| 1. |
- Carrad, D J, et al.
(författare)
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Hybrid Nanowire Ion-to-Electron Transducers for Integrated Bioelectronic Circuitry
- 2017
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 17:2, s. 827-833
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Tidskriftsartikel (refereegranskat)abstract
- A key task in the emerging field of bioelectronics is the transduction between ionic/protonic and electronic signals at high fidelity. This is a considerable challenge since the two carrier types exhibit intrinsically different physics and are best supported by very different materials types - electronic signals in inorganic semiconductors and ionic/protonic signals in organic or bio-organic polymers, gels, or electrolytes. Here we demonstrate a new class of organic-inorganic transducing interface featuring semiconducting nanowires electrostatically gated using a solid proton-transporting hygroscopic polymer. This model platform allows us to study the basic transducing mechanisms as well as deliver high fidelity signal conversion by tapping into and drawing together the best candidates from traditionally disparate realms of electronic materials research. By combining complementary n- and p-type transducers we demonstrate functional logic with significant potential for scaling toward high-density integrated bioelectronic circuitry.
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| 2. |
- Gluschke, J. G., et al.
(författare)
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Integrated bioelectronic proton-gated logic elements utilizing nanoscale patterned Nafion
- 2021
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Ingår i: Materials Horizons. - : Royal Society of Chemistry (RSC). - 2051-6347 .- 2051-6355. ; 8:1, s. 224-233
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Tidskriftsartikel (refereegranskat)abstract
- A central endeavour in bioelectronics is the development of logic elements to transduce and process ionic to electronic signals. Motivated by this challenge, we report fully monolithic, nanoscale logic elements featuring n- and p-type nanowires as electronic channels that are proton-gated by electron-beam patterned Nafion. We demonstrate inverter circuits with state-of-the-art ion-to-electron transduction performance giving DC gain exceeding 5 and frequency response up to 2 kHz. A key innovation facilitating the logic integration is a new electron-beam process for patterning Nafion with linewidths down to 125 nm. This process delivers feature sizes compatible with low voltage, fast switching elements. This expands the scope for Nafion as a versatile patternable high-proton-conductivity element for bioelectronics and other applications requiring nanoengineered protonic membranes and electrodes.
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| 3. |
- Fatemi, V., et al.
(författare)
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Microwave Susceptibility Observation of Interacting Many-Body Andreev States
- 2022
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Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 129:22
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Tidskriftsartikel (refereegranskat)abstract
- Electrostatic charging affects the many-body spectrum of Andreev states, yet its influence on their microwave properties has not been elucidated. We developed a circuit quantum electrodynamics probe that, in addition to transition spectroscopy, measures the microwave susceptibility of different states of a semiconductor nanowire weak link with a single dominant (spin-degenerate) Andreev level. We found that the microwave susceptibility does not exhibit a particle-hole symmetry, which we qualitatively explain as an influence of Coulomb interaction. Moreover, our state-selective measurement reveals a large, ?-phase shifted contribution to the response common to all many-body states which can be interpreted as arising from a phase-dependent continuum in the superconducting density of states.
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| 4. |
- Nguyen, H. Q., et al.
(författare)
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Electrostatic control of quasiparticle poisoning in a hybrid semiconductor-superconductor island
- 2023
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Ingår i: Physical Review B. - 2469-9950. ; 108:4
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Tidskriftsartikel (refereegranskat)abstract
- The performance of superconducting devices is often degraded by the uncontrolled appearance and disappearance of quasiparticles, a process known as poisoning. We demonstrate the electrostatic control of quasiparticle poisoning in the form of single-charge tunneling across a fixed barrier onto a Coulomb island in an InAs/Al hybrid nanowire. High-bandwidth charge sensing was used to monitor the charge occupancy of the island across Coulomb blockade peaks, where tunneling rates were maximal, and Coulomb valleys, where tunneling was absent. Electrostatic gates changed the on-peak tunneling rates by two orders of magnitude for a barrier with fixed normal-state resistance, which we attribute to the gate dependence of the size and softness of the induced superconducting gap on the island, corroborated by separate density-of-states measurements. Temperature and magnetic field dependence of tunneling rates are also investigated.
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| 5. |
- Bouman, Daniël, et al.
