Showing papers by "Torsten Fritz published in 2022"
TL;DR: In this paper , the authors demonstrate the wafer-scale synthesis of adlayer-free ultra-flat single-crystal monolayer graphene on sapphire substrates and demonstrate the epitaxial growth of graphene at the interface between Cu(111) and Al2O3(0001) by multi-cycle plasma etching assisted chemical vapour deposition.
Abstract: The growth of inch-scale high-quality graphene on insulating substrates is desirable for electronic and optoelectronic applications, but remains challenging due to the lack of metal catalysis. Here we demonstrate the wafer-scale synthesis of adlayer-free ultra-flat single-crystal monolayer graphene on sapphire substrates. We converted polycrystalline Cu foil placed on Al2O3(0001) into single-crystal Cu(111) film via annealing, and then achieved epitaxial growth of graphene at the interface between Cu(111) and Al2O3(0001) by multi-cycle plasma etching-assisted-chemical vapour deposition. Immersion in liquid nitrogen followed by rapid heating causes the Cu(111) film to bulge and peel off easily, while the graphene film remains on the sapphire substrate without degradation. Field-effect transistors fabricated on as-grown graphene exhibited good electronic transport properties with high carrier mobilities. This work breaks a bottleneck of synthesizing wafer-scale single-crystal monolayer graphene on insulating substrates and could contribute to next-generation graphene-based nanodevices.
59 citations
TL;DR: In this article , the influence of the bias value on the properties of HfO2 thin films was analyzed using tetrakis(dimethylamino)cyclopentadienyl hafnium (TDMAH) and oxygen plasma.
Abstract: Tuning ion energies in plasma-enhanced atomic layer deposition (PEALD) processes enables fine control over the material properties of functional coatings. The growth, structural, mechanical, and optical properties of HfO2 thin films are presented in detail toward photonic applications. The influence of the film thickness and bias value on the properties of HfO2 thin films deposited at 100 °C using tetrakis(dimethylamino)hafnium (TDMAH) and oxygen plasma using substrate biasing is systematically analyzed. The HfO2 films deposited without a substrate bias show an amorphous microstructure with a low density, low refractive index, high incorporation of residual hydroxyl (OH) content, and high residual tensile stress. The material properties of HfO2 films significantly improved at a low bias voltage due to the interaction with oxygen ions accelerated to the film. Such HfO2 films have a higher density, higher refractive index, and lower residual OH incorporation than films without bias. The mechanical stress becomes compressive depending on the bias values. Further increasing the ion energies by applying a larger substrate bias results in a decrease of the film density, refractive index, and a higher residual OH incorporation as well as crystalline inclusions. The comparable material properties of the HfO2 films have been reported using tris(dimethylamino)cyclopentadienyl hafnium (TDMACpH) in a different apparatus, indicating that this approach can be transferred to various systems and is highly versatile. Finally, the substrate biasing technique has been introduced to deposit stress-compensated, crack- and delamination-free high-reflective (HR) mirrors at 355 and 532 nm wavelengths using HfO2 and SiO2 as high and low refractive index materials, respectively. Such mirrors could not be obtained without the substrate biasing during the deposition because of the high tensile stress of HfO2, leading to cracks in thick multilayer systems. An HR mirror for 532 nm wavelength shows a high reflectance of 99.93%, a residual transmittance of ∼530 ppm, and a low absorption of ∼11 ppm, as well as low scattering losses of ∼4 ppm, high laser-induced damage threshold, low mechanical stress, and high environmental stability.
4 citations
TL;DR: In this article , a 3,4:9,10-perylenetetetracarboxylic dianhydride (PTCDA) monolayers and multilayer films were constructed on BlueP/Au(111) using in situ optical differential reflectance spectroscopy.
