Prof. Dr. rer. nat. Saskia F. Fischer

Profil

• Ballistischer Wärmetransport in dünnen Oxidschichten

  Quelle ↗

  Förderer: DFG Sachbeihilfe Zeitraum: 11/2021 - 10/2025 Projektleitung: Prof. Dr. rer. nat. Saskia F. Fischer

• DFG-NSF-Materials World Network: Spin-Effekte in quasi-1D Systemen in Halbleitern mit niedriger Bandlücke (I)

  Quelle ↗

  Förderer: DFG Sachbeihilfe Zeitraum: 01/2011 - 10/2014 Projektleitung: Prof. Dr. rer. nat. Saskia F. Fischer

• DFG-Sachbeihilfe/1: Untersuchung von Adsorptions- und Desorptionsprozessen auf beta-Ga2O3- und In2O3-Oberflächen mittels Struktur- und thermoelektrischen Analysen

  Quelle ↗

  Förderer: DFG Eigene Stelle (Sachbeihilfe) Zeitraum: 12/2016 - 12/2020 Projektleitung: Prof. Dr. rer. nat. Saskia F. Fischer

• DFG-Sachbeihilfe/2: Untersuchung von Adsorptions- und Desorptionsprozessen auf beta-Ga2O3- und In2O3-Oberflächen mittels Struktur- und thermoelektrischen Analysen

  Quelle ↗

  Förderer: DFG Sachbeihilfe Zeitraum: 01/2017 - 12/2020 Projektleitung: Prof. Dr. rer. nat. Saskia F. Fischer, PD Dr. Marco Busch

• DFG-Sachbeihilfe: Ballistischer Wärmetransport in dünnen und ultradünnen Oxidschichten

  Quelle ↗

  Förderer: DFG Sachbeihilfe Zeitraum: 12/2016 - 06/2020 Projektleitung: Prof. Dr. rer. nat. Saskia F. Fischer

• GraFOx: Thermal and Charge Transport in Bulk and Low-Dimensional Layers

  Quelle ↗

  Förderer: Leibniz-Gemeinschaft Zeitraum: 09/2016 - 08/2020 Projektleitung: Prof. Dr. rer. nat. Saskia F. Fischer

• Leibniz WissenschaftsCampus: Growth and Fundamentals of Oxides for Electronic Applications (GraFOx)

  Quelle ↗

  Förderer: Leibniz-Gemeinschaft Zeitraum: 07/2016 - 12/2019 Projektleitung: Prof. Dr. rer. nat. Saskia F. Fischer, Ph. D. Prof. W. Ted Masselink, Prof. Dr. Dr. h.c. Claudia Draxl

• Leibniz WissenschaftsCampus: Growth and Fundamentals of Oxides for Electronic Applications (GraFOx): Teilprojekt Masselink

  Quelle ↗

  Zeitraum: 07/2016 - 07/2020 Projektleitung: Ph. D. Prof. W. Ted Masselink, Prof. Dr. rer. nat. Saskia F. Fischer, Prof. Dr. Dr. h.c. Claudia Draxl

• Nanodraht-Thermoelektrika mittels Bismuth-basierten Heterostrukturen

  Quelle ↗

  Förderer: Bundesministerium für Forschung, Technologie und Raumfahrt Zeitraum: 06/2017 - 05/2019 Projektleitung: Prof. Dr. rer. nat. Saskia F. Fischer

• Projektlabor Wissenschaftskommunikation (project-sci.com)

  Quelle ↗

  Förderer: Berlin University Alliance (BUA) Zeitraum: 07/2021 - 06/2024 Projektleitung: Prof. Dr. rer. nat. Saskia F. Fischer

• SPP 1285: Spin-Dependent Electron in GaAs/AlGaAs Nanostructures (III)

  Quelle ↗

  Förderer: DFG Sachbeihilfe Zeitraum: 10/2011 - 07/2014 Projektleitung: Prof. Dr. rer. nat. Saskia F. Fischer

• SPP1285: Spin-dependent electron transport in GaAs/AlGaAs nanostructures (II)