(författare)
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Triplet-blockaded Josephson supercurrent in double quantum dots
- 2020
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Ingår i: Physical Review B. - 2469-9969 .- 2469-9950. ; 102:22
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Tidskriftsartikel (refereegranskat)abstract
- Serial double quantum dots created in semiconductor nanostructures provide a versatile platform for investigating two-electron spin quantum states, which can be tuned by electrostatic gating and an external magnetic field. In this Rapid Communication, we directly measure the supercurrent reversal between adjacent charge states of an InAs nanowire double quantum dot with superconducting leads, in good agreement with theoretical models. In the even charge parity sector, we observe a supercurrent blockade with increasing magnetic field, corresponding to the spin singlet to triplet transition. Our results demonstrate a direct spin to supercurrent conversion, the superconducting equivalent of the Pauli spin blockade. This effect can be exploited in hybrid quantum architectures coupling the quantum states of spin systems and superconducting circuits.
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| 6. |
- Chen, Yan, et al.
(författare)
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Gate-tunable superconductivity in hybrid InSb-Pb nanowires
- 2023
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Ingår i: Applied Physics Letters. - 0003-6951 .- 1077-3118. ; 123:8
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Tidskriftsartikel (refereegranskat)abstract
- We present a report on hybrid InSb-Pb nanowires that combine high spin-orbit coupling with a high critical field and a large superconducting gap. Material characterization indicates the Pb layer of high crystal quality on the nanowire side facets. Hard induced superconducting gaps and gate-tunable supercurrent are observed in the hybrid nanowires. These results showcase the promising potential of this material combination for a diverse range of applications in hybrid quantum transport devices.
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| 7. |
- Deng, M. T., et al.
(författare)
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Majorana bound state in a coupled quantum-dot hybrid-nanowire system
- 2016
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 354:6319, s. 1557-1562
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Tidskriftsartikel (refereegranskat)abstract
- Hybrid nanowires combining semiconductor and superconductor materials appear well suited for the creation, detection, and control of Majorana bound states (MBSs). We demonstrate the emergence of MBSs from coalescing Andreev bound states (ABSs) in a hybrid InAs nanowire with epitaxial Al, using a quantum dot at the end of the nanowire as a spectrometer. Electrostatic gating tuned the nanowire density to a regime of one or a few ABSs. In an applied axial magnetic field, a topological phase emerges in which ABSs move to zero energy and remain there, forming MBSs. We observed hybridization of the MBS with the end-dot bound state, which is in agreement with a numerical model. The ABS/MBS spectra provide parameters that are useful for understanding topological superconductivity in this system.
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| 8. |
- Hays, M., et al.
(författare)
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Coherent manipulation of an Andreev spin qubit
- 2021
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 373:6553, s. 430-433
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Tidskriftsartikel (refereegranskat)abstract
- Two promising architectures for solid-state quantum information processing are based on electron spins electrostatically confined in semiconductor quantum dots and the collective electrodynamic modes of superconducting circuits. Superconducting electrodynamic qubits involve macroscopic numbers of electrons and offer the advantage of larger coupling, whereas semiconductor spin qubits involve individual electrons trapped in microscopic volumes but are more difficult to link. We combined beneficial aspects of both platforms in the Andreev spin qubit: the spin degree of freedom of an electronic quasiparticle trapped in the supercurrent-carrying Andreev levels of a Josephson semiconductor nanowire. We performed coherent spin manipulation by combining single-shot circuit–quantum-electrodynamics readout and spin-flipping Raman transitions and found a spin-flip time TS = 17 microseconds and a spin coherence time T2E = 52 nanoseconds. These results herald a regime of supercurrent-mediated coherent spin-photon coupling at the single-quantum level.
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| 9. |
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| 10. |
- Holmér, Jonatan, 1990, et al.
(författare)
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An STM – SEM setup for characterizing photon and electron induced effects in single photovoltaic nanowires
- 2018
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Ingår i: Nano Energy. - : Elsevier BV. - 2211-2855. ; 53, s. 175-181
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Tidskriftsartikel (refereegranskat)abstract
- Vertical arrays of semiconductor nanowires show great potential for material-efficient and high-performance solar cells. The characterization and correlation between material structure and properties of the individual nanowires are crucial for the continued performance improvement of such devices. In this work, we developed a method with a scanning tunneling microscope (STM) probe inside a scanning electron microscope (SEM) to enable the studies of single photovoltaic nanowires. The STM probe is used to contact individual nanowires in ensembles. We combine the STM-SEM with an in situ light emitting diode (LED) illumination source to study both the electrical and photovoltaic properties of vertical GaAs nanowires with radial p-i-n junctions. We also illustrate that the local charge separation ability within the nanowires can be studied by electron beam induced current (EBIC) measurements. The in situ SEM setup allows the correlation between properties and nanowire structure. The data show that the quality of the electrical contact to the semiconductor nanowire is crucial to be able to investigate the inherent properties of the nanowires. We have established a procedure to make high-quality ohmic contacts to the nanowires with the STM probe. We also show that the effect of mechanical strain on the electrical properties can be investigated by the STM-SEM setup.