Abstract: Blue phosphorene (BlueP) is considered as a promising two-dimensional (2D) material for future-(opto)electronic applications. Monolayer BlueP is often fabricated on Au(111) single-crystal surfaces. It has been suggested that small P domains form a lateral network with Au adatoms. Previous studies attempting to use BlueP/Au(111) as a substrate for the deposition of fullerene indicated that the former is susceptible to structural deterioration, unlike most other 2D materials in this regard. Here, we investigate 3,4:9,10-perylenetetracarboxylic dianhydride (PTCDA) monolayers and multilayer films deposited on BlueP/Au(111). We monitor the film growth in real time using in situ optical differential reflectance spectroscopy with the substrate kept either at room temperature or at $\ensuremath{\approx}120{\phantom{\rule{0.16em}{0ex}}}^{\ensuremath{\circ}}\mathrm{C}$. Furthermore, we examine the epitaxial alignment between PTCDA and BlueP by means of distortion-corrected low-energy electron diffraction and low-temperature scanning tunneling microscopy. Our data clearly reveal that PTCDA exhibits a highly ordered monolayer structure with a herringbone packing motif, whereas the domain orientations differ from all previously reported structures of PTCDA directly on Au(111). Importantly, we find no indications for adsorption-induced reordering or degradation of BlueP/Au(111). At elevated temperatures, PTCDA is observed to form multilayer islands covering only a fraction of the available PTCDA monolayer surface on BlueP/Au(111), and this Stranski-Krastanov growth mode bears similarities to literature results for PTCDA multilayers on pristine coinage metal surfaces.
2 citations
TL;DR: In this paper , the structural and electronic properties of epitaxial monolayer graphene on SiC(0001) are examined upon potassium intercalation, and the first real-space observation via scanning tunneling microscopy of the (2 × 2) superstructure in graphene-based thin films formed by the potassium atoms below the uppermost graphene layer is presented.
Abstract: The structural and electronic properties of epitaxial monolayer graphene on SiC(0001) are examined upon potassium intercalation. Notably, the first real‐space observation via scanning tunneling microscopy of the (2 × 2) superstructure in graphene‐based thin films formed by the potassium atoms below the uppermost graphene layer is presented. Therein, additional signatures stemming from quasiparticle interference effects are found allowing investigations of the electronic bands of K‐intercalated epitaxial monolayer graphene on a local scale. Those data are compared to area‐averaged results obtained from photoelectron spectroscopy. In particular, backfolding of the graphene π bands are found as a consequence of the (2 × 2) superstructure of the K atoms with respect to the graphene lattice. This is accompanied by a strong n‐type doping effect that causes a rigid shift of the Dirac bands to higher binding energies and filling of two parabolic interlayer bands at the Γ point of the surface Brillouin zone of the graphene lattice as well. This electronic configuration is promoted by additional penetration of potassium atoms into the interspace between the SiC substrate and the buffer layer that is located between the substrate and the quasi‐freestanding graphene sheet. Consequently, the epitaxial monolayer graphene sample transforms to n‐doped epitaxial bilayer graphene upon K intercalation.
1 citations
TL;DR: The Altmetric Attention Score as mentioned in this paper is a quantitative measure of the attention that a research article has received online, and it is calculated using a weighted average of the number of click-throughs on a page at altmetric.com.