  Quelle ↗

  Förderer: DFG Sachbeihilfe Zeitraum: 05/2011 - 01/2012 Projektleitung: Prof. Dr. rer. nat. Saskia F. Fischer

• SPP 1386: Controlled Thermoelectric Properties of Low-Dimensional Charge Carrier Systems in Semiconductor Heterostructures (I)

  Quelle ↗

  Förderer: DFG Sachbeihilfe Zeitraum: 08/2011 - 12/2012 Projektleitung: Prof. Dr. rer. nat. Saskia F. Fischer

• SPP 1386: Controlled thermoelectric properties of low-dimensional charge carrier systems in semiconductor heterostructures (II)

  Quelle ↗

  Förderer: DFG Schwerpunktprogramm Zeitraum: 11/2012 - 07/2016 Projektleitung: Prof. Dr. rer. nat. Saskia F. Fischer

• SPP1386: Structural and thermoelectric characterization of individual single-crystalline nanowires (I)

  Quelle ↗

  Förderer: DFG Sachbeihilfe Zeitraum: 05/2011 - 04/2012 Projektleitung: Prof. Dr. rer. nat. Saskia F. Fischer

• SPP1386: Structural and thermoelectric characterization of individual single-crystalline nanowires (II)

  Quelle ↗

  Förderer: DFG Sachbeihilfe Zeitraum: 11/2012 - 12/2015 Projektleitung: Prof. Dr. rer. nat. Saskia F. Fischer

• SPP 1666/1: Magnetically Doped Topological Insulators: Surfaces States, Dimensionality and Defect Effects

  Quelle ↗

  Förderer: DFG Schwerpunktprogramm Zeitraum: 08/2013 - 07/2018 Projektleitung: Prof. Dr. rer. nat. Saskia F. Fischer

• SPP 1666/2: Magnetisch dotierte topologische Isolatoren: Vom Grundzustand zur Dynamik

  Quelle ↗

  Förderer: DFG Schwerpunktprogramm Zeitraum: 01/2017 - 01/2020 Projektleitung: Prof. Dr. rer. nat. Saskia F. Fischer

• InnovationLab GmbH

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  103 Treffer62.0%
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    62.0%

• ON Semiconductor Belgium BVBA

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• NXP Semiconductors Netherlands BV

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• ACCO SAS

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• Bernstein Center for Computational Neuroscience Berlin

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    58.0%
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• Science & Startups Berlin

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  • Zuwendung im Rahmen des Programms „exist – Existenzgründungen aus der Wissenschaft“ aus dem Bundeshaushalt, Einzelplan 09, Kapitel 02, Titel 68607, Haushaltsjahr 2026, sowie aus Mitteln des Europäischen Strukturfonds (hier Euro-päischer Sozialfonds Plus – ESF Plus) Förderperiode 2021-2027 – Kofinanzierung für das Vorhaben: „exist Women“
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• Peugeot Citroen Automobiles S.A.

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• Ionera Technologies GmbH

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• SoftBank Robotics

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• NELA Brüder Neumeister GmbH

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• Hexagonally ordered 100 nm period nickel nanowire arrays

  2001

  Applied Physics Letters · 542 Zitationen · DOI

  The magnetic behavior of 100 nm period arrays of Ni nanowires embedded in a highly ordered alumina pore matrix were characterized by magnetometry and magnetic force microscopy. Reducing the diameter of the nanowires from 55 to 30 nm while keeping the interwire distance constant leads to increasing coercive fields from 600 to 1200 Oe and to increasing remanence from 30% to 100%. The domain structure of the arrays exhibits in the demagnetized state a labyrith-like pattern. These results show that stray field interactions of single domain nanowires are entirely dependent on the nanowire diameter.

