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Emneord:
LENS,
SMN
Publikasjoner
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Åsland, Anna Cecilie; Bakkelund, Johannes; Thingstad, Even; Røst, Håkon; Cooil, Simon Phillip & Hu, Jinbang
[Vis alle 11 forfattere av denne artikkelen]
(2023).
One-dimensional spin-polarized surface states: A comparison of Bi(112) with other vicinal bismuth surfaces.
Physical review B (PRB).
ISSN 2469-9950.
108(20).
doi:
10.1103/PhysRevB.108.205403.
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Vicinal surfaces of bismuth are unique test beds for investigating one-dimensional (1D) spin-polarized surface states that may one day be used in spintronic devices. In this paper, such states have been observed for the (112) surface when measured using angle- and spin-resolved photoemission spectroscopy, and also when calculated using a tight-binding model and with density functional theory. The surface states appear as elongated Dirac-cones which are 1D and almost dispersionless in the ky direction, but disperse with energy in the orthogonal kx direction to form two ×-like features centered at the ky line through Γ. Unlike many materials considered for spintronic applications, their 1D nature suggests that conductivity and spin-transport properties are highly dependent on direction. The spin polarization of the surface states is mainly in plane and parallel to the 1D states, but there are signs of a tilted out-of-plane spin-vector component for one of the features. The Bi(112) surface states resemble those found for other vicinal surfaces of bismuth, strongly indicating that their existence and general properties are robust properties of vicinal bismuth surfaces. Furthermore, differences in the details of the states, particularly related to their spin polarization, suggest that the electronic band structure may be engineered simply by precise cutting and polishing of the crystal.
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Røst, Håkon; Cooil, Simon Phillip; Åsland, Anna Cecilie; Hu, Jinbang; Ali, Ayaz & Taniguchi, Takashi
[Vis alle 12 forfattere av denne artikkelen]
(2023).
Phonon-Mediated Quasiparticle Lifetime Renormalizations in Few-Layer Hexagonal Boron Nitride.
Nano Letters.
ISSN 1530-6984.
23(16),
s. 7539–7545.
doi:
10.1021/acs.nanolett.3c02086.
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Understanding the collective behavior of the quasiparticles in solid-state systems underpins the field of non-volatile electronics, including the opportunity to control many-body effects for well-desired physical phenomena and their applications. Hexagonal boron nitride (hBN) is a wide energy bandgap semiconductor, showing immense potential as a platform for low-dimensional device heterostructures. It is an inert dielectric used for gated devices, having a negligible orbital hybridization when placed in contact with other systems. Despite its inertness, we discover a large electron mass enhancement in few-layer hBN affecting the lifetime of the pi-band states. We show that the renormalization is phonon-mediated and consistent with both single- and multiple-phonon scattering events. Our findings thus unveil a so-far unknown many-body state in a wide-bandgap insulator, having important implications for devices using hBN as one of their building blocks.
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Bahramy, Mohammed Saeed; Clark, Oliver J.; Yang, Bohm Jung; Feng, Jiagui; Bawden, Lewis & Riley, Jonathon M.
[Vis alle 26 forfattere av denne artikkelen]
(2018).
Ubiquitous formation of bulk Dirac cones and topological surface states from a single orbital manifold in transition-metal dichalcogenides.
Nature Materials.
ISSN 1476-1122.
17(1),
s. 21–27.
doi:
10.1038/NMAT5031.
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Jorge, Marina; Polyakov, Stanislav; Cooil, Simon Phillip; Schenk, Alex Kevin; Edmonds, Mark & Thomsen, Lars
[Vis alle 8 forfattere av denne artikkelen]
(2017).
Robust p-type doping of copper oxide using nitrogen implantation.
Materials Research Express.
ISSN 2053-1591.
4(7).
doi:
10.1088/2053-1591/aa7613.
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We demonstrate robust p-type doping of Cu2O using low/medium energy ion implantation. Samples are made by controlled oxidation of annealed Cu metal foils, which results in Cu2O with levels of doping close to intrinsic. Samples are then implanted with nitrogen ions using a kinetic energy in the few keV range. Using this method, we are able to produce very high levels of doping, as evidenced by a 350 meV shift in the Fermi level towards the VB maximum.
The robustness of the nitrogen implanted samples are tested by exposing them to atmospheric contaminants, and elevated temperatures. The samples are found to survive an increase in temperature of many hundreds of degrees. The robustness of the samples, combined with the fact that the materials used are safe, abundant and non-toxic and that the methods used for the growth of Cu2O and N+ implantation are simple and cheap to implement industrially, underlines the potential of Cu2O:N for affordable intermediate band photovoltaics.
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Cooil, Simon Phillip; Mørtsell, Eva Anne; Mazzola, Federico; Jorge, Marina; Wenner, Sigurd & Edmonds, M T
[Vis alle 15 forfattere av denne artikkelen]
(2016).
Thermal migration of alloying agents in aluminium.
Materials Research Express.
ISSN 2053-1591.
3(11).
doi:
10.1088/2053-1591/3/11/116501.
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The in situ thermal migration of alloying agents in an Al–Mg–Si–Li alloy is studied using surface sensitive photo-electron and electron diffraction/imaging techniques. Starting with the preparation of an almost oxide free surface (oxide thickness = 0.1 nm), the relative abundance of alloying agents (Mg, Li and Si) at the surface are recorded at various stages of thermal annealing, from room temperature to melting (which is observed at 550 ◦C). Prior to annealing, the surface abundances are below the detection limit Lt1%, in agreement with their bulk concentrations of 0.423% Si, 0.322% Mg and 0.101% Li (atomic %). At elevated temperatures, all three alloying agents appear at drastically increased concentrations (13.3% Si, 19.7% Mg and 45.3% Li), but decrease again with further elevation of the annealing temperature or after melting. The temperature at which the migration occurs is species dependent, with Li migration occurring at significantly higher temperatures than Si and Mg. The mechanism of migration also appears to be species dependent with Li migration occurring all over the surface but Mg migration being restricted to grain boundaries.
