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40 items found (0 items not approved), displaying 1 to 10.[First/Prev] 1, 2, 3, 4 [Next/Last]

Instruments / Technical Area	Publication Details	Published
I09-Surface and Interface Structural Analysis	Tuning band alignment at a semiconductor-crystalline oxide heterojunction via electrostatic modulation of the interfacial dipole M. Chrysler , J. Gabel , T.-L. Lee , A. N. Penn , B. E. Matthews , D. M. Kepaptsoglou , Q. M. Ramasse , J. R. Paudel , R. K. Sah , J. D. Grassi , Z. Zhu , A. X. Gray , J. M. Lebeau , S. R. Spurgeon , S. A. Chambers , P. V. Sushko , J. H. Ngai Physical Review Materials 5 DOI: 10.1103/PhysRevMaterials.5.104603 Diamond Proposal Number(s): [25582, 26487] Show Abstract ▼ Abstract: We demonstrate that the interfacial dipole associated with bonding across the SrTi O 3 / Si heterojunction can be tuned through space charge, thereby enabling the band alignment to be altered via doping. Oxygen impurities in Si act as donors that create space charge by transferring electrons across the interface into SrTi O 3 . The space charge induces an electric field that modifies the interfacial dipole, thereby tuning the band alignment from type II to III. The transferred charge, accompanying built-in electric fields, and change in band alignment are manifested in electrical transport and hard x-ray photoelectron spectroscopy measurements. Ab initio models reveal the interplay between polarization and band offsets. We find that band offsets can be tuned by modulating the density of space charge across the interface. Modulating the interface dipole to enable electrostatic altering of band alignment opens additional pathways to realize functional behavior in semiconducting hybrid heterojunctions.	Oct 2021
I09-Surface and Interface Structural Analysis	Identification of hidden orbital contributions in the La0.65Sr0.35MnO3 valence band F. Offi , K. Yamauchi , S. Picozzi , V. Lollobrigida , A. Verna , C. Schlueter , T.-L. Lee , A. Regoutz , D. J. Payne , A. Petrov , G. Vinai , G. M. Pierantozzi , T. Pincelli , G. Panaccione , F. Borgatti Physical Review Materials 5 DOI: 10.1103/PhysRevMaterials.5.104403 Diamond Proposal Number(s): [11322] Show Abstract ▼ Abstract: Hybridization of electronic states and orbital symmetry in transition metal oxides are generally considered key ingredients in the description of both their electronic and magnetic properties. In the prototypical case of La 0.65 Sr 0.35 MnO 3 (LSMO), a landmark system for spintronics applications, a description based solely on Mn 3 d and O 2 p electronic states is reductive. We thus analyzed elemental and orbital distributions in the LSMO valence band through a comparison between density functional theory calculations and experimental photoelectron spectra in a photon energy range from soft to hard x rays. We reveal a number of hidden contributions, arising specifically from La 5 p , Mn 4 s , and O 2 s orbitals, considered negligible in previous analyses; our results demonstrate that all these contributions are significant for a correct description of the valence band of LSMO and of transition metal oxides in general.	Oct 2021
I09-Surface and Interface Structural Analysis	Growth, domain structure, and atomic adsorption sites of hBN on the Ni(111) surface Miriam Raths , Christina Schott , Johannes Knippertz , Markus Franke , You-Ron Lin , Anja Haags , Martin Aeschlimann , Christian Kumpf , Benjamin Stadtmüller Physical Review Materials 5 DOI: 10.1103/PhysRevMaterials.5.094001 Diamond Proposal Number(s): [18787] Show Abstract ▼ Abstract: One of the most important functionalities of the atomically thin insulator hexagonal boron nitride (hBN) is its ability to chemically and electronically decouple functional materials from highly reactive surfaces. It is therefore of utmost importance to uncover its structural properties on surfaces on an atomic and mesoscopic length scale. In this paper, we quantify the relative coverages of structurally different domains of a hBN layer on the Ni(111) surface using low-energy electron microscopy and the normal incidence x-ray standing wave technique. We find that hBN nucleates on defect sites of the Ni(111) surface and predominantly grows in two epitaxial domains that are rotated by 60 ∘ with respect to each other. The two domains reveal identical adsorption heights, indicating a similar chemical interaction strength with the Ni(111) surface. The different azimuthal orientations of these domains originate from different adsorption sites of N and B. We demonstrate that the majority ( ≈ 70 % ) of hBN domains exhibit a ( N , B ) = ( top , fcc ) adsorption site configuration while the minority ( ≈ 30 % ) show a ( N , B ) = ( top , hcp ) configuration. Our study hence underlines the crucial role of the atomic adsorption configuration in the mesoscopic domain structures of in situ fabricated two-dimensional materials on highly reactive surfaces.	Sep 2021
