Sivis, Murat

[["dc.bibliographiccitation.artnumber","012108"],["dc.bibliographiccitation.issue","1"],["dc.bibliographiccitation.journal","AIP Advances"],["dc.bibliographiccitation.volume","2"],["dc.contributor.author","Broxtermann, Daniel"],["dc.contributor.author","Sivis, Murat"],["dc.contributor.author","Malindretos, Jörg"],["dc.contributor.author","Rizzi, Angela"],["dc.date.accessioned","2018-11-07T09:12:36Z"],["dc.date.available","2018-11-07T09:12:36Z"],["dc.date.issued","2012"],["dc.description.abstract","We have grown 2DEG AlGaN/GaN heterostructures by molecular beam epitaxy (MBE) with electron mobilities up to 21500 cm(2)V(-1)s(-1) at 2 K. In-situ RHEED was applied to optimize different aspects of Ga-rich growth. This paper gives a compact overview of the experimental key aspects that significantly affect the low temperature electron mobility in AlGaN/GaN heterostructures. Growth at the transition towards Ga droplet formation produced the best results. A quantitative analysis of the magnetoresistance confirmes scattering at dislocations as the dominant scattering process at low temperature. Copyright 2012 Author(s). This article is distributed under a Creative Commons Attribution 3.0 Unported License. [doi: 10.1063/1.3679149]"],["dc.description.sponsorship","DFG [SFB 602]"],["dc.identifier.doi","10.1063/1.3679149"],["dc.identifier.fs","590413"],["dc.identifier.isi","000302225400026"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/9558"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/26975"],["dc.notes.intern","Merged from goescholar"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.relation.issn","2158-3226"],["dc.relation.orgunit","Fakultät für Physik"],["dc.title","MBE growth of high electron mobility 2DEGs in AlGaN/GaN heterostructures controlled by RHEED"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.issue","1"],["dc.bibliographiccitation.journal","Light"],["dc.bibliographiccitation.volume","10"],["dc.contributor.author","Liebtrau, Matthias"],["dc.contributor.author","Sivis, Murat"],["dc.contributor.author","Feist, Armin"],["dc.contributor.author","Lourenço-Martins, Hugo"],["dc.contributor.author","Pazos-Pérez, Nicolas"],["dc.contributor.author","Alvarez-Puebla, Ramon A."],["dc.contributor.author","de Abajo, F. Javier García"],["dc.contributor.author","Polman, Albert"],["dc.contributor.author","Ropers, Claus"],["dc.date.accessioned","2021-06-01T09:41:38Z"],["dc.date.available","2021-06-01T09:41:38Z"],["dc.date.issued","2021"],["dc.description.abstract","The interplay between free electrons, light, and matter offers unique prospects for space, time, and energy resolved optical material characterization, structured light generation, and quantum information processing. Here, we study the nanoscale features of spontaneous and stimulated electron–photon interactions mediated by localized surface plasmon resonances at the tips of a gold nanostar using electron energy-loss spectroscopy (EELS), cathodoluminescence spectroscopy (CL), and photon-induced near-field electron microscopy (PINEM). Supported by numerical electromagnetic boundary-element method (BEM) calculations, we show that the different coupling mechanisms probed by EELS, CL, and PINEM feature the same spatial dependence on the electric field distribution of the tip modes. However, the electron–photon interaction strength is found to vary with the incident electron velocity, as determined by the spatial Fourier transform of the electric near-field component parallel to the electron trajectory. For the tightly confined plasmonic tip resonances, our calculations suggest an optimum coupling velocity at electron energies as low as a few keV. Our results are discussed in the context of more complex geometries supporting multiple modes with spatial and spectral overlap. We provide fundamental insights into spontaneous and stimulated electron-light-matter interactions with key implications for research on (quantum) coherent optical phenomena at the nanoscale."],["dc.identifier.doi","10.1038/s41377-021-00511-y"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/84986"],["dc.language.iso","en"],["dc.notes.intern","DOI-Import GROB-425"],["dc.relation","SFB 1073: Kontrolle von Energiewandlung auf atomaren Skalen"],["dc.relation","SFB 1073 | Topical Area A | A05 Nanoskalige Untersuchung raumzeitlicher Relaxation in heterogenen Systemen mit ultraschneller Transmissionselektronenmikroskopie"],["dc.relation.eissn","2047-7538"],["dc.rights","CC BY 4.0"],["dc.title","Spontaneous and stimulated electron–photon interactions in nanoscale plasmonic near fields"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.subtype","original_ja"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","63"],["dc.bibliographiccitation.journal","Ultramicroscopy"],["dc.bibliographiccitation.lastpage","73"],["dc.bibliographiccitation.volume","176"],["dc.contributor.author","Feist, Armin"],["dc.contributor.author","Bach, Nora"],["dc.contributor.author","da Silva, Nara Rubiano"],["dc.contributor.author","Danz, Thomas"],["dc.contributor.author","Möller, Marcel"],["dc.contributor.author","Priebe, Katharina