Abstract: ADVERTISEMENT RETURN TO ISSUEPREVAddition/CorrectionNEXTORIGINAL ARTICLEThis notice is a correctionCorrection to “Ordered Growth and Electronic Properties of 1,2:8,9-Dibenzopentacene (trans-DBPen) on Ag(111)”Felix OttoFelix OttoInstitut für Festkörperphysik, Friedrich-Schiller-Universität Jena, D-07743 Jena, GermanyMore by Felix Ottohttps://orcid.org/0000-0002-2327-5950, Tobias HuempfnerTobias HuempfnerInstitut für Festkörperphysik, Friedrich-Schiller-Universität Jena, D-07743 Jena, GermanyMore by Tobias Huempfner, Maximilian SchaalMaximilian SchaalInstitut für Festkörperphysik, Friedrich-Schiller-Universität Jena, D-07743 Jena, GermanyMore by Maximilian Schaalhttps://orcid.org/0000-0003-4533-1666, Christian UdhardtChristian UdhardtInstitut für Festkörperphysik, Friedrich-Schiller-Universität Jena, D-07743 Jena, GermanyMore by Christian Udhardt, Lennart VorbrinkLennart VorbrinkInstitut für Festkörperphysik, Friedrich-Schiller-Universität Jena, D-07743 Jena, GermanyMore by Lennart Vorbrink, Bernd SchroeterBernd SchroeterInstitut für Festkörperphysik, Friedrich-Schiller-Universität Jena, D-07743 Jena, GermanyMore by Bernd Schroeter, Roman ForkerRoman ForkerInstitut für Festkörperphysik, Friedrich-Schiller-Universität Jena, D-07743 Jena, GermanyMore by Roman Forkerhttps://orcid.org/0000-0003-0969-9180, and Torsten Fritz*Torsten FritzInstitut für Festkörperphysik, Friedrich-Schiller-Universität Jena, D-07743 Jena, Germany*E-mail: [email protected]More by Torsten Fritzhttps://orcid.org/0000-0001-6904-1909Cite this: J. Phys. Chem. C 2022, 126, 21, 9207Publication Date (Web):May 18, 2022Publication History Published online18 May 2022Published inissue 2 June 2022https://doi.org/10.1021/acs.jpcc.2c02762Copyright © 2022 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views68Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (714 KB) Get e-Alerts Get e-Alerts
16 Dec 2022
TL;DR: In this article , the authors propose a solution to solve the problem of the problem: this article ] of "uniformity" and "uncertainty" of the solution.
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TL;DR: In this article , the correlation of the involved two-and three-dimensional crystallographic lattices was studied experimentally in terms of the correlation between two-dimensional and threedimensional lattices.
Abstract: Organic epitaxy is studied experimentally in terms of the correlation of the involved two- and three-dimensional crystallographic lattices.
TL;DR: In this paper , the assignment of epitaxy types by Wang et al. is critically examined and the crucial distinction between these epitaxial types is discussed, as well as the strain values given by them with subpercent accuracy for monolayers are revisited.
Abstract: The assignment of epitaxy types by Wang et al. [Phys. Rev. B 103, 245430 (2021)] is critically examined. In particular, a ${\mathrm{C}}_{60}$ phase grown on Cd(0001) is denoted by them as ``incommensurate''; however, it is most likely higher order commensurate. The crucial distinction between these epitaxy types is discussed here. Further, the strain values given by Wang et al. with subpercent accuracy for ${\mathrm{C}}_{60}$ monolayers are revisited. Systematic errors are identified due to the unjustified negligence of the temperature dependencies of the involved lattice constants, the largest contribution stemming from the bulk lattice constant of ${\mathrm{C}}_{60}$ used by Wang et al. as a reference value for strain calculations.
TL;DR: In this paper , a novel type of bistable magnetic state of the organic semiconductor HATCN (C 18 N 12 ) on Ag(111) which exhibits Kondo switching was reported.
Abstract: : Molecular Kondo switches have become an important avenue for potential applications in the growing field of molecular spintronics. Here, we report a novel type of bistable magnetic state of the organic semiconductor HATCN (C 18 N 12 ) on Ag(111) which exhibits Kondo switching. Low-temperature scanning tunneling microscopy/spectroscopy (LT-STM/STS) measurements reveal the existence of two types of adsorbed HATCN molecules with distinctly different appearances and magnetic states, as evident from the presence or absence of an Abrikosov-Suhl-Kondo (ASK) resonance. Our DFT results show that HATCN on Ag(111) supports two almost isoenergetic states, both with one excess electron transferred from the Ag surface, but with magnetic moments of either 0 or 0.65 µ B . Therefore, even though all molecules undergo charge transfer of 1 electron from the Ag substrate, they exist in two different molecular magnetic states that resemble a free doublet or an entangled spin state. We show that molecules can be switched to the Kondo state. This study provides deeper insight into the physics of the Kondo effect in molecules on surfaces and explores a molecular Kondo switch potentially suited for practical spintronics.
