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Limaye MV, Chen SC, Lee CY, Chen LY, Singh SB, Shao YC, Wang YF, Hsieh SH, Hsueh HC, Chiou JW, Chen CH, Jang LY, Cheng CL, Pong WF, Hu YF. Understanding of sub-band gap absorption of femtosecond-laser sulfur hyperdoped silicon using synchrotron-based techniques. Sci Rep 2015; 5:11466. [PMID: 26098075 PMCID: PMC4476416 DOI: 10.1038/srep11466] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2014] [Accepted: 05/26/2015] [Indexed: 11/08/2022] Open
Abstract
The correlation between sub-band gap absorption and the chemical states and electronic and atomic structures of S-hyperdoped Si have been extensively studied, using synchrotron-based x-ray photoelectron spectroscopy (XPS), x-ray absorption near-edge spectroscopy (XANES), extended x-ray absorption fine structure (EXAFS), valence-band photoemission spectroscopy (VB-PES) and first-principles calculation. S 2p XPS spectra reveal that the S-hyperdoped Si with the greatest (~87%) sub-band gap absorption contains the highest concentration of S(2-) (monosulfide) species. Annealing S-hyperdoped Si reduces the sub-band gap absorptance and the concentration of S(2-) species, but significantly increases the concentration of larger S clusters [polysulfides (Sn(2-), n > 2)]. The Si K-edge XANES spectra show that S hyperdoping in Si increases (decreased) the occupied (unoccupied) electronic density of states at/above the conduction-band-minimum. VB-PES spectra evidently reveal that the S-dopants not only form an impurity band deep within the band gap, giving rise to the sub-band gap absorption, but also cause the insulator-to-metal transition in S-hyperdoped Si samples. Based on the experimental results and the calculations by density functional theory, the chemical state of the S species and the formation of the S-dopant states in the band gap of Si are critical in determining the sub-band gap absorptance of hyperdoped Si samples.
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Affiliation(s)
- Mukta V. Limaye
- Department of Physics, Tamkang University,
Tamsui
251, Taiwan
- Department of Physics, Indian Institute of Science Education and
Research, Bhopal
462066, India
| | - S. C. Chen
- Department of Physics, Tamkang University,
Tamsui
251, Taiwan
| | - C. Y. Lee
- Department of Physics, Tamkang University,
Tamsui
251, Taiwan
| | - L. Y. Chen
- Department of Physics, Tamkang University,
Tamsui
251, Taiwan
| | - Shashi B. Singh
- Department of Physics, Tamkang University,
Tamsui
251, Taiwan
- Department of Physics, Indian Institute of Science Education and
Research, Bhopal
462066, India
| | - Y. C. Shao
- Department of Physics, Tamkang University,
Tamsui
251, Taiwan
| | - Y. F. Wang
- Department of Physics, Tamkang University,
Tamsui
251, Taiwan
| | - S. H. Hsieh
- Department of Physics, Tamkang University,
Tamsui
251, Taiwan
| | - H. C. Hsueh
- Department of Physics, Tamkang University,
Tamsui
251, Taiwan
| | - J. W. Chiou
- Department of Applied Physics, National University of
Kaohsiung, Kaohsiung
811, Taiwan
| | - C. H. Chen
- National Synchrotron Radiation Research Center,
Hsinchu
300, Taiwan
| | - L. Y. Jang
- National Synchrotron Radiation Research Center,
Hsinchu
300, Taiwan
| | - C. L. Cheng
- Department of Physics, National Dong Hwa University,
Hualien
974, Taiwan
| | - W. F. Pong
- Department of Physics, Tamkang University,
Tamsui
251, Taiwan
| | - Y. F. Hu
- Canadian Light Source Inc., Saskatoon
SK
S7N OX4, Canada
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Michez L, Chen K, Cheynis F, Leroy F, Ranguis A, Jamgotchian H, Hanbücken M, Masson L. Magnetic properties of self-organized Co dimer nanolines on Si/Ag(110). BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2015; 6:777-84. [PMID: 25977848 PMCID: PMC4419577 DOI: 10.3762/bjnano.6.80] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2014] [Accepted: 02/17/2015] [Indexed: 05/30/2023]
Abstract
We demonstrate the kinetically controlled growth of one-dimensional Co nanomagnets with a high lateral order on a nanopatterned Ag(110) surface. First, self-organized Si nanoribbons are formed upon submonolayer condensation of Si on the anisotropic Ag(110) surface. Depending on the growth temperature, individual or regular arrays (with a pitch of 2 nm) of Si nanoribbons can be grown. Next, the Si/Ag(110) system is used as a novel one-dimensional Si template to guide the growth of Co dimer nanolines on top of the Si nanoribbons, taking advantage of the fact that the thermally activated process of Co diffusion into the Si layer is efficiently hindered at 220 K. Magnetic characterization of the Co nanolines using X-ray magnetic circular dichroism reveals that the first atomic Co layer directly adsorbed onto the Si nanoribbons presents a weak magnetic response. However, the second Co layer exhibits an enhanced magnetization, strongly suggesting a ferromagnetic ordering with an in-plane easy axis of magnetization, which is perpendicular to the Co nanolines.
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Affiliation(s)
- Lisa Michez
- Aix Marseille Université, CNRS, CINaM UMR 7325, 13288 Marseille, France
| | - Kai Chen
- Synchrotron SOLEIL, L’Orme des Merisiers, Saint-Aubin – BP 48, 91192 Gif-sur-Yvette Cedex, France
| | - Fabien Cheynis
- Aix Marseille Université, CNRS, CINaM UMR 7325, 13288 Marseille, France
| | - Frédéric Leroy
- Aix Marseille Université, CNRS, CINaM UMR 7325, 13288 Marseille, France
| | - Alain Ranguis
- Aix Marseille Université, CNRS, CINaM UMR 7325, 13288 Marseille, France
| | - Haik Jamgotchian
- Aix Marseille Université, CNRS, CINaM UMR 7325, 13288 Marseille, France
| | - Margrit Hanbücken
- Aix Marseille Université, CNRS, CINaM UMR 7325, 13288 Marseille, France
| | - Laurence Masson
- Aix Marseille