E."],["dc.contributor.author","Domröse, Till"],["dc.contributor.author","Gatzmann, J. Gregor"],["dc.contributor.author","Rost, Stefan"],["dc.contributor.author","Schauss, Jakob"],["dc.contributor.author","Strauch, Stefanie"],["dc.contributor.author","Bormann, Reiner"],["dc.contributor.author","Sivis, Murat"],["dc.contributor.author","Schäfer, Sascha"],["dc.contributor.author","Ropers, Claus"],["dc.date.accessioned","2018-11-07T10:23:59Z"],["dc.date.accessioned","2020-02-03T09:08:33Z"],["dc.date.available","2018-11-07T10:23:59Z"],["dc.date.available","2020-02-03T09:08:33Z"],["dc.date.issued","2017"],["dc.description.abstract","We present the development of the first ultrafast transmission electron microscope (UTEM) driven by localized photoemission from a field emitter cathode. We describe the implementation of the instrument, the photoemitter concept and the quantitative electron beam parameters achieved. Establishing a new source for ultrafast TEM, the Göttingen UTEM employs nano-localized linear photoemission from a Schottky emitter, which enables operation with freely tunable temporal structure, from continuous wave to femtosecond pulsed mode. Using this emission mechanism, we achieve record pulse properties in ultrafast electron microscopy of 9Å focused beam diameter, 200fs pulse duration and 0.6eV energy width. We illustrate the possibility to conduct ultrafast imaging, diffraction, holography and spectroscopy with this instrument and also discuss opportunities to harness quantum coherent interactions between intense laser fields and free-electron beams."],["dc.identifier.arxiv","1611.05022v1"],["dc.identifier.doi","10.1016/j.ultramic.2016.12.005"],["dc.identifier.isi","000403992200010"],["dc.identifier.pmid","28139341"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/42570"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/62933"],["dc.language.iso","en"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","PUB_WoS_Import"],["dc.relation","SFB 1073: Kontrolle von Energiewandlung auf atomaren Skalen"],["dc.relation","SFB 1073 | Topical Area A | A05 Nanoskalige Untersuchung raumzeitlicher Relaxation in heterogenen Systemen mit ultraschneller Transmissionselektronenmikroskopie"],["dc.relation.eissn","1879-2723"],["dc.relation.issn","0304-3991"],["dc.rights","CC BY-NC-ND 4.0"],["dc.title","Ultrafast transmission electron microscopy using a laser-driven field emitter: Femtosecond resolution with a high coherence electron beam"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.subtype","original_ja"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","01014"],["dc.bibliographiccitation.journal","EPJ Web of Conferences"],["dc.bibliographiccitation.volume","41"],["dc.contributor.author","Sivis, Murat"],["dc.contributor.author","Duwe, M."],["dc.contributor.author","Abel, B."],["dc.contributor.author","Ropers, Claus"],["dc.date.accessioned","2019-07-09T11:40:13Z"],["dc.date.available","2019-07-09T11:40:13Z"],["dc.date.issued","2013"],["dc.description.abstract","We demonstrate nanostructure-enhanced extreme ultraviolet fluorescence from noble gases driven by low-energy, few-cycle light pulses. Despite sufficient local intensities, plasmon-enhanced high harmonic generation is not observed, which follows from the small, nanometer-size coherent source volume."],["dc.identifier.doi","10.1051/epjconf/20134101014"],["dc.identifier.fs","601621"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/10766"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/58116"],["dc.language.iso","en"],["dc.notes.intern","Merged from goescholar"],["dc.relation.issn","2100-014X"],["dc.relation.orgunit","Fakultät für Physik"],["dc.rights","CC BY 3.0"],["dc.rights.access","openAccess"],["dc.title","Plasmonic enhancement of High Harmonic Generation revisited: Predominance of Atomic Line Emission"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","6337"],["dc.bibliographiccitation.issue","1"],["dc.bibliographiccitation.journal","Nature Communications"],["dc.bibliographiccitation.volume","12"],["dc.contributor.author","Zayko, Sergey"],["dc.contributor.author","Kfir, Ofer"],["dc.contributor.author","Heigl, Michael"],["dc.contributor.author","Lohmann, Michael"],["dc.contributor.author","Sivis, Murat"],["dc.contributor.author","Albrecht, Manfred"],["dc.contributor.author","Ropers, Claus"],["dc.date.accessioned","2021-12-01T09:20:51Z"],["dc.date.available","2021-12-01T09:20:51Z"],["dc.date.issued","2021"],["dc.description.abstract","Light-induced magnetization changes, such as all-optical switching, skyrmion nucleation, and intersite spin transfer, unfold on temporal and spatial scales down to femtoseconds and nanometers, respectively. Pump-probe spectroscopy and diffraction studies indicate that spatio-temporal dynamics may drastically affect the non-equilibrium magnetic evolution. Yet, direct real-space magnetic imaging on the relevant timescales has remained challenging. Here, we demonstrate ultrafast high-harmonic nanoscopy employing circularly polarized high-harmonic radiation for real-space imaging of femtosecond magnetization dynamics. We map quenched magnetic domains and localized spin structures in Co/Pd multilayers with a sub-wavelength spatial resolution down