13 Dec 2022
TL;DR: In this article , the authors introduced the concept of using frontier orbital degeneracy for tailoring the magnetic state, which is demonstrated for the case of the organic semiconductor 1,4,5,8,9,11-Hexaazatriphenylenehexacarbonitrile (HATCN, C18N12) on Ag(111).
Abstract: Kondo resonances in molecular adsorbates are an important building block for applications in the field of molecular spintronics. Here, we introduce the novel concept of using frontier orbital degeneracy for tailoring the magnetic state, which is demonstrated for the case of the organic semiconductor 1,4,5,8,9,11-Hexaazatriphenylenehexacarbonitrile (HATCN, C18N12) on Ag(111). Low-temperature scanning tunneling microscopy/spectroscopy (LT-STM/STS) measurements reveal the existence of two types of adsorbed HATCN molecules with distinctly different appearances and magnetic states, as evident from the presence or absence of an Abrikosov-Suhl-Kondo resonance. Our DFT results show that HATCN on Ag(111) supports two almost isoenergetic states, both with one excess electron transferred from the Ag surface, but with magnetic moments of either 0 or 0.65 uB. Therefore, even though all molecules undergo charge transfer of one electron from the Ag substrate, they exist in two different molecular magnetic states that resemble a free doublet or an entangled spin state. We explain how the origin of this behavior lies in the twofold degeneracy of the lowest unoccupied molecular orbitals of gas phase HATCN, lifted upon adsorption and charge-transfer from Ag(111). Our combined STM and DFT study introduces a new pathway to tailoring the magnetic state of molecular adsorbates on surfaces, with significant potential for spintronics and quantum information science.
TL;DR: A general formalism to determine the surface unit cell of a three-dimensional crystallographic lattice is presented in this article , where the unit cell is defined as the sum of the number of unit cells of the lattice and the length of the cell.
Abstract: A general formalism to determine the surface unit cell of a three-dimensional crystallographic lattice is presented.
TL;DR: In this article , the structural and optical properties of the metal-dielectric interfaces of Ir/Al2O3 heterostructures compatible with micro-optoelectronic technologies are reported.
Abstract: Heterostructures increasingly attracted attention over the past several years to enable various optoelectronic and photonic applications. In this work, atomically thin interfaces of Ir/Al2O3 heterostructures compatible with micro-optoelectronic technologies are reported. Their structural and optical properties were determined by spectroscopic and microscopic techniques (XRR, XPS, HRTEM, spectroscopic ellipsometry, and UV/vis/NIR spectrophotometry). The XRR and HRTEM analyses reveal a layer-by-layer growth mechanism of Ir in atomic scale heterostructures, which is different from the typical island-type growth of metals on dielectrics. Alongside, XPS investigations imply the formation of Ir-O-Al bonding at the interfaces for lower Ir concentrations, in contrast to the nanoparticle core-shell structure formation. Precisely tuning the ratio of the constituents ensures the control of the dispersion profile along with a transition from effective dielectric to metallic heterostructures. The Ir coating thickness was varied ranging from a few angstroms to films of about 7 nm in the heterostructures. The transition has been observed in the structures containing individual Ir coating thicknesses of about 2-4 nm. Following this, we show epsilon-near-zero metamaterials with tunable dielectric constants by precisely varying the composition of such heterostructures. Overall, a comprehensive study on structural and optical properties of the metal-dielectric interfaces of Ir/Al2O3 heterostructures was addressed, indicating an extension of the material portfolio available for novel optical functionalities.