function of external bias voltage ranging from 0 V to 200 V. We observed high electron mobility ({\mu}) of q2DPA reaching values of 375 cm2 V-1 s-1 at bias voltage Vb = -20V and photon energy of 3.8 eV.
Keywords: air-water interface-assisted synthesis, time-of-flight photoconductivity, 2D polymers, quasi 2D polyacetylene, q2DPA
Published in RUNG: 09.04.2024; Views: 2172; Downloads: 7
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6. Designing atomic interface in ▫$Sb_2S_3/CdS$▫ heterojunction for efficient solar water splittingMinji Yang, Zeyu Fan, Jinyan Du, Chao Feng, Ronghua Li, Beibei Zhang, Nadiia Pastukhova, Matjaž Valant, Matjaž Finšgar, Andraž Mavrič, Yanbo Li, 2024, original scientific article Abstract: In the emerging Sb2S3‐based solar energy conversion devices, a CdS buffer layer prepared by chemical bath deposition is commonly used to improve the separation of photogenerated electron‐hole pairs. However, the cation diffusion at the Sb2S3/CdS interface induces detrimental defects but is often overlooked. Designing a stable interface in the Sb2S3/CdS heterojunction is essential to achieve high solar energy conversion efficiency. As a proof of concept, this study reports that the modification of the Sb2S3/CdS heterojunction with an ultrathin Al2O3 interlayer effectively suppresses the interfacial defects by preventing the diffusion of Cd2+ cations into the Sb2S3 layer. As a result, a water‐splitting photocathode based on Ag:Sb2S3/Al2O3/CdS heterojunction achieves a significantly improved half‐cell solar‐to‐hydrogen efficiency of 2.78% in a neutral electrolyte, as compared to 1.66% for the control Ag:Sb2S3/CdS device. This work demonstrates the importance of designing atomic interfaces and may provide a guideline for the fabrication of high‐performance stibnite‐type semiconductor‐based solar energy conversion devices.
Keywords: alumina, defect passivation, interface engineering, photoelectrochemical water splitting
Published in RUNG: 11.03.2024; Views: 2188; Downloads: 5
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7. On Karttunen’s "The syntax and semantics of questions"Elena Guerzoni, 2022, independent scientific component part or a chapter in a monograph Abstract: Karttunen’s article on the syntax and semantics of questions is a milestone in the truth-conditional compositional semantics of interrogatives and of verbs that embed them. It is the first comprehensive study of the mapping between the syntax and the interpretation of the three different types of questions (polar, constituent and alternative questions) and presents the first semantic analysis of question-embedding verbs (QEVs henceforth) that assumes the same intensions for matrix and embedded interrogatives. This analysis continues to vastly inspire the ongoing research on the properties of questions and QEVs. This chapter illustrates Karttunen’s theory focusing on those formal details that have been the most influential in subsequent literature. In doing so, however, I will take the liberty to suggest a less than literal rendition of these details, in an attempt to make the discussion more accessible to today’s reader. The main departure that I make here from Karttunen’s 1977 is in the formal framework. Whereas Karttunen adopts Montague’s PTQ, here I will expose his ideas in Heim and Kratzer‘s type driven semantics.
Keywords: interrogatives, questions, syntax-semantics interface, compositionality, wh-movement
Published in RUNG: 20.02.2024; Views: 2196; Downloads: 8
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8. 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: 3245; Downloads: 14
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9. 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: 3543; Downloads: 0
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