to 16 nm, and strobosocopically trace the local magnetization dynamics with 40 fs temporal resolution. Our compact experimental setup demonstrates the highest spatio-temporal resolution of magneto-optical imaging to date. Facilitating ultrafast imaging with high sensitivity to chiral and linear dichroism, we envisage a wide range of applications spanning magnetism, phase transitions, and carrier dynamics."],["dc.description.sponsorship","Open-Access-Publikationsfonds 2022"],["dc.identifier.doi","10.1038/s41467-021-26594-0"],["dc.identifier.pii","26594"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/94287"],["dc.language.iso","en"],["dc.notes.intern","DOI-Import GROB-478"],["dc.relation.eissn","2041-1723"],["dc.rights","CC BY 4.0"],["dc.title","Ultrafast high-harmonic nanoscopy of magnetization dynamics"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.subtype","original_ja"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","044024"],["dc.bibliographiccitation.issue","4"],["dc.bibliographiccitation.journal","Structural Dynamics"],["dc.bibliographiccitation.volume","4"],["dc.contributor.author","Storeck, Gero"],["dc.contributor.author","Vogelgesang, Simon"],["dc.contributor.author","Sivis, Murat"],["dc.contributor.author","Schäfer, Sascha"],["dc.contributor.author","Ropers, Claus"],["dc.date.accessioned","2018-11-07T10:22:24Z"],["dc.date.available","2018-11-07T10:22:24Z"],["dc.date.issued","2017"],["dc.description.abstract","We present the design and fabrication of a micrometer-scale electron gun for the implementation of ultrafast low-energy electron diffraction from surfaces. A multi-step process involving photolithography and focused-ion-beam nanostructuring is used to assemble and electrically contact the photoelectron gun, which consists of a nanotip photocathode in a Schottky geometry and an einzel lens for beam collimation. We characterize the low-energy electron pulses by a transient electric field effect and achieve pulse durations of 1.3 ps at an electron energy of 80 eV. First diffraction images in a backscattering geometry (at 50 eV electron energy) are shown. (C) 2017 Author(s)."],["dc.description.sponsorship","European Research Council (ERC-StG \"ULEED\")"],["dc.identifier.doi","10.1063/1.4982947"],["dc.identifier.isi","000402004800021"],["dc.identifier.pmid","28580366"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/14779"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/42266"],["dc.notes.intern","Merged from goescholar"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","PUB_WoS_Import"],["dc.relation","info:eu-repo/grantAgreement/EC/H2020/639119/EU/Observing structural dynamics at surfaces with Ultrafast Low-Energy Electron Diffraction/ULEED"],["dc.relation.issn","2329-7778"],["dc.relation.orgunit","Fakultät für Physik"],["dc.rights","CC BY 4.0"],["dc.title","Nanotip-based photoelectron microgun for ultrafast LEED"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.issue","1"],["dc.bibliographiccitation.journal","Communications Physics"],["dc.bibliographiccitation.volume","1"],["dc.contributor.author","Sivis, Murat"],["dc.contributor.author","Pazos-Perez, Nicolas"],["dc.contributor.author","Yu, Renwen"],["dc.contributor.author","Alvarez-Puebla, Ramon"],["dc.contributor.author","García de Abajo, F. Javier"],["dc.contributor.author","Ropers, Claus"],["dc.date.accessioned","2019-11-28T10:31:50Z"],["dc.date.available","2019-11-28T10:31:50Z"],["dc.date.issued","2018"],["dc.description.abstract","Highly nonlinear optical processes require high intensities, typically achieved with ultrashort laser pulses, and hence, they were first observed with the advent of picosecond laser technology. An alternative approach for reaching the required field intensities is offered by localized optical resonances in tailored plasmonic nanostructures, enabling the enhancement of a multitude of nonlinear phenomena. However, so far, plasmon-enhanced high-order nonlinear effects have been restricted to experiments involving short-pulsed and ultrafast laser sources. Here, we demonstrate localized three-photon photoemission from chemically synthesized plasmonic gold nanostars under continuous-wave illumination at sub-MWcm−2 incident intensities. Intensity- and polarization-dependent measurements confirm the nonlinearity of the photoemission process and agree with quantum mechanical calculations of the electron yield from nanostar tips with features smaller than 5 nm, which facilitate local intensity enhancement factors exceeding 1000. Our results open up new avenues for the design of accessible nanoscale coherent electron sources, with potential applications in microscopy, spectroscopy, sensing, and signal processing."],["dc.identifier.doi","10.1038/s42005-018-0014-7"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/15452"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/62699"],["dc.language.iso","en"],["dc.notes.intern","Merged from goescholar"],["dc.relation.issn","2399-3650"],["dc.relation.orgunit","Fakultät für Physik"],["dc.rights","CC BY 4.0"],["dc.title","Continuous-wave multiphoton photoemission from plasmonic nanostars"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]