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| 11. |
- Holmér, Jonatan, 1990, et al.
(författare)
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Enhancing the NIR Photocurrent in Single GaAs Nanowires with Radial p-i-n Junctions by Uniaxial Strain
- 2021
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 2:21, s. 9038-9043
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Tidskriftsartikel (refereegranskat)abstract
- III-V compound nanowires have electrical and optical properties suitable for a wide range of applications, including photovoltaics and photodetectors. Furthermore, their elastic nature allows the use of strain engineering to enhance their performance. Here we have investigated the effect of mechanical strain on the photocurrent and the electrical properties of single GaAs nanowires with radial p-i-n junctions, using a nanoprobing setup. A uniaxial tensile strain of 3% resulted in an increase in photocurrent by more than a factor of 4 during NIR illumination. This effect is attributed to a decrease of 0.2 eV in nanowire bandgap energy, revealed by analysis of the current-voltage characteristics as a function of strain. This analysis also shows how other properties are affected by the strain, including the nanowire resistance. Furthermore, electron-beam-induced current maps show that the charge collection efficiency within the nanowire is unaffected by strain measured up to 0.9%.
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| 12. |
- Kringhøj, A., et al.
(författare)
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Anharmonicity of a superconducting qubit with a few-mode Josephson junction
- 2018
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Ingår i: Physical Review B. - 2469-9950. ; 97:6
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Tidskriftsartikel (refereegranskat)abstract
- Coherent operation of gate-voltage-controlled hybrid transmon qubits (gatemons) based on semiconductor nanowires was recently demonstrated. Here we experimentally investigate the anharmonicity in epitaxial InAs-Al Josephson junctions, a key parameter for their use as a qubit. Anharmonicity is found to be reduced by roughly a factor of 2 compared to conventional metallic junctions and dependent on gate voltage. Experimental results are consistent with a theoretical model, indicating that Josephson coupling is mediated by a small number of highly transmitting modes in the semiconductor junction.
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| 13. |
- Meyer-Holdt, J., et al.
(författare)
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Ag-catalyzed InAs nanowires grown on transferable graphite flakes
- 2016
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Ingår i: Nanotechnology. - : IOP Publishing. - 1361-6528 .- 0957-4484. ; 27:36
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Tidskriftsartikel (refereegranskat)abstract
- Semiconducting nanowires grown by quasi-van-der-Waals epitaxy on graphite flakes are a new class of hybrid materials that hold promise for scalable nanostructured devices within opto-electronics. Here we report on high aspect ratio and stacking fault free Ag-seeded InAs nanowires grown on exfoliated graphite flakes by molecular beam epitaxy. Ag catalyzes the InAs nanowire growth selectively on the graphite flakes and not on the underlying InAs substrates. This allows for easy transfer of the flexible graphite flakes with as-grown nanowire ensembles to arbitrary substrates by a micro-needle manipulator. Besides the possibilities for fabricating novel nanostructure device designs, we show how this method is used to study the parasitic growth and bicrystal match between the graphite flake and the nanowires by transmission electron microscopy.
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| 14. |
- Razmadze, D., et al.
(författare)
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Supercurrent reversal in ferromagnetic hybrid nanowire Josephson junctions
- 2023
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Ingår i: Physical Review B. - 2469-9950. ; 107:8
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Tidskriftsartikel (refereegranskat)abstract
- We report supercurrent transport measurements in hybrid Josephson junctions comprising semiconducting InAs nanowires with epitaxial ferromagnetic insulator EuS and superconducting Al coatings. The wires display a hysteretic superconducting window close to the coercivity, away from zero external magnetic field. Using a multi-interferometer setup, we measure the current-phase relation of multiple magnetic junctions and find an abrupt switch between π and 0 phases within the superconducting window. We attribute the 0-π transition to the discrete flipping of the EuS domains and provide a qualitative theory showing that a sizable exchange field can polarize the junction and lead to the supercurrent reversal. Both 0 and π phases can be realized at zero external field by demagnetizing the wire.
