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Moutanabbir O, Assali S, Attiaoui A, Daligou G, Daoust P, Vecchio PD, Koelling S, Luo L, Rotaru N. Nuclear Spin-Depleted, Isotopically Enriched 70 Ge/ 28 Si 70 Ge Quantum Wells. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024; 36:e2305703. [PMID: 38009242 DOI: 10.1002/adma.202305703] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2023] [Revised: 11/15/2023] [Indexed: 11/28/2023]
Abstract
The p-symmetry of the hole wavefunction is associated with a weaker hyperfine interaction, which makes hole spin qubits attractive candidates to implement quantum processors. However, recent studies demonstrate that hole qubits are still very sensitive to nuclear spin bath, thus highlighting the need for nuclear spin-free germanium (Ge) qubits to suppress this decoherence channel. Herein, this work demonstrates the epitaxial growth of 73 Ge- and 29 Si-depleted, isotopically enriched 70 Ge/silicon-germanium (SiGe) quantum wells. The growth is achieved by reduced pressure chemical vapor deposition using isotopically purified monogermane 70 GeH4 and monosilane 28 SiH4 with an isotopic purity higher than 99.9% and 99.99%, respectively. The quantum wells consist of a series of 70 Ge/SiGe heterostructures grown on Si wafers. The isotopic purity is investigated using atom probe tomography (APT) following an analytical procedure addressing the discrepancies caused by the overlap of isotope peaks in mass spectra. The nuclear spin background is found to be sensitive to the growth conditions with the lowest concentration of 73 Ge and 29 Si is below 0.01% in the Ge well and SiGe barriers. The measured average distance between nuclear spins reaches 3-4 nm in 70 Ge/28 Si70 Ge, which is an order of magnitude larger than in natural Ge/SiGe heterostructures. The spread of the hole wavefunction and the residual nuclear spin background in APT voluminals comparable to the size of realistic quantum dots are also discussed.
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Affiliation(s)
- Oussama Moutanabbir
- Department of Engineering Physics, École Polytechnique de Montréal, C.P. 6079, Succ. Centre-Ville, Montréal, Québec, H3C 3A7, Canada
| | - Simone Assali
- Department of Engineering Physics, École Polytechnique de Montréal, C.P. 6079, Succ. Centre-Ville, Montréal, Québec, H3C 3A7, Canada
| | - Anis Attiaoui
- Department of Engineering Physics, École Polytechnique de Montréal, C.P. 6079, Succ. Centre-Ville, Montréal, Québec, H3C 3A7, Canada
| | - Gérard Daligou
- Department of Engineering Physics, École Polytechnique de Montréal, C.P. 6079, Succ. Centre-Ville, Montréal, Québec, H3C 3A7, Canada
| | - Patrick Daoust
- Department of Engineering Physics, École Polytechnique de Montréal, C.P. 6079, Succ. Centre-Ville, Montréal, Québec, H3C 3A7, Canada
| | - Patrick Del Vecchio
- Department of Engineering Physics, École Polytechnique de Montréal, C.P. 6079, Succ. Centre-Ville, Montréal, Québec, H3C 3A7, Canada
| | - Sebastian Koelling
- Department of Engineering Physics, École Polytechnique de Montréal, C.P. 6079, Succ. Centre-Ville, Montréal, Québec, H3C 3A7, Canada
| | - Lu Luo
- Department of Engineering Physics, École Polytechnique de Montréal, C.P. 6079, Succ. Centre-Ville, Montréal, Québec, H3C 3A7, Canada
| | - Nicolas Rotaru
- Department of Engineering Physics, École Polytechnique de Montréal, C.P. 6079, Succ. Centre-Ville, Montréal, Québec, H3C 3A7, Canada
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Abstract
Li diffusion is investigated in Li2O-deficient, (110) oriented LiNbO3single crystals in the temperature range between 523 and 673 K by secondary ion mass spectrometry. A thin layer of ion-beam sputtered isotope enriched6LiNbO3was used as a tracer source, which allows one to study pure isotope interdiffusion. The diffusivities coincide with those of (001) oriented single crystals and follow the Arrhenius law with an activation enthalpy of 1.33 eV. The results prove the existence of a three-dimensional diffusion mechanism.
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Rahn J, Hüger E, Dörrer L, Ruprecht B, Heitjans P, Schmidt H. Self-Diffusion of Lithium in Amorphous Lithium Niobate Layers. Z PHYS CHEM 2012. [DOI: 10.1524/zpch.2012.0214] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Abstract
We investigated lithium self-diffusion in amorphous lithium niobate layers between 298 and 423 K. For the experiments, amorphous 6LiNbO3/ 7LiNbO3 isotope hetero-structures were deposited by ion beam sputtering and analysed after diffusion annealing by secondary ion mass spectrometry (SIMS). This arrangement allows one to study pure isotope interdiffusion. The results show that the diffusivities obey the Arrhenius law with an activation enthalpy of 0.7 eV, which is considerably lower than the activation enthalpy found for LiNbO3 single crystals in literature. Consequently, the Li diffusivities are higher by at least eight orders of magnitude in the amorphous samples in the temperature range studied.