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Mazzola, Federico; Nematollahi, Mohammadreza; Li, Zheshen; Cooil, Simon, Phillip; Yang, Xiaodong & Reenaas, Turid Worren
[Vis alle 7 forfattere av denne artikkelen]
(2015).
Resonant photoemission spectroscopy for intermediate band materials.
Applied Physics Letters.
ISSN 0003-6951.
107:192102(19).
doi:
10.1063/1.4935536.
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Resonant photoemission spectroscopy is used to study the intermediate-band material Cr dopedZnS. Using resonant photoemission, we show that the intermediate-band can be characterized, revealing the filling and specific orbital character of the states contributing to the resonant photoemission signal. We demonstrate that resonant photoemission spectroscopy is a powerful approach for understanding the origin of intermediate bands in dopedZnS. The methodology can be widely extended to a large variety of materials, providing useful information towards engineering of high efficiency intermediate band solar cells and of other optoelectronic devices.
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Cooil, Simon, Phillip; Wells, Justin; Hu, Di; Niu, Yuran; Zakharov, Alexei & Bianchi, Marco
[Vis alle 7 forfattere av denne artikkelen]
(2015).
Controlling the growth of epitaxial graphene on metalized diamond (111) surface.
Applied Physics Letters.
ISSN 0003-6951.
107:181603(18).
doi:
10.1063/1.4935073.
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The 2-dimensional transformation of the diamond (111) surface to graphene has been demonstrated using ultrathin Fe films that catalytically reduce the reaction temperature needed for the conversion of sp3 to sp2 carbon. An epitaxial system is formed, which involves the re-crystallization of carbon at the Fe/vacuum interface and that enables the controlled growth of monolayer and multilayer graphene films. In order to study the initial stages of single and multilayer graphene growth, real time monitoring of the system was preformed within a photoemission and low energy electron microscope. It was found that the initial graphene growth occurred at temperatures as low as 500 °C, whilst increasing the temperature to 560 °C was required to produce multi-layer graphene of high structural quality. Angle resolved photoelectron spectroscopy was used to study the electronic properties of the grown material, where a graphene-like energy momentum dispersion was observed. The Dirac point for the first layer is located at 2.5 eV below the Fermi level, indicating an n-type doping of the graphene due to substrate interactions, while that of the second graphene layer lies close to the Fermi level.
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Bianchi, M; Song, F; Cooil, Simon Phillip; Monsen, Åsmund Fløystad; Wahlström, Erik & Miwa, JA
[Vis alle 14 forfattere av denne artikkelen]
(2015).
One-dimensional spin texture of Bi(441): Quantum spin Hall properties without a topological insulator.
Physical Review B. Condensed Matter and Materials Physics.
ISSN 1098-0121.
91(16).
doi:
10.1103/PhysRevB.91.165307.
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Beckwith, Kai Sandvold; Cooil, Simon Phillip; Wells, Justin & Sikorski, Pawel
(2015).
Tunable high aspect ratio polymer nanostructures for cell interfaces.
Nanoscale.
ISSN 2040-3364.
7(18),
s. 8438–8450.
doi:
10.1039/c5nr00674k.
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Jensen, Ingvild Julie Thue; Thøgersen, Annett; Cooil, Simon Phillip; Wells, Justin William; Prytz, Øystein & Von Wenckstern, Holger
(2023).
Bandgap and band offset engineering in κ-Ga2O3-based thin films (Invited talk)).
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Olsen, Vegard Skiftestad; Øversjøen, Vetle; Frodason, Ymir Kalmann; Cooil, Simon; Lee, In-Hwan & Vines, Lasse
[Vis alle 7 forfattere av denne artikkelen]
(2021).
Electrical control in ZnSnN2 by tailoring intrinsic and extrinsic defects.
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Chellappan, Rajesh Kumar; Cooil, Simon Phillip; Dahl, Oystein & Wells, Justin
(2019).
Insitu study of graphene patterning on SiC.
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Chellappan, Rajesh Kumar; Cooil, Simon Phillip; Dahl, Oystein & Wells, Justin
(2018).
Transition metal mediated growth of epitaxial graphene on SiC and intercalation of SiOx for radiation sensing application.
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Schenk, Alex Kevin; Pakpour-Tabrizi, Alex; Mazzola, Federico; Holt, Ann Julie; Nyborg, Thomas & Cooil, Simon Phillip
[Vis alle 13 forfattere av denne artikkelen]
(2018).
Using ARPES as a tool for exploring quantisation in delta-doped silicon and diamond.
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Vinje, Jakob; Beckwith, Kai Sandvold; Cooil, Simon Phillip; Wells, Justin & Sikorski, Pawel
(2017).
Nano-structured surfaces and controlled surface chemistry for cell studies.
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Vinje, Jakob; Beckwith, Kai Sandvold; Cooil, Simon Phillip; Wells, Justin & Sikorski, Pawel
(2017).
Nano-structuring and controlled surface chemistry for cell-studies and biomedical applications.
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Publisert
10. sep. 2020 13:12
- Sist endret
31. aug. 2022 14:35