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| 15. |
- Razmadze, D., et al.
(författare)
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Supercurrent transport through 1e -periodic full-shell Coulomb islands
- 2024
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Ingår i: Physical Review B. - 2469-9950. ; 109:4
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Tidskriftsartikel (refereegranskat)abstract
- We experimentally investigate supercurrent through Coulomb islands, where island and leads are fabricated from semiconducting nanowires with fully surrounding superconducting shells. Applying flux along the wire yields a series of destructive Little-Parks lobes with reentrant supercurrent. We find Coulomb blockade with 2e peak spacing in the zeroth lobe and 1e average spacing, with regions of significant even-odd modulation, in the first lobe. Evolution of Coulomb-peak amplitude through the first lobe is consistent with a theoretical model of supercurrent carried predominantly by zero-energy states in the leads and the island.
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| 16. |
- Vaitiekenas, S., et al.
(författare)
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Evidence for spin-polarized bound states in semiconductor–superconductor–ferromagnetic-insulator islands
- 2022
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Ingår i: Physical Review B. - 2469-9950. ; 105
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Tidskriftsartikel (refereegranskat)abstract
- We report Coulomb blockade transport studies of semiconducting InAs nanowires grown with epitaxial superconducting Al and ferromagnetic insulator EuS on overlapping facets. Comparing experiment to a theoretical model, we associate cotunneling features in even-odd bias spectra with spin-polarized Andreev levels. Results are consistent with zero-field spin splitting exceeding the induced superconducting gap. Energies of subgap states are tunable on either side of zero via electrostatic gates.
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| 17. |
- Zeng, Lunjie, 1983, et al.
(författare)
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Correlation between Electrical Transport and Nanoscale Strain in InAs/In0.6Ga0.4As Core-Shell Nanowires
- 2018
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 18:8, s. 4949-4956
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Tidskriftsartikel (refereegranskat)abstract
- Free-standing semiconductor nanowires constitute an ideal material system for the direct manipulation of electrical and optical properties by strain engineering. In this study, we present a direct quantitative correlation between electrical conductivity and nanoscale lattice strain of individual InAs nanowires passivated with a thin epitaxial In0.6Ga0.4As shell. With an in situ electron microscopy electromechanical testing technique, we show that the piezoresistive response of the nanowires is greatly enhanced compared to bulk InAs, and that uniaxial elastic strain leads to increased conductivity, which can be explained by a strain-induced reduction in the band gap. In addition, we observe inhomogeneity in strain distribution, which could have a reverse effect on the conductivity by increasing the scattering of charge carriers. These results provide a direct correlation of nanoscale mechanical strain and electrical transport properties in free-standing nanostructures.
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| 18. |
- Zeng, Lunjie, 1983, et al.
(författare)
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The Effect of Bending Deformation on Charge Transport and Electron Effective Mass of p-doped GaAs Nanowires
- 2019
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Ingår i: Physica Status Solidi - Rapid Research Letetrs. - : Wiley. - 1862-6254 .- 1862-6270. ; 13:8
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The crystal and electronic structure of semiconductor nanowire systems have shown sensitive response to mechanical strain, enabling novel and improved electrical, and optoelectrical properties in nanowires by strain engineering. Here, the response of current–voltage (I–V) characteristics and band structure of individual p-doped GaAs nanowires to bending deformation is studied by in situ electron microscopy combined with theoretical simulations. The I–V characteristics of the nanowire change from linear to nonlinear as bending deformation is applied. The nonlinearity increases with strain. As opposed to the case of uniaxial strain in GaAs, the bending deformation does not give rise to a change in the band gap of GaAs nanowire according to in situ electron energy loss spectroscopy (EELS) measurements. Instead, the response to bending deformation can be explained by strain induced valence band shift, which results in an energy barrier for charge carrier transport along the nanowire. Moreover, the electron effective mass decreases as the strain changes from compressive to tensile across the GaAs nanowire in the bent region. Results from this study shed light on the complex interplay between lattice strain, band structure, and charge transport in semiconductor nanomaterials.
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