• High density hexagonal nickel nanowire array

  2002

  Journal of Magnetism and Magnetic Materials · 141 Zitationen · DOI

• Temperature-dependent thermal conductivity in Mg-doped and undoped<i>β</i>-Ga₂O₃bulk-crystals

  2015

  Semiconductor Science and Technology · 102 Zitationen · DOI

  For $\beta$-$\mathrm{Ga_2O_3}$ only little information exist concerning the thermal properties, especially the thermal conductivity $\lambda$. Here, the thermal conductivity is measured by applying the electrical 3$\omega$-method on Czochralski-grown $\beta$-$\mathrm{Ga_2O_3}$ bulk crystals, which have a thickness of $200~\mathrm{\mu m}$ and $800~\mathrm{\mu m}$. At room temperature the thermal conductivity along the [100]-direction in Mg-doped electrical insulating and undoped semiconducting $\beta$-$\mathrm{Ga_2O_3}$ is confirmed as $13\pm 1~\mathrm{Wm^{-1}K^{-1}}$ for both crystals. The thermal conductivity increases for decreasing temperature down to $25~\mathrm{K}$ to $\lambda(25~\mathrm{K})=(5.3\pm 0.6)\cdot 10^2~\mathrm{Wm^{-1}K^{-1}}$. The phonon contribution of $\lambda$ dominates over the electron contribution below room temperature. The observed function $\lambda(T)$ is in accord with phonon-phonon-Umklapp scattering and the Debye-model for the specific heat at $T\gtrsim 90~\mathrm{K}$ which is about $0.1$ fold of the Debye-temperature $\theta_\mathrm{D}$. Here a detailed discussion of the phonon-phonon-Umklapp scattering for $T< \theta_\mathrm{D}$ is carried out. The influence of point defect scattering is considered for $T<100~\mathrm{K}$.

• Temperature-dependent thermoelectric properties of individual silver nanowires

  2015

  Physical Review B · 93 Zitationen · DOI

  Individual highly pure single-crystalline silver nanowires (Ag NWs) were investigated with regard to the electrical conductivity $\ensuremath{\sigma}$, the thermal conductivity $\ensuremath{\lambda}$, and the Seebeck coefficient $S$ as a function of the temperature $T$ between $1.4\phantom{\rule{0.28em}{0ex}}\mathrm{K}$ and room temperature (RT). Transmission electron microscopy was performed subsequently to the thermoelectric characterization of the Ag NWs, so that their transport properties can be correlated with the structural data. The crystal structure, surface morphology and the rare occurrence of kinks and twinning were identified. The thermoelectric properties of the Ag NWs are discussed in comparison to the bulk: ${S}_{\mathrm{Ag},\mathrm{Pt}}(T)$ was measured with respect to platinum and is in agreement with the bulk, while $\ensuremath{\sigma}(T)$ and $\ensuremath{\lambda}(T)$ showed reduced values with respect to the bulk. The latter are both notably dominated by surface scattering caused by an increased surface-to-volume ratio. By lowering $T$, the electron mean free path strongly exceeds the NW's diameter of 150 nm so that the transition from diffusive transport to quasiballistic one-dimensional transport is observed. An important result of this work is that the Lorenz number $L(T)$ turns out to be independent of surface scattering. Instead, the characteristic of $L(T)$ is determined by the material's purity. Moreover, $\ensuremath{\sigma}(T)$ and $L(T)$ can be described by the bulk Debye temperature of silver. A detailed discussion of the temperature dependence of $L(T)$ and the scattering mechanisms is given.

• Switching behavior of single nanowires inside dense nickel nanowire arrays

  2002

  IEEE Transactions on Magnetics · 75 Zitationen · DOI

  We report on the micromagnetic properties of highly regular hexagonal arrays of Ni nanowires, fabricated by means of electrodeposition in self-ordered porous alumina. Arrays with interpore distances of 65 and 100 nm and pore diameters of 25 and 30 nm are investigated. From hysteresis loops obtained from measurements with a superconducting quantum interference device (SQUID) magnetometer, the switching field H/sub sw/ of the nanowires and its deviation /spl Delta/H/sub sw/ is derived. Dynamic micromagnetic modeling using the finite-element method is applied to study the reversal process in an external field. It is shown that starting at the wires' ends, the reversal occurs by means of 180/spl deg/ head-on domain walls propagating along the wire.