I10-Beamline for Advanced Dichroism	Ferromagnetism in ultrathin surface-free La0.7Sr0.3MnO3 layers in electrostatically defined heterostructures A. Galdi , N. Coppola , C. Sacco , L. Maritato , P. Bencok , P. Steadman , P. Orgiani , C. Aruta Physical Review Materials 5 DOI: 10.1103/PhysRevMaterials.5.084409 Diamond Proposal Number(s): [14915] Show Abstract ▼ Abstract: Electrostatically defined perovskite oxide heterostructures, in which carriers are confined by the modulation of the A-site ion charge, offer new possibilities of tuning the magnetic properties of manganite oxides. We investigate the preferential orientation of ferromagnetic and antiferromagnetic moments in ultrathin La 0.7 Sr 0.3 MnO 3 layers embedded in antiferromagnetic Sr MnO 3 as they undergo a metal-to-insulator transition with decreasing thickness. Our results evince the role of orbital occupation, metallicity, and competition of different magnetic phases, in absence of spurious effects occurring in thin films as a result of symmetry breaking at La 0.7 Sr 0.3 MnO 3 interfaces and of incorporation of oxygen vacancies.	Aug 2021
I09-Surface and Interface Structural Analysis	Controlling the electronic interface properties of AlOx / SrTiO3 heterostructures Berengar Leikert , Judith Gabel , Matthias Schmitt , Martin Stuebinger , Philipp Scheiderer , Louis Veyrat , Tien-Lin Lee , Michael Sing , Ralph Claessen Physical Review Materials 5 DOI: 10.1103/PhysRevMaterials.5.065003 Diamond Proposal Number(s): [15856] Show Abstract ▼ Abstract: Depositing disordered Al on top of Sr Ti O 3 is a cheap and easy way to create a two-dimensional electron system in the Sr Ti O 3 surface layers. To facilitate future device applications, we passivate the heterostructure by a disordered La Al O 3 capping layer to study the electronic properties by complementary x-ray photoemission spectroscopy and transport measurements on the very same samples. We also tune the electronic interface properties by adjusting the oxygen pressure during film growth.	Jun 2021
I11-High Resolution Powder Diffraction	Substitutional tuning of electronic phase separation in CaFe3O5 Ka H. Hong , Elena Solana-Madruga , Branislav Viliam Hakala , Midori Amano Patino , Pascal Manuel , Yuichi Shimakawa , J. Paul Attfield Physical Review Materials 5 DOI: 10.1103/PhysRevMaterials.5.024406 Show Abstract ▼ Abstract: Electronic phase separation into charge-ordered (CO) and charge-averaged (CA) phases in Ca Fe 3 − x M x O 5 samples for dopants M = Mn and Co has been investigated using powder neutron and x-ray diffraction, magnetization, and Mössbauer spectroscopy measurements. Electronic phase separation is observed in lightly doped Ca Fe 3 O 5 samples, where 4 – 10 % Ca is replaced by Mn, Fe, or Co, and the CA ground state is stabilized at higher doping levels. The CO and CA phases are found to emerge below a common magnetic ordering temperature at 300 – 320 K providing strong evidence for a lattice strain-driven mechanism that couples their magnetic transitions.	Feb 2021
NONE-No attached Diamond beamline	Modification of the van der Waals interaction at the Bi2 Te3 and Ge(111) interface Kenji Nawa , Demie Kepaptsoglou , Arsham Ghasemi , Philip Hasnip , Guillermo Bárcena-González , Giuseppe Nicotra , Pedro L. Galindo , Quentin M. Ramasse , Kohji Nakamura , Susannah C. Speller , Balati Kuerbanjiang , Thorsten Hesjedal , Vlado K. Lazarov Physical Review Materials 5 DOI: 10.1103/PhysRevMaterials.5.024203 Show Abstract ▼ Abstract: We present a structural and density-functional theory study of the interface of the quasi-twin-free grown three-dimensional topological insulator Bi 2 Te 3 on Ge(111). Aberration-corrected scanning transmission electron microscopy and electron energy-loss spectroscopy in combination with first-principles calculations show that the weak van der Waals adhesion between the Bi 2 Te 3 quintuple layer and Ge can be overcome by forming an additional Te layer at their interface. The first-principles calculations of the formation energy of the additional Te layer show it to be energetically favorable as a result of the strong hybridization between the Te and Ge.	Feb 2021
