| 1. |
- Gómez, Víctor J., et al.
(författare)
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Wafer-scale nanofabrication of sub-100 nm arrays by deep-UV displacement Talbot lithography
- 2020
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 31:29
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Tidskriftsartikel (refereegranskat)abstract
- In this manuscript, we demonstrate the potential of replacing the standard bottom anti-reflective coating (BARC) with a polymethylglutarimide (PMGI) layer for wafer-scale nanofabrication by means of deep-UV displacement talbot lithography (DTL). PMGI is functioning as a developable non-UV sensitive bottom anti-reflective coating (DBARC). After introducing the fabrication process using a standard BARC-based coating and the novel PMGI-based one, the DTL nanopatterning capabilities for both coatings are compared by means of the fabrication of etched nanoholes in a dielectric layer and metal nanodots made by lift-off. Improvement of DTL capabilities are attributed to a reduction of process complexity by avoiding the use of O2 plasma etching of the BARC layer. We show the capacity of this approach to produce nanoholes or nanodots with diameters ranging from 95 to 200 nm at a wafer-scale using only one mask and a proper exposing dose. The minimum diameter of the nanoholes is reduced from 118 to 95 nm when using the PMGI-based coating instead of the BARC-based one. The possibilities opened by the PMGI-based coating are illustrated by the successful fabrication of an array of nanoholes with sub-100 nm diameter for GaAs nanowire growth on a 2″ GaAs wafer, a 2″ nanoimprint lithography (NIL) master stamp, and an array of Au nanodots made by lift-off on a 4″ silica wafer. Therefore, DTL possess the potential for wafer-scale manufacturing of nano-engineered materials.
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| 2. |
- Scandi, Matteo, et al.
(författare)
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Minimally Dissipative Information Erasure in a Quantum Dot via Thermodynamic Length
- 2022
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Ingår i: Physical Review Letters. - 0031-9007. ; 129:27
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Tidskriftsartikel (refereegranskat)abstract
- In this Letter, we explore the use of thermodynamic length to improve the performance of experimental protocols. In particular, we implement Landauer erasure on a driven electron level in a semiconductor quantum dot, and compare the standard protocol in which the energy is increased linearly in time with the one coming from geometric optimization. The latter is obtained by choosing a suitable metric structure, whose geodesics correspond to optimal finite-time thermodynamic protocols in the slow driving regime. We show experimentally that geodesic drivings minimize dissipation for slow protocols, with a bigger improvement as one approaches perfect erasure. Moreover, the geometric approach also leads to smaller dissipation even when the time of the protocol becomes comparable with the equilibration timescale of the system, i.e., away from the slow driving regime. Our results also illustrate, in a single-electron device, a fundamental principle of thermodynamic geometry: optimal finite-time thermodynamic protocols are those with constant dissipation rate along the process.
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| 3. |
- Dorsch, Sven, et al.
(författare)
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Gate control, g factors, and spin-orbit energy of p -type GaSb nanowire quantum dot devices
- 2021
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Ingår i: Physical Review B. - 2469-9950. ; 103:24
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Tidskriftsartikel (refereegranskat)abstract
- Proposals for quantum information applications are frequently based on the coherent manipulation of spins confined to quantum dots. For these applications, p-type III-V material systems promise a reduction of the hyperfine interaction while maintaining large g factors and strong spin-orbit interaction. In this Letter, we study bottom-gated device architectures to realize single and serial multiquantum dot systems in Schottky-contacted p-type GaSb nanowires. We find that the effect of potentials applied to gate electrodes on the nanowire is highly localized to the immediate vicinity of the gate electrode only, which prevents the formation of double quantum dots with commonly used device architectures. We further study the transport properties of a single quantum dot induced by bottom gating and find large gate-voltage dependent variations of the g∗ factors up to 8.1±0.2 as well as spin-orbit energies between 110 and 230 μeV.
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| 4. |
- Khan, Waqar, et al.
(författare)
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Efficient and continuous microwave photoconversion in hybrid cavity-semiconductor nanowire double quantum dot diodes
- 2021
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- Converting incoming photons to electrical current is the key operation principle of optical photodetectors and it enables a host of emerging quantum information technologies. The leading approach for continuous and efficient detection in the optical domain builds on semiconductor photodiodes. However, there is a paucity of efficient and continuous photon detectors in the microwave regime, because photon energies are four to five orders of magnitude lower therein and conventional photodiodes do not have that sensitivity. Here we tackle this gap and demonstrate how microwave photons can be efficiently and continuously converted to electrical current in a high-quality, semiconducting nanowire double quantum dot resonantly coupled to a cavity. In particular, in our photodiode device, an absorbed photon gives rise to a single electron tunneling through the double dot, with a conversion efficiency reaching 6%.
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| 5. |
- Jash, Asmita, et al.