• Energy spectroscopy of controlled coupled quantum-wire states

  2006

  Nature Physics · 58 Zitationen · DOI

• Suppressing a Charge Density Wave by Changing Dimensionality in the Ferecrystalline Compounds ([SnSe]_1.15)₁(VSe₂)_<i>n</i> with <i>n</i> = 1, 2, 3, 4

  2014

  Nano Letters · 45 Zitationen · DOI

  The compounds, ([SnSe]1.15)1(VSe2)n with n = 1, 2, 3, and 4, were prepared using designed precursors in order to investigate the influence of the thickness of the VSe2 constituent on the charge density wave transition. The structure of each of the compounds was determined using X-ray diffraction and scanning transmission electron microscopy. The charge density wave transition observed in the resistivity of ([SnSe]1.15)1(VSe2)1 was confirmed. The electrical properties of the n = 2 and 3 compounds are distinctly different. The magnitude of the resistivity change at the transition temperature is dramatically lowered and the temperature of the resistivity minimum systematically increases from 118 K (n = 1) to 172 K (n = 3). For n = 1, this temperature correlates with the onset of the charge density wave transition. The Hall-coefficient changes sign when n is greater than 1, and the temperature dependence of the Hall coefficient of the n = 2 and 3 compounds is very similar to the bulk, slowly decreasing as the temperature is decreased, while for the n = 1 compound the Hall coefficient increases dramatically starting at the onset of the charge density wave. The transport properties suggest an abrupt change in electronic properties on increasing the thickness of the VSe2 layer beyond a single layer.

• Synthesis, structure and electrical properties of a new tin vanadium selenide

  2013

  Journal of Solid State Chemistry · 45 Zitationen · DOI

• Intragrain charge transport in kesterite thin films—Limits arising from carrier localization

  2016

  Journal of Applied Physics · 37 Zitationen · DOI

  Intragrain charge carrier mobilities measured by time-resolved terahertz spectroscopy in state of the art Cu2ZnSn(S,Se)4 kesterite thin films are found to increase from 32 to 140 cm2 V−1 s−1 with increasing Se content. The mobilities are limited by carrier localization on the nanometer-scale, which takes place within the first 2 ps after carrier excitation. The localization strength obtained from the Drude-Smith model is found to be independent of the excited photocarrier density. This is in accordance with bandgap fluctuations as a cause of the localized transport. Charge carrier localization is a general issue in the probed kesterite thin films, which were deposited by coevaporation, colloidal inks, and sputtering followed by annealing with varying Se/S contents and yield 4.9%–10.0% efficiency in the completed device.

• Synthesis and Systematic Trends in Structure and Electrical Properties of [(SnSe)_1.15]_<i>m</i>(VSe₂)₁, <i>m</i> = 1, 2, 3, and 4

  2014

  Chemistry of Materials · 35 Zitationen · DOI

  Four compounds [(SnSe)1.15]m(VSe2)1, where m = 1–4, were synthesized to explore the effect of increasing the distance between Se–V–Se dichalcogenide layers on electrical transport properties. These kinetically stable compounds were prepared using designed precursors that contained a repeating pattern of elemental layers with the nanoarchitecture of the desired product. XRD and STEM data revealed that the precursors self-assembled into the desired compounds containing a Se–V–Se dichalcogenide layer precisely separated by a SnSe layer. The 00l diffraction data are used to determine the position of the Sn, Se, and V planes along the c-axis, confirming that the average structure is similar to that observed in the STEM images, and the resulting data agrees well with results obtained from calculations based on density functional theory and a semiempirical description of van der Waals interactions. The in-plane diffraction data contains reflections that can be indexed as hk0 reflections coming from the two independent constituents. The SnSe layers diffract independently from one another and are distorted from the bulk structure to lower the surface free energy. All of the samples showed metallic-like behavior in temperature-dependent resistivity between room temperature and about 150 K. The electrical resistivity systematically increases as m increases. Below 150 K the transport data strongly indicates a charge density wave transition whose onset temperature systematically increases as m increases. This suggests increasing quasi-two-dimensional behavior as increasingly thick layers of SnSe separate the Se–V–Se layers. This is supported by electronic structure calculations.

