The Experts below are selected from a list of 54126 Experts worldwide ranked by ideXlab platform
Hongqi Xu - One of the best experts on this subject based on the ideXlab platform.
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coulomb blockade from the shell of an inp inas core shell nanowire with a triangular cross section
Applied Physics Letters, 2019Co-Authors: D J O Goransson, Magnus Heurlin, B Dalelkhan, Simon Abay, Maria E Messing, V F Maisi, Magnus T Borgstrom, Hongqi XuAbstract:We report on growth of InP-InAs core-shell nanowires and demonstration of the formation of single quantum structures, which show the Coulomb blockade effect, over entire lengths of the nanowires. The core-shell nanowires are grown by a selective area growth technique via metal-organic vapor phase epitaxy. The as-grown core-shell nanowires are found to be of wurtzite crystals. The InP cores have a hexagonal cross section, while the InAs shells are grown preferentially on specific { 1 1 ¯ 00} facets, leading to the formation of the core-shell nanowires with an overall triangular cross section. The grown core-shell nanowires are transferred onto a Si/SiO2 substrate and then contacted by several narrow metal electrodes. Low-temperature transport measurements show the Coulomb-blockade effect. We analyze the measured gate capacitance and single electron Charging Energy of the devices and demonstrate that a quantum structure which shows the Coulomb blockade effect of a many-electron quantum dot is formed over the full length of a single core-shell nanowire and consists of the entire InAs shell in the nanowire.We report on growth of InP-InAs core-shell nanowires and demonstration of the formation of single quantum structures, which show the Coulomb blockade effect, over entire lengths of the nanowires. The core-shell nanowires are grown by a selective area growth technique via metal-organic vapor phase epitaxy. The as-grown core-shell nanowires are found to be of wurtzite crystals. The InP cores have a hexagonal cross section, while the InAs shells are grown preferentially on specific { 1 1 ¯ 00} facets, leading to the formation of the core-shell nanowires with an overall triangular cross section. The grown core-shell nanowires are transferred onto a Si/SiO2 substrate and then contacted by several narrow metal electrodes. Low-temperature transport measurements show the Coulomb-blockade effect. We analyze the measured gate capacitance and single electron Charging Energy of the devices and demonstrate that a quantum structure which shows the Coulomb blockade effect of a many-electron quantum dot is formed ove...
Alois Lugstein - One of the best experts on this subject based on the ideXlab platform.
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coulomb blockade in monolithic and monocrystalline al ge al nanowire heterostructures
Applied Physics Letters, 2020Co-Authors: Masiar Sistani, Jovian Delaforce, Karthik Srikanth Bharadwaj, Mai Hoang Luong, Nacenta J Mendivil, Nicolas Roch, Den M Hertog, R B G Kramer, O Buisson, Alois LugsteinAbstract:We report the realization of Ge single-hole transistors based on Al-Ge-Al nanowire (NW) heterostructures. The formation of these axial structures is enabled by a thermally induced exchange reaction at 350 °C between the initial Ge NW and Al contact pads, leading to a monolithic and monocrystalline Al-Ge-Al NW. The 25 nm-diameter Ge segment is a quasi-1D hole channel. Its length is defined by two abrupt Al-Ge Schottky tunnel barriers. At low temperatures, the device shows a single hole transistor signature with well pronounced Coulomb oscillations. The barrier strength between the Ge segment and the Al leads can be tuned as a function of the gate voltage VG. It leads to a zero conductance at VG= 0 V to a few quantum conductance at VG= –15 V. When the gate voltage increases from –5 V to –3 V, the Charging Energy is extracted and it varies from 0.39 meV to 2.42 meV.We report the realization of Ge single-hole transistors based on Al-Ge-Al nanowire (NW) heterostructures. The formation of these axial structures is enabled by a thermally induced exchange reaction at 350 °C between the initial Ge NW and Al contact pads, leading to a monolithic and monocrystalline Al-Ge-Al NW. The 25 nm-diameter Ge segment is a quasi-1D hole channel. Its length is defined by two abrupt Al-Ge Schottky tunnel barriers. At low temperatures, the device shows a single hole transistor signature with well pronounced Coulomb oscillations. The barrier strength between the Ge segment and the Al leads can be tuned as a function of the gate voltage VG. It leads to a zero conductance at VG= 0 V to a few quantum conductance at VG= –15 V. When the gate voltage increases from –5 V to –3 V, the Charging Energy is extracted and it varies from 0.39 meV to 2.42 meV.
Masiar Sistani - One of the best experts on this subject based on the ideXlab platform.