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Affiliation(s)
| | - Erwin Hüger
- Technische Universität Clausthal, Institut für Metallurgie, Clausthal-Zellerfeld, Deutschland
| | - Lars Dörrer
- Technische Universität Clausthal, Institut für Metallurgie, Clausthal-Zellerfeld, Deutschland
| | - Benjamin Ruprecht
- Leibniz Universität Hannover, Institut f. Physikalische Chemie und Elektrochemie, Hannover, Deutschland
| | - Paul Heitjans
- Universität Hannover, Institut f. Physikalische Chemie und Elektrochemie, Hannover, Deutschland
| | - Harald Schmidt
- Leibniz Universität Hannover, ZFM-Zentrum f.Festkörperchemie u. Neue Materialien, Hannover, Deutschland
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Rahn J, Hüger E, Dörrer L, Ruprecht B, Heitjans P, Schmidt H. Li self-diffusion in lithium niobate single crystals at low temperatures. Phys Chem Chem Phys 2012; 14:2427-33. [DOI: 10.1039/c2cp23548j] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Schmidt H, Gupta M, Bruns M. Nitrogen diffusion in amorphous silicon nitride isotope multilayers probed by neutron reflectometry. PHYSICAL REVIEW LETTERS 2006; 96:055901. [PMID: 16486954 DOI: 10.1103/physrevlett.96.055901] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2005] [Indexed: 05/06/2023]
Abstract
Amorphous silicon nitride is a model system for a covalently bound amorphous solid with a low atomic mobility where reasonable values of self-diffusivities are still lacking. We used neutron reflectometry on isotope enriched Si3 14N4/Si3 15N4 multilayers to determine nitrogen self-diffusivities ranging from 10(-24) to 10(-21) m2/s between 950 and 1250 degrees C. Time dependent diffusivities observed at 1150 degrees C indicate the presence of structural relaxation. For long annealing times (relaxed state) the diffusivities follow an Arrhenius law with an activation enthalpy of (3.6 +/- 0.4) eV. The results are indicative of a direct diffusion mechanism without the involvement of thermal point defects.
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Affiliation(s)
- H Schmidt
- AG Thermochemie und Mikrokinetik, Fakultät für Natur-und Materialwissenschaften, TU Clausthal, D-38678 Clausthal-Zellerfeld, Germany
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Strohm A, Voss T, Frank W, Laitinen P, Räisänen J. Self-diffusion of71Ge and31Si in Si–Ge alloys. ACTA ACUST UNITED AC 2002. [DOI: 10.3139/146.020737] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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8
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HALLER EE. Isotopically Controlled Semiconductors. J NUCL SCI TECHNOL 2002. [DOI: 10.1080/18811248.2002.9715208] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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Bracht H, Nicols SP, Walukiewicz W, Silveira JP, Briones F, Haller EE. Large disparity between gallium and antimony self-diffusion in gallium antimonide. Nature 2000; 408:69-72. [PMID: 11081507 DOI: 10.1038/35040526] [Citation(s) in RCA: 88] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The most fundamental mass transport process in solids is self-diffusion. The motion of host-lattice ('self-') atoms in solids is mediated by point defects such as vacancies or interstitial atoms, whose formation and migration enthalpies determine the kinetics of this thermally activated process. Self-diffusion studies also contribute to the understanding of the diffusion of impurities, and a quantitative understanding of self- and foreign-atom diffusion in semiconductors is central to the development of advanced electronic devices. In the past few years, self-diffusion studies have been performed successfully with isotopically controlled semiconductor heterostructures of germanium, silicon, gallium arsenide and gallium phosphide. Self-diffusion studies with isotopically controlled GaAs and GaP have been restricted to Ga self-diffusion, as only Ga has two stable isotopes, 69Ga and 71Ga. Here we report self-diffusion studies with an isotopically controlled multilayer structure of crystalline GaSb. Two stable isotopes exist for both Ga and Sb, allowing the simultaneous study of diffusion on both sublattices. Our experiments show that near the melting temperature, Ga diffuses more rapidly than Sb by over three orders of magnitude. This surprisingly large difference in atomic mobility requires a physical explanation going beyond standard diffusion models. Combining our data for Ga and Sb diffusion with related results for foreign-atom diffusion in GaSb (refs 8, 9), we conclude that the unusually slow Sb diffusion in GaSb is a consequence of reactions between defects on the Ga and Sb sublattices, which suppress the defects that are required for Sb diffusion.
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Affiliation(s)
- H Bracht
- University of California and Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
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Kazimirov A, Zegenhagen J, Cardona M. Isotopic mass and lattice constant: X-ray standing wave measurements. Science 1998; 282:930-2. [PMID: 9794760 DOI: 10.1126/science.282.5390.930] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The molecular volume of crystals depends on their isotopic masses. This influence originates from the zero-point motion and the resulting small differences in lattice constants. This effect was measured with high precision by using an x-ray standing wave. The standing wave is generated during Bragg reflection and thus is in phase with the planes of the substrate crystal, which is covered with a homoepitaxial film that has a different isotopic composition than the substrate. The positions of the surface planes of the film with respect to the substrate planes are revealed by the photoelectrons excited by the maxima of the standing wave. For germanium-76 on natural germanium(111), a difference in lattice constant of -1.1 x 10(-5) and -2.5 x 10(-5) at 300 and 54 kelvin, respectively, was found. The results are in good agreement with theoretical predictions.
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Affiliation(s)
- A Kazimirov
- Max-Planck-Institut fur Festkorperforschung Heisenbergstrasse 1, D-70569 Stuttgart, Germany
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Wang L, Hsu L, Haller EE, Erickson JW, Fischer A, Eberl K, Cardona M. Ga self-diffusion in GaAs isotope heterostructures. PHYSICAL REVIEW LETTERS 1996; 76:2342-2345. [PMID: 10060673 DOI: 10.1103/physrevlett.76.2342] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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