• Enhanced magneto-thermoelectric power factor of a 70 nm Ni-nanowire

  2012

  Journal of Applied Physics · 35 Zitationen · DOI

  Thermoelectric (TE) properties of a single nanowire (NW) are investigated in a microlab which allows the determination of the Seebeck coefficient S, the electrical conductivity σ, and a full ZT-characterization in the validity limit of the Wiedemann-Franz-law (ZT—figure of merit). A significant influence of the magnetization of a 70 nm diameter ferromagnetic Ni-NW on its power factor S2σ is observed. We detected a strong magnetothermopower effect (MTP) of about 10% and an anisotropic magnetoresistance (AMR) as a function of an external magnetic field B in the order of 1%. At T = 295 K and B = 0 T, we determined the absolute value of S = −(19 ± 2) μV/K. The thermopower S increases considerably as a function of B up to 10% at B = 0.5 T, and with a magnetothermopower of ∂S/∂B ≈ −(3.8 ± 0.5) μV/(KT). The AMR and MTP are related by ∂s/∂r ≈ −11 ± 1 (∂s = ∂S/S). Hence, the TE efficiency increases in a transversal magnetic field (B = 0.5 T) due to an enhanced power factor by nearly 20%.

• High-temperature quantum oscillations of the Hall resistance in bulk Bi₂Se₃.

  2018

  PubMed · 34 Zitationen · DOI

  Helically spin-polarized Dirac fermions (HSDF) in protected topological surface states (TSS) are of high interest as a new state of quantum matter. In three-dimensional (3D) materials with TSS, electronic bulk states often mask the transport properties of HSDF. Recently, the high-field Hall resistance and low-field magnetoresistance indicate that the TSS may coexist with a layered two-dimensional electronic system (2DES). Here, we demonstrate quantum oscillations of the Hall resistance at temperatures up to 50 K in nominally undoped bulk Bi₂Se₃ with a high electron density n of about 2·10¹⁹ cm^-3. From the angular and temperature dependence of the Hall resistance and the Shubnikov-de Haas oscillations we identify 3D and 2D contributions to transport. Angular resolved photoemission spectroscopy proves the existence of TSS. We present a model for Bi₂Se₃ and suggest that the coexistence of TSS and 2D layered transport stabilizes the quantum oscillations of the Hall resistance.

• Porous Nanostructures and Thermoelectric Power Measurement of Electro-Less Etched Black Silicon

  2012

  The Journal of Physical Chemistry C · 33 Zitationen · DOI

  We report the morphology evolution of porous silicon nanostructures and thermoelectric characterization of silicon nanowires (SiNWs) of Electro-Less Etched (ELE) black silicon. Along the axial direction of NWs, the nanopore density (porosity) increases gradually for both highly doped n-Si (n+-Si) and highly doped p-Si (p+-Si). The porosity of silicon nanostructures has been demonstrated to be determined mostly by the wafer doping level and etching time. The formation of porous n+-SiNWs and porous n++-Si film can be understood by an enhanced electron tunnelling from the silicon to the electrolyte through a narrowed space charge layer, while the porous p+-SiNW formation could be the result of an increased thermionic emission current over a lower barrier due to a lower band bending. With microfabricated heaters and thermometers, we measured simultaneously electrical resistivity and thermoelectric power (TEP) of boron-doped SiNWs prepared from a Si wafer with resistivity of 0.2–0.4 Ω cm. The electrical conductivity of NWs indicates an increased role of conducting surface states in the ELE SiNWs with a negligible role of surface scattering. The TEP values of NWs at room temperature are around 1.2 ± 0.1 mV/K, which is comparable to the values of bulk silicon for a similar range of dopant concentration.