(författare)
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Excitonic Dynamics at the Type-II Polytype Interface of InP Platelets
- 2023
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Ingår i: ACS Photonics. - 2330-4022. ; 10:9, s. 3143-3148
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Tidskriftsartikel (refereegranskat)abstract
- Indirect excitons are the focus of intense research due to the opportunity of studying degenerate quantum gases and liquids in an excitonic system. To realize such systems, it is highly advantageous to have as little scattering as possible. A polytype type-II interface is formed between wurtzite and zincblende InP due to the band alignment. Electrons gather on the zincblende and holes on the wurtzite side of the interface. Therefore, electrons and holes that are spatially separated by the interface form indirect excitons with aligned dipoles. This polytype type-II interface is perfectly flat, which limits scattering. Here we report that repulsive interaction between the indirect excitons is the driving force behind the long-range transport of indirect excitons along the interface at high exciton densities. This is indicative of less scattering than in conventional type-II heterostructures. The spatial separation of the charge carriers across the interface leads to a low recombination rate of the indirect excitons since the overlap of the electron-hole wavefunction at the interface is small. Emission from the long-lived indirect excitons can be detected even after 40 μs. Our studies have been performed by using spatially and temporally resolved photoluminescence at the low temperature.
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| 6. |
- Lai, Kwan To, et al.
(författare)
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Fano resonance between Stokes and anti-Stokes Brillouin scattering
- 2021
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Ingår i: Physical Review Research. - 2643-1564. ; 3
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Tidskriftsartikel (refereegranskat)abstract
- In recent years, the manipulation of Fano resonances in the time domain has unlocked deep insights into a broad spectrum of systems' coherent dynamics. Here, inelastic scattering of light with coherent acoustic phonons is harnessed to achieve complex Fano resonances. The sudden change of phonon momentum during reflection leads to a transition from anti-Stokes to Stokes light scattering, producing two different resonances that interfere in the measurement process. We highlight the conditions necessary to achieve such interference, revealing an underlying symmetry between photons and phonons, and verify the theory experimentally. Then, we demonstrate the possibility to characterize energy and coherence losses at rough interfaces, thus providing a mechanism for nondestructive testing of interface quality. Our results describe numerous unexplained observations in ultrafast acoustics and can be generalized to the scattering of light with any waves.
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| 7. |
- Mante, Pierre-Adrien, et al.
(författare)
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Ultrafast Optical Generation of Coherent Bright and Dark Surface Phonon Polaritons in Nanowires
- 2020
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Ingår i: ACS Photonics. - : American Chemical Society (ACS). - 2330-4022. ; 7:8, s. 1923-1931
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Tidskriftsartikel (refereegranskat)abstract
- The subwavelength confinement and enhanced electric field created by plasmons allow precise sensing and enhanced light–matter interaction. However, the high frequency and short lifetime of plasmons limit the full potential of this technology. It is crucial to find substitutes and to study their dynamics. Here, we propose an experimental approach allowing the time-domain study of surface phonon polaritons. We first build a theoretical framework for the interaction of ultrashort pulses of light with polar materials. We then perform femtosecond pump–probe experiments and demonstrate the generation and time-resolved detection of surface phonon polaritons. By comparing experiments and simulations, we show the presence of both bright and dark modes with quality factors up to 115. We then investigate mode-dependent decay and energy transfer to the environment. Our results offer a platform for the experimental exploration of the dynamics of surface phonon polaritons and of the role of coherence in energy transfer.
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| 8. |
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| 9. |
- Anttu, Nicklas, et al.
(författare)
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Crystal Phase-Dependent Nanophotonic Resonances in InAs Nanowire Arrays
- 2014
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 14:10, s. 5650-5655
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Tidskriftsartikel (refereegranskat)abstract
- Nanostructures have many material, electronic, and optical properties that are not found in bulk systems and that are relevant for technological applications. For example, nanowires realized from III-V semiconductors can be grown into wurtzite crystal structure. This crystal structure does not naturally exist in bulk where these materials form the zinc-blende counterpart. Being able to concomitantly grow these nanowires in the zinc-blende and/or wurtzite crystal structure prlovides an important degree of control for the design and optimization of optoelectronic applications based on these semiconductor nanostructures. However, the refractive indices of this new crystallographic phase have so far not been elucidated. This shortcoming makes it impossible to predict and utilize he full potential of these new nanostructured materials for optoelectronics applications a careful design and optimization of optical resonances by tuning the nanostrucuted geometry is needed to achieve optimal performance. Here, we report and analyze striking differeences in the optical response of nanophotonic resonances in wurtzite and zinc-blend InAs nanowire arrays. Specifically, through reflectance measurements we find that the resonance can be tuned down to lambda approximate to 380 nm in wurtzite nanowires by decreasing the nanowire diameter. In stark contrast, a similar tuning to below approximate to 500 nm is not possible in the zinc-blende nanowires. Furthermore, we find that the wurtzite nanowires can absorb twice as strongly as the zinc-blende nanowires. We attribute these strikingly large differences in resonant behavior to large differences between the refractive indices of the two crystallographic phases realized in these nanostructures. We anticipate our finding to be relevant for other III-B materials as well as for all material systems that manifest polytypism. Taken together, our results demonstrate crystal phase engineering as a potentially new design dimension for optoelectronics applications.
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