I15-Extreme Conditions	Pressure-induced reconstructive phase transition in Cd3 As2 Monika Gamza , Paolo Abrami , Lawrence V. D. Gammond , Jake Ayres , Israel Osmond , Takaki Muramatsu , Robert Armstrong , Hugh Perryman , Dominik Daisenberger , Sitikantha Das , Sven Friedemann Physical Review Materials 5 DOI: 10.1103/PhysRevMaterials.5.024209 Diamond Proposal Number(s): [19319] Show Abstract ▼ Abstract: Cadmium arsenide ( Cd 3 As 2 ) hosts massless Dirac electrons in its ambient-condition tetragonal phase. We report x-ray diffraction and electrical resistivity measurements of Cd 3 As 2 upon cycling pressure beyond the critical pressure of the tetragonal phase and back to ambient conditions. We find that, at room temperature, the transition between the low- and high-pressure phases results in large microstrain and reduced crystallite size, both on rising and falling pressure. This leads to nonreversible electronic properties, including self-doping associated with defects and a reduction of the electron mobility by an order of magnitude due to increased scattering. This paper indicates that the structural transformation is sluggish and shows a sizable hysteresis of over 1 GPa. Therefore, we conclude that the transition is first-order reconstructive, with chemical bonds being broken and rearranged in the high-pressure phase. Using the diffraction measurements, we demonstrate that annealing at ∼ 200 ∘ C greatly improves the crystallinity of the high-pressure phase. We show that its Bragg peaks can be indexed as a primitive orthorhombic lattice with a HP ≈ 8.68 Å , b HP ≈ 17.15 Å , and c HP ≈ 18.58 Å . The diffraction study indicates that, during the structural transformation, a new phase with another primitive orthorhombic structure may also be stabilized by deviatoric stress, providing an additional venue for tuning the unconventional electronic states in Cd 3 As 2 .	Feb 2021
I05-ARPES	Surface photovoltaic effect and electronic structure of β-InSe L. Kang , L. Shen , Y. J. Chen , S. C. Sun , X. Gu , H. J. Zheng , Z. K. Liu , J. X. Wu , H. L. Peng , F. W. Zheng , P. Zhang , L. X. Yang , Y. L. Chen Physical Review Materials 4 DOI: 10.1103/PhysRevMaterials.4.124604 Diamond Proposal Number(s): [23648, 24827] Show Abstract ▼ Abstract: Using high-resolution angle-resolved photoemission spectroscopy, we systematically investigate the electronic structure of β-InSe, a van der Waals semiconductor with a direct band gap. Our measurements show a good agreement with ab initio calculations, which helps reveal the important impact of spin-orbit coupling on the electronic structure of β-InSe. Using surface potassium doping, we tune the chemical potential of the system and observe the unoccupied conduction band. The direct band gap is determined to be about 1.3 eV. Interestingly, we observe a global band shift when the sample is illuminated by a continuous-wave laser at 632.8 nm, which can be understood by an efficient surface photovoltaic effect. The surface photovoltaic can be tuned by in situ surface potassium doping. Our results not only provide important insights into the semiconducting properties of InSe, but also suggest a feasible method to study and engineer the surface photovoltaic effect in InSe-based devices.	Dec 2020
I06-Nanoscience	Interplay between morphology and magnetoelectric coupling in Fe/PMN-PT multiferroic heterostructures studied by microscopy techniques Federico Motti , G. Vinai , Valentina Bonanni , Vincent Polewczyk , Paola Mantegazza , Thomas Forrest , Francesco Maccherozzi , Stefania Benedetti , Christian Rinaldi , Matteo Cantoni , Damiano Cassese , Stefano Prato , Sarnjeet S. Dhesi , Giorgio Rossi , Giancarlo Panaccione , Piero Torelli Physical Review Materials 4 DOI: 10.1103/PhysRevMaterials.4.114418 Diamond Proposal Number(s): [18810] Show Abstract ▼ Abstract: A ferromagnetic (FM) thin film deposited on a substrate of Pb ( Mg 1 / 3 Nb 2 / 3 ) O 3 − PbTiO 3 (PMN-PT) is an appealing heterostructure for the electrical control of magnetism, which would enable nonvolatile memories with ultralow-power consumption. Reversible and electrically controlled morphological changes at the surface of PMN-PT suggest that the magnetoelectric effects are more complex than the commonly used “strain-mediated” description. Here we show that changes in substrate morphology intervene in magnetoelectric coupling as a key parameter interplaying with strain. Magnetic-sensitive microscopy techniques are used to study magnetoelectric coupling in Fe/PMN-PT at different length scales, and compare different substrate cuts. The observed rotation of the magnetic anisotropy is connected to the changes in morphology, and mapped in the crack pattern at the mesoscopic scale. Ferroelectric polarization switching induces a magnetic field-free rotation of the magnetic domains at micrometer scale, with a wide distribution of rotation angles. Our results show that the relationship between the rotation of the magnetic easy axis and the rotation of the in-plane component of the electric polarization is not straightforward, as well as the relationship between ferroelectric domains and crack pattern. The understanding and control of this phenomenon is crucial to develop functional devices based on FM/PMN-PT heterostructures.	Nov 2020

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