• Temperature‐dependent electrical characterization of exfoliated <i>β</i>‐Ga₂O₃ micro flakes

  2014

  physica status solidi (a) · 31 Zitationen · DOI

  Among the transparent semiconducting oxides β ‐Ga 2 O 3 is of high interest because of its wide‐band gap of 4.8 eV and the corresponding transparency from deep ultraviolet to near infrared spectra. Here, we report on the preparation, structural and temperature‐dependent electrical characterization of thin β‐ Ga 2 O 3 micro flakes. β ‐Ga 2 O 3 single crystals are grown using Czochralski technique. Micro flakes are prepared via exfoliation technique in the thickness range from 2.4 to 300 nm. The samples are characterized using confocal microscopy, atomic force microscopy, scanning electron microscopy and transmission electron microscopy. Transport investigations of β ‐Ga 2 O 3 micro flakes are performed in the temperature range from 30 to 300 K. The electrical parameters of flakes with thicknesses larger than 100 nm correspond to those of the source bulk single crystals of highest purity and mobility. The electrical resistivity at room temperature amounts to ρ (293 K) = (1.5 ± 0.5) Ω cm. The temperature‐dependent resistivity has a minimum at T = 130 K of about ρ (130 K) ∼ 1 Ω cm. This finds an explanation in the maximum of the bulk mobility. From the increase of ρ ( T ) between 130 and 300 K we determine an activation energy of E a = (−10.5 ± 0.4) meV. For temperatures below 50 K ρ ( T ) increases indicating a freeze‐out of charge carriers. The non‐alloyed Ti/ β ‐Ga 2 O 3 metal‐semiconductor contact resistance grows inverse with temperature as expected for thermionic emission. At room temperature the Ti/ β ‐Ga 2 O 3 contact resistance is comparable to the resistance of the flake for low current densities of j &lt; 100 A cm −2 . However, at high current densities j &gt; 100 A cm −2 this contact resistance is negligible.

• Structural and Electrical Properties of ([SnSe]_1+δ)_<i>m</i>(NbSe₂)₁ Compounds: Single NbSe₂ Layers Separated by Increasing Thickness of SnSe

  2015

  Chemistry of Materials · 29 Zitationen · DOI

  The compounds ([SnSe]1+δ)m(NbSe2)1, where 1 ≤ m ≤ 10, were prepared from a series of designed precursors. The c-axis lattice parameter systematically increases by 0.577(5) nm as the value of m is increased, which indicates that an additional bilayer of rock salt structured SnSe is inserted for each unit of m. The in-plane structure of both constituents systematically changes as the thickness of SnSe increases. Both X-ray diffraction and electron microscopy studies show the presence of turbostratic disorder between the different constituent layers. The electrical resistivity and Hall coefficient increase systematically as a function of m stronger than would be expected for noninteracting metallic NbSe2 and semiconducting SnSe layers, suggesting the presence of charge transfer between the layers. The temperature dependence of the resistivity changes from metallic behavior for m < 4 to weakly increasing, for higher m, as temperature decreases. Compounds with m > 3 show an upturn in the resistivity below 50 K and a corresponding increase in the Hall coefficient, which both become more pronounced as m increases. This suggests localization of carriers, which is expected in two-dimensional crystals. The extent of charge transfer in ([SnSe]1+δ)m(NbSe2)1 can be tuned as a function of SnSe thickness and spans over the same range as reported in the literature for various NbX2 based intercalated and misfit layer compounds.

• Nanometrology: Absolute Seebeck coefficient of individual silver nanowires

  2019

  Scientific Reports · 28 Zitationen · DOI

  Thermoelectric phenomena can be strongly modified in nanomaterials. The determination of the absolute Seebeck coefficient is a major challenge for metrology with respect to micro- and nanostructures due to the fact that the transport properties of the bulk material are no more valid. Here, we demonstrate a method to determine the absolute Seebeck coefficient S of individual metallic nanowires. For highly pure and single crystalline silver nanowires, we show the influence of nanopatterning on S in the temperature range between 16 K and 300 K. At room temperature, a nanowire diameter below 200 nm suppresses S by 50% compared to the bulk material to less than S = 1 μVK^-1, which is attributed to the reduced electron mean free path. The temperature dependence of the absolute Seebeck coefficient depends on size effects. Thermodiffusion and phonon drag are reduced with respect to the bulk material and the ratio of electron-phonon to phonon-phonon interaction is significantly increased.

