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3 results on '"type doping"'

1. Experimental Demonstration of a Magnetically Induced Warping Transition in a Topological Insulator Mediated by Rare-Earth Surface Dopants [Dataset]

Author

Valbuena, Miguel A. [miguelangel.valbuena@imdea.org], Muñiz, Beatriz, Ferreiros, Yago, Pantaleón, Pierre A., Dai, Ji, Tallarida, Massimo, Figueroa, Adriana I., Marinova, Vera, García-Díez, Kevin, Mugarza, Aitor, Valenzuela, Sergio O., Miranda, Rodolfo, Camarero, Julio, Guinea, F., Silva-Guillén, José Ángel, Valbuena, Miguel A., Valbuena, Miguel A. [miguelangel.valbuena@imdea.org], Muñiz, Beatriz, Ferreiros, Yago, Pantaleón, Pierre A., Dai, Ji, Tallarida, Massimo, Figueroa, Adriana I., Marinova, Vera, García-Díez, Kevin, Mugarza, Aitor, Valenzuela, Sergio O., Miranda, Rodolfo, Camarero, Julio, Guinea, F., Silva-Guillén, José Ángel, and Valbuena, Miguel A.

Abstract

Magnetic topological insulators constitute a novel class of materials whose topological surface states (TSSs) coexist with long-range ferromagnetic order, eventually breaking time-reversal symmetry. The subsequent bandgap opening is predicted to co-occur with a distortion of the TSS warped shape from hexagonal to trigonal. We demonstrate such a transition by means of angle-resolved photoemission spectroscopy on the magnetically rare-earth (Er and Dy) surface-doped topological insulator Bi2Se2Te. Signatures of the gap opening are also observed. Moreover, increasing the dopant coverage results in a tunable p-type doping of the TSS, thereby allowing for a gradual tuning of the Fermi level toward the magnetically induced bandgap. A theoretical model where a magnetic Zeeman out-of-plane term is introduced in the Hamiltonian governing the TSS rationalizes these experimental results. Our findings offer new strategies to control magnetic interactions with TSSs and open up viable routes for the realization of the quantum anomalous Hall effect.

Published
2023

2. Amphipathic Side Chain of a Conjugated Polymer Optimizes Dopant Location toward Efficient N-Type Organic Thermoelectrics

Author

Thomas D. Anthopoulos, Chen Yao, Ryan C. Chiechi, Derya Baran, Hinderikus G. O. Potgieser, Remco W. A. Havenith, Diego Rosas Villalva, Giuseppe Portale, Jingjin Dong, Selim Sami, L. Jan Anton Koster, Gang Ye, Jian Liu, Marten Koopmans, Simone Fabiano, Xinkai Qiu, Hengda Sun, Xuwen Yang, Mohamad Insan Nugraha, Photophysics and OptoElectronics, Molecular Energy Materials, Theoretical Chemistry, and Macromolecular Chemistry & New Polymeric Materials

Subjects
Materials science, organic thermoelectrics, Library science, 02 engineering and technology, 010402 general chemistry, 01 natural sciences, MECHANISMS, Polymerkemi, conjugated polymers, General Materials Science, dopant location, N‐ type doping, Seebeck coefficient, solution processing, Mechanical Engineering, type doping, Polymer Chemistry, 021001 nanoscience & nanotechnology, 0104 chemical sciences, Chemistry, Scholarship, N&#8208, Mechanics of Materials, Research council, N-type doping, 0210 nano-technology
Abstract

There is no molecular strategy for selectively increasing the Seebeck coefficient without reducing the electrical conductivity for organic thermoelectrics. Here, it is reported that the use of amphipathic side chains in an n-type donor-acceptor copolymer can selectively increase the Seebeck coefficient and thus increase the power factor by a factor of approximate to 5. The amphipathic side chain contains an alkyl chain segment as a spacer between the polymer backbone and an ethylene glycol type chain segment. The use of this alkyl spacer does not only reduce the energetic disorder in the conjugated polymer film but can also properly control the dopant sites away from the backbone, which minimizes the adverse influence of counterions. As confirmed by kinetic Monte Carlo simulations with the host-dopant distance as the only variable, a reduced Coulombic interaction resulting from a larger host-dopant distance contributes to a higher Seebeck coefficient for a given electrical conductivity. Finally, an optimized power factor of 18 mu W m(-1) K-2 is achieved in the doped polymer film. This work provides a facile molecular strategy for selectively improving the Seebeck coefficient and opens up a new route for optimizing the dopant location toward realizing better n-type polymeric thermoelectrics. Funding Agencies|STW/NWOTechnologiestichting STWNetherlands Organization for Scientific Research (NWO) [VIDI 13476]; China Scholarship CouncilChina Scholarship Council; Center for Information Technology of the University of Groningen; Swedish Research CouncilSwedish Research Council [2016-03979]; Olle Engkvists Stiftelse [204-0256]; Advanced Functional Materials center at LiU [2009 00971]; King Abdullah University of Science and Technology (KAUST) Office of Sponsored Research (OSR) [OSR-CRG2018-3737]; NWO Exact and Natural Sciences [2020/ENW/00852342]

Published
2020

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