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- ItemDumbbell gold nanoparticle dimer antennas with advanced optical properties(Frankfurt, M. : Beilstein-Institut zur Förderung der Chemischen Wissenschaften, 2018) Herrmann, Janning F.; Höppener, ChristianePlasmonic nanoantennas have found broad applications in the fields of photovoltaics, electroluminescence, non-linear optics and for plasmon enhanced spectroscopy and microscopy. Of particular interest are fundamental limitations beyond the dipolar approximation limit. We introduce asymmetric gold nanoparticle antennas (AuNPs) with improved optical near-field properties based on the formation of sub-nanometer size gaps, which are suitable for studying matter with high-resolution and single molecule sensitivity. These dumbbell antennas are characterized in regard to their far-field and near-field properties and are compared to similar dimer and trimer antennas with larger gap sizes. The tailoring of the gap size down to sub-nanometer length scales is based on the integration of rigid macrocyclic cucurbituril molecules. Stable dimer antennas are formed with an improved ratio of the electromagnetic field enhancement and confinement. This ratio, taken as a measure of the performance of an antenna, can even exceed that exhibited by trimer AuNP antennas composed of comparable building blocks with larger gap sizes. Fluctuations in the far-field and near-field properties are observed, which are likely caused by distinct deviations of the gap geometry arising from the faceted structure of the applied colloidal AuNPs.
- ItemThe influence of partial replacement of Cu with Ga on the corrosion behavior of Ti40Zr10Cu36PD14 metallic glasses(Bristol : IOP Publishing, 2019) Wei, Qi; Gostin, Petre Flaviu; Addison, Owen; Reed, Daniel; Calin, Mariana; Bera, Supriya; Ramasamy, Parthiban; Davenport, AlisonTiZrCuPdGa metallic glasses are under consideration for small dental biomedical implants. There is interest in replacing some of the Cu with Ga to improve the glass-forming ability and biocompatibility. Ti40Zr10Cu36-xPd14Gax (x = 0, 1, 2, 4, 8 and 10 at.%) metallic glasses in rod and ribbon forms were fabricated by mould casting and melt spinning, respectively, and electrochemically tested in a 0.9wt.% NaCl (0.154 M) solution. It has been shown that for both rod and ribbon samples Ga levels up to 8% have no significant effect on passive current density, pitting potential or cathodic reactivity in 0.9% NaCl at 37°C. Different pitting potential and corrosion potential values were found when ribbon and rod samples of the same composition were compared for all compositions apart from the one containing the highest Ga level (10%). This was attributed to structural relaxation occurring as a result of the slower cooling rates during casting rods compared with melt-spinning ribbons. Substitution of Ga for Cu in these metallic glasses therefore expected to have no significant effect on corrosion susceptibility. © The Author(s) 2019.
- ItemCharge transport in organic nanocrystal diodes based on rolled-up robust nanomembrane contacts(Frankfurt, M. : Beilstein-Institut zur Förderung der Chemischen Wissenschaften, 2017-6-19) Bandari, Vineeth Kumar; Varadharajan, Lakshmi; Xu, Longqian; Jalil, Abdur Rehman; Devarajulu, Mirunalini; Siles, Pablo F.; Zhu, Feng; Schmidt, Oliver G.The investigation of charge transport in organic nanocrystals is essential to understand nanoscale physical properties of organic systems and the development of novel organic nanodevices. In this work, we fabricate organic nanocrystal diodes contacted by rolled-up robust nanomembranes. The organic nanocrystals consist of vanadyl phthalocyanine and copper hexadecafluorophthalocyanine heterojunctions. The temperature dependent charge transport through organic nanocrystals was investigated to reveal the transport properties of ohmic and space-charge-limited current under different conditions, for instance, temperature and bias
- ItemLayered manganese bismuth tellurides with GeBi4Te7- and GeBi6Te10-type structures: Towards multifunctional materials(London : RSC Publ., 2019) Souchay, Daniel; Nentwig, Markus; Günther, Daniel; Keilholz, Simon; de Boor, Johannes; Zeugner, Alexander; Isaeva, Anna; Ruck, Michael; Wolter, Anja U.B.; Büchnerde, Bernd; Oeckler, OliverThe crystal structures of new layered manganese bismuth tellurides with the compositions Mn0.85(3)Bi4.10(2)Te7 and Mn0.73(4)Bi6.18(2)Te10 were determined by single-crystal X-ray diffraction, including the use of microfocused synchrotron radiation. These analyses reveal that the layered structures deviate from the idealized stoichiometry of the 12P-GeBi4Te7 (space group P3m1) and 51R-GeBi6Te10 (space group R3m) structure types they adopt. Modified compositions Mn1-xBi4+2x/3Te7 (x = 0.15-0.2) and Mn1-xBi6+2x/3Te10 (x = 0.19-0.26) assume cation vacancies and lead to homogenous bulk samples as confirmed by Rietveld refinements. Electron diffraction patterns exhibit no diffuse streaks that would indicate stacking disorder. The alternating quintuple-layer [M2Te3] and septuple-layer [M3Te4] slabs (M = mixed occupied by Bi and Mn) with 1 : 1 sequence (12P stacking) in Mn0.85Bi4.10Te7 and 2 : 1 sequence (51R stacking) in Mn0.81Bi6.13Te10 were also observed in HRTEM images. Temperature-dependent powder diffraction and differential scanning calorimetry show that the compounds are high-temperature phases, which are metastable at ambient temperature. Magnetization measurements are in accordance with a MnII oxidation state and point at predominantly ferromagnetic coupling in both compounds. The thermoelectric figures of merit of n-type conducting Mn0.85Bi4.10Te7 and Mn0.81Bi6.13Te10 reach zT = 0.25 at 375 °C and zT = 0.28 at 325 °C, respectively. Although the compounds are metastable, compact ingots exhibit still up to 80% of the main phases after thermoelectric measurements up to 400 °C. © The Royal Society of Chemistry 2019.
- ItemOn the Impact of Strained PECVD Oxide Layers on Oxide Precipitation in Silicon(Pennington, NJ : ECS, 2019) Kissinger, G.; Kot, D.; Lisker, M.; Sattler, A.PECVD oxide layers with different layer stress ranging from about −305.2 MPa to 39.9 MPa were deposited on silicon wafers with similar concentration of interstitial oxygen. After a thermal treatment consisting of rapid thermal annealing (RTA) and furnace annealing 780°C 3 h + 1000°C 16 h in nitrogen the profiles of the oxide precipitate density were investigated. Supersaturations of self-interstitials as function of layer stress were determined by adjusting modelling results to measured depth profiles of bulk microdefects. The self-interstitial supersaturation generated by RTA at 1250°C and 1175°C at the silicon/oxide interface is increasing linearly with increasing layer stress. Values for self-interstitial supersaturation determined on deposited oxide layers after RTA at 1250°C and 1175°C are very similar to values published for RTO by Sudo et al. An RTA at 1175°C with a PECVD oxide on top of the wafer is a method to effectively suppress oxygen precipitation in silicon wafers. Nucleation anneals carried out at 650°C for 4 h and 8 h did not show any effect of PECVD oxide layers on oxide precipitate nucleation. © The Author(s) 2019.
- ItemMagnetic Nanoparticle Chains in Gelatin Ferrogels: Bioinspiration from Magnetotactic Bacteria(Weinheim : Wiley-VCH, 2019) Sturm, Sebastian; Siglreitmeier, Maria; Wolf, Daniel; Vogel, Karin; Gratz, Micha; Faivre, Damien; Lubk, Axel; Büchner, Bernd; Sturm, Elena V.; Cölfen, HelmutInspired by chains of ferrimagnetic nanocrystals (NCs) in magnetotactic bacteria (MTB), the synthesis and detailed characterization of ferrimagnetic magnetite NC chain-like assemblies is reported. An easy green synthesis route in a thermoreversible gelatin hydrogel matrix is used. The structure of these magnetite chains prepared with and without gelatin is characterized by means of transmission electron microscopy, including electron tomography (ET). These structures indeed bear resemblance to the magnetite assemblies found in MTB, known for their mechanical flexibility and outstanding magnetic properties and known to crystallographically align their magnetite NCs along the strongest <111> magnetization easy axis. Using electron holography (EH) and angular dependent magnetic measurements, the magnetic interaction between the NCs and the generation of a magnetically anisotropic material can be shown. The electro- and magnetostatic modeling demonstrates that in order to precisely determine the magnetization (by means of EH) inside chain-like NCs assemblies, their exact shape, arrangement and stray-fields have to be considered (ideally obtained using ET). © 2019 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
- ItemCorrection: Electrochemically deposited nanocrystalline InSb thin films and their electrical properties (Journal of Materials Chemistry C (2016) 4 (1345-1350) DOI: 10.1039/C5TC03656A)(London : RSC Publ., 2019) Hnida, K.E.; Bäßler, S.; Mech, J.; Szaciłowski, K.; Socha, R.P.; Gajewska, M.; Nielsch, K.; Przybylski, M.; Sulka, G.D.There was an error in eqn (3) which was reproduced from the literature and used for the interpretation of the results. The calculations (using the equations from an original work from 1987) were done according the correct version of eqn (3) presented below:. (Table Presented). © 2019 The Royal Society of Chemistry.
- ItemShallow and Undoped Germanium Quantum Wells: A Playground for Spin and Hybrid Quantum Technology(Weinheim : Wiley-VCH, 2019) Sammak, Amir; Sabbagh, Diego; Hendrickx, Nico W.; Lodari, Mario; Wuetz, Brian Paquelet; Tosato, Alberto; Yeoh, LaReine; Bollani, Monica; Virgilio, Michele; Schubert, Markus Andreas; Zaumseil, Peter; Capellini, Giovanni; Veldhorst, Menno; Scappucci, GiordanoBuried-channel semiconductor heterostructures are an archetype material platform for the fabrication of gated semiconductor quantum devices. Sharp confinement potential is obtained by positioning the channel near the surface; however, nearby surface states degrade the electrical properties of the starting material. Here, a 2D hole gas of high mobility (5 × 10 5 cm 2 V −1 s −1 ) is demonstrated in a very shallow strained germanium (Ge) channel, which is located only 22 nm below the surface. The top-gate of a dopant-less field effect transistor controls the channel carrier density confined in an undoped Ge/SiGe heterostructure with reduced background contamination, sharp interfaces, and high uniformity. The high mobility leads to mean free paths ≈ 6 µm, setting new benchmarks for holes in shallow field effect transistors. The high mobility, along with a percolation density of 1.2 × 10 11 cm −2 , light effective mass (0.09m e ), and high effective g-factor (up to 9.2) highlight the potential of undoped Ge/SiGe as a low-disorder material platform for hybrid quantum technologies. © 2019 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
- ItemCorrection: Interface-engineered reliable HfO2-based RRAM for synaptic simulation (Journal of Materials Chemistry C (2019) DOI: 10.1039/c9tc04880d)(London [u.a.] : RSC, 2019) Wang, Qiang; Niu, Gang; Roy, Sourav; Wang, Yankun; Zhang, Yijun; Wu, Heping; Zhai, Shijie; Bai, Wei; Shi, Peng; Song, Sannian; Song, Zhitang; Xie, Ya-Hong; Ye, Zuo-Guang; Wenger, Christian; Meng, Xiangjian; Ren, WeiThere was an error in the author list of this published article. The corresponding authors for this paper are Gang Niu (gangniu@xjtu.edu.cn) and Wei Ren (wren@mail.xjtu.edu.cn). The footnote indicating that Qiang Wang and Gang Niu contributed equally to the work was not intended. The corrected author list and notations are shown here. The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers. © The Royal Society of Chemistry 2019.
- ItemBoundary conditions for electrochemical interfaces(Bristol : IOP Publishing, 2017) Landstorfer, ManuelConsistent boundary conditions for electrochemical interfaces, which cover double layer charging, pseudo-capacitive effects and transfer reactions, are of high demand in electrochemistry and adjacent disciplines. Mathematical modeling and optimization of electrochemical systems is a strongly emerging approach to reduce cost and increase efficiency of super-capacitors, batteries, fuel cells, and electro-catalysis. However, many mathematical models which are used to describe such systems lack a real predictive value. Origin of this shortcoming is the usage of oversimplified boundary conditions. In this work we derive the boundary conditions for some general electrode-electrolyte interface based on non-equilibrium thermodynamics for volumes and surfaces. The resulting equations are widely applicable and cover also tangential transport. The general framework is then applied to a specific material model which allows the deduction of a current-voltage relation and thus a comparison to experimental data. Some simplified 1D examples show the range of applicability of the new approach.