• Synthesis of Inorganic Structural Isomers By Diffusion‐Constrained Self‐Assembly of Designed Precursors: A Novel Type of Isomerism

  2014

  Angewandte Chemie International Edition · 27 Zitationen · DOI

  The structure of precursors is used to control the formation of six possible structural isomers that contain four structural units of PbSe and four structural units of NbSe2: [(PbSe)1.14]4[NbSe2]4, [(PbSe)1.14]3[NbSe2]3[(PbSe)1.14]1[NbSe2]1, [(PbSe)1.14]3[NbSe2]2[(PbSe)1.14]1[NbSe2]2, [(PbSe)1.14]2[NbSe2]3[(PbSe)1.14]2[NbSe2]1, [(PbSe)1.14]2[NbSe2]2[(PbSe)1.14]1[NbSe2]1[(PbSe)1.14]1[NbSe2]1, [(PbSe)1.14]2[NbSe2]1[(PbSe)1.14]1[NbSe2]2[(PbSe)1.14]1[NbSe2]1. The electrical properties of these compounds vary with the nanoarchitecture. For each pair of constituents, over 20,000 new compounds, each with a specific nanoarchitecture, are possible with the number of structural units equal to 10 or less. This provides opportunities to systematically correlate structure with properties and hence optimize performance.

• Nonlocal Aharonov–Bohm conductance oscillations in an asymmetric quantum ring

  2009

  Applied Physics Letters · 27 Zitationen · DOI

  We investigate ballistic transport and quantum interference in a nanoscale quantum wire loop fabricated as a GaAs/AlGaAs field-effect heterostructure. Four-terminal measurements of current and voltage characteristics as a function of top gate voltages show negative bend resistance as a clear signature of ballistic transport. In perpendicular magnetic fields, phase-coherent transport leads to Aharonov–Bohm conductance oscillations, which show equal amplitudes in the local and the nonlocal measurement at a temperature of 1.5 K and above. We attribute this observation to the symmetry of the orthogonal cross junctions connecting the four quantum wire leads with the asymmetric quantum wire ring.

• Structural and electrical properties of a new ([SnSe]1.16)1(NbSe2)1 polytype

  2014

  Journal of Alloys and Compounds · 26 Zitationen · DOI

• Control of the transmission phase in an asymmetric four-terminal Aharonov-Bohm interferometer

  2010

  Physical Review B · 26 Zitationen · DOI

  Phase sensitivity and thermal dephasing in coherent electron transport in quasi-one-dimensional (1D) waveguide rings of an asymmetric four-terminal geometry are studied by magnetotransport measurements. We demonstrate the electrostatic control of the phase in Aharonov-Bohm resistance oscillations and investigate the impact of the measurement circuitry on decoherence. Phase rigidity is broken due to the ring geometry: orthogonal waveguide cross junctions and 1D leads minimize reflections and resonances between leads allowing for a continuous electron transmission phase shift. The measurement circuitry influences dephasing: thermal averaging dominates in the nonlocal measurement configuration while additional influence of potential fluctuations becomes relevant in the local configuration.

• Magnetotransport spectroscopy of spatially coincident coupled electron waveguides

  2005

  Physical Review B · 25 Zitationen · DOI

  Magnetotransport spectroscopy is carried out on quantum point contacts fabricated from a 30-nm-wide square quantum well with two occupied two-dimensional subbands. In this system the spatial region of one-dimensional mode coupling is well defined and the two-dimensional reservoirs do not cause interferences. The magnetodispersions in transversal and longitudinal magnetic fields show crossings and anticrossings of the energy levels of the two one-dimensional subladders depending on the parity of the lateral modes of the wave functions. The influence of the quantum point contact geometry and persistent charging effects on coupling is demonstrated.