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coulomb blockade in monolithic and monocrystalline al ge al nanowire heterostructures
Applied Physics Letters, 2020Co-Authors: Masiar Sistani, Jovian Delaforce, Karthik Srikanth Bharadwaj, Mai Hoang Luong, Nacenta J Mendivil, Nicolas Roch, Den M Hertog, R B G Kramer, O Buisson, Alois LugsteinAbstract:We report the realization of Ge single-hole transistors based on Al-Ge-Al nanowire (NW) heterostructures. The formation of these axial structures is enabled by a thermally induced exchange reaction at 350 °C between the initial Ge NW and Al contact pads, leading to a monolithic and monocrystalline Al-Ge-Al NW. The 25 nm-diameter Ge segment is a quasi-1D hole channel. Its length is defined by two abrupt Al-Ge Schottky tunnel barriers. At low temperatures, the device shows a single hole transistor signature with well pronounced Coulomb oscillations. The barrier strength between the Ge segment and the Al leads can be tuned as a function of the gate voltage VG. It leads to a zero conductance at VG= 0 V to a few quantum conductance at VG= –15 V. When the gate voltage increases from –5 V to –3 V, the Charging Energy is extracted and it varies from 0.39 meV to 2.42 meV.We report the realization of Ge single-hole transistors based on Al-Ge-Al nanowire (NW) heterostructures. The formation of these axial structures is enabled by a thermally induced exchange reaction at 350 °C between the initial Ge NW and Al contact pads, leading to a monolithic and monocrystalline Al-Ge-Al NW. The 25 nm-diameter Ge segment is a quasi-1D hole channel. Its length is defined by two abrupt Al-Ge Schottky tunnel barriers. At low temperatures, the device shows a single hole transistor signature with well pronounced Coulomb oscillations. The barrier strength between the Ge segment and the Al leads can be tuned as a function of the gate voltage VG. It leads to a zero conductance at VG= 0 V to a few quantum conductance at VG= –15 V. When the gate voltage increases from –5 V to –3 V, the Charging Energy is extracted and it varies from 0.39 meV to 2.42 meV.
Attila Geresdi - One of the best experts on this subject based on the ideXlab platform.
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broadband microwave spectroscopy of semiconductor nanowire based cooper pair transistors
Physical Review B, 2019Co-Authors: Alex Proutski, Dominique Laroche, Bas Van T Hooft, Peter Krogstrup, Jesper Nygard, L P Kouwenhoven, Attila GeresdiAbstract:The Cooper-pair transistor (CPT), a small superconducting island enclosed between two Josephson weak links, is the atomic building block of various superconducting quantum circuits. Utilizing gate-tunable semiconductor channels as weak links, the Energy scale associated with the Josephson tunneling can be changed with respect to the Charging Energy of the island, tuning the extent of its charge fluctuations. Here, we directly demonstrate this control by mapping the Energy level structure of a CPT made of an indium arsenide nanowire with a superconducting aluminum shell. We extract the device parameters based on the exhaustive modeling of the quantum dynamics of the phase-biased nanowire CPT and directly measure the even-odd parity occupation ratio as a function of the device temperature, relevant for superconducting and prospective topological qubits.
L P Kouwenhoven - One of the best experts on this subject based on the ideXlab platform.
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broadband microwave spectroscopy of semiconductor nanowire based cooper pair transistors
Physical Review B, 2019Co-Authors: Alex Proutski, Dominique Laroche, Bas Van T Hooft, Peter Krogstrup, Jesper Nygard, L P Kouwenhoven, Attila GeresdiAbstract:The Cooper-pair transistor (CPT), a small superconducting island enclosed between two Josephson weak links, is the atomic building block of various superconducting quantum circuits. Utilizing gate-tunable semiconductor channels as weak links, the Energy scale associated with the Josephson tunneling can be changed with respect to the Charging Energy of the island, tuning the extent of its charge fluctuations. Here, we directly demonstrate this control by mapping the Energy level structure of a CPT made of an indium arsenide nanowire with a superconducting aluminum shell. We extract the device parameters based on the exhaustive modeling of the quantum dynamics of the phase-biased nanowire CPT and directly measure the even-odd parity occupation ratio as a function of the device temperature, relevant for superconducting and prospective topological qubits.
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andreev reflection versus coulomb blockade in hybrid semiconductor nanowire devices
Nano Letters, 2008Co-Authors: Silvano De Franceschi, Erik P A M Bakkers, L P KouwenhovenAbstract:Semiconductor nanowires provide promising low-dimensional systems for the study of quantum transport phenomena in combination with superconductivity. Here we investigate the competition between the Coulomb blockade effect, Andreev reflection, and quantum interference, in InAs and InP nanowires connected to aluminum-based superconducting electrodes. We compare three limiting cases depending on the tunnel coupling strength and the characteristic Coulomb interaction Energy. For weak coupling and large Charging energies, negative differential conductance is observed as a direct consequence of the BCS density of states in the leads. For intermediate coupling and Charging Energy smaller than the superconducting gap, the current-voltage characteristic is dominated by Andreev reflection and Coulomb blockade produces an effect only near zero bias. For almost ideal contact transparencies and negligible Charging energies, we observe universal conductance fluctuations whose amplitude is enhanced because of Andreev reflection at the contacts.