• Optimization of magnetostriction, coercive field and magnetic transition temperature in nanocrystalline TbDyFe+Zr/Nb multilayers

  1999

  Journal of Magnetism and Magnetic Materials · 25 Zitationen · DOI

• Influence of processing parameters on the transport properties of quantum point contacts fabricated with an atomic force microscope

  2002

  Semiconductor Science and Technology · 24 Zitationen · DOI

  We describe a reliable technique for fabricating ballistic quantum point contacts (QPCs) with large energy separation between one-dimensional subbands. The technique is based on lithography with an atomic force microscope and wet chemical etching of a GaAs/AlGaAs heterostructure. The high-mobility two-dimensional electron gas located 55 nm below the surface is laterally confined by 20 nm or 50 nm deep grooves with separations ranging between 65–105 nm or 100–185 nm, respectively. The conductance characteristics at T = 4.2 K exhibit clear quasi-plateaux at multiples of 2e2/h. Both the conductance threshold voltage and the plateau widths are directly related to the QPC geometry. The energy separation ΔE1,2 of the lowest subbands is determined from the conductance under nonzero dc drain voltage. Upon reducing the QPC width, ΔE1,2 varies from 6 meV to 15 meV.

• Temperature dependence of the Seebeck coefficient of epitaxial β-Ga2O3 thin films

  2019

  APL Materials · 23 Zitationen · DOI

  The temperature dependence of the Seebeck coefficient of homoepitaxial metal organic vapor phase grown, silicon doped β-Ga2O3 thin films was measured relative to aluminum. For room temperature, we found the relative Seebeck coefficient of Sβ-Ga2O3-Al=(−300±20) µV/K. At high bath temperatures T &amp;gt; 240 K, the scattering is determined by electron-phonon-interaction. At lower bath temperatures between T = 100 K and T = 300 K, an increase in the magnitude of the Seebeck coefficient is explained in the frame of Stratton’s formula. The influence of different scattering mechanisms on the magnitude of the Seebeck coefficient is discussed and compared with Hall measurement results.

• The effect of a distinct diameter variation on the thermoelectric properties of individual Bi_0.39Te_0.61nanowires

  2014

  Semiconductor Science and Technology · 23 Zitationen · DOI

  The reduction of the thermal conductivity induced by nano-patterning is one of the major approaches for tailoring thermoelectric material properties. In particular, the role of surface roughness and morphology is under debate. Here, we choose two individual bismuth telluride nanowires (NWs), one with a strong diameter variation between 190 nm and 320 nm (NW1) and the other of 187 nm diameter with smooth sidewalls (NW2). Both serve as model systems for which bulk properties are expected if surface properties do not contribute. We investigate the role of the diameter variation by means of a combined full-thermoelectrical, structural and chemical characterization. By transmission electron microscopy the structure, chemical composition and morphology were determined after the thermoelectrical investigation. The NWs showed an oriented growth along the direction and the same composition. The Seebeck coefficients of both NWs are comparable to each other. The electrical conductivity of both NWs exceeds the bulk value indicating the presence of a topological surface state. Whereas the thermal conductivity of NW2 compares to the bulk, the thermal conductivity of NW1 is about half of NW2 which is discussed with respect to its distinct diameter variation.

• Freie Universität Berlin

  Projektlabor Wissenschaftskommunikation (project-sci.com)

  university

• Helmholtz-Zentrum Berlin für Materialien und Energie

  SPP 1666/2: Magnetisch dotierte topologische Isolatoren: Vom Grundzustand zur Dynamik

  other

• Leibniz-Institut für Kristallzüchtung, Berlin-Adlershof

  DFG-Sachbeihilfe: Ballistischer Wärmetransport in dünnen und ultradünnen Oxidschichten

  other

• Ludwig-Maximilians-Universität München

  SPP 1666/2: Magnetisch dotierte topologische Isolatoren: Vom Grundzustand zur Dynamik

  university

• Paul-Drude-Institut für Festkörperelektronik, Berlin

  GraFOx: Thermal and Charge Transport in Bulk and Low-Dimensional Layers

  other

• Technische Universität Berlin

  Projektlabor Wissenschaftskommunikation (project-sci.com)

  university

Name

Prof. Dr. rer. nat. Saskia F. Fischer

Titel

Prof. Dr. rer. nat.

Fakultät

Mathematisch-Naturwissenschaftliche Fakultät

Institut

Institut für Physik

Arbeitsgruppe

Neue Materialien

Telefon

+49 30 2093-82202

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26.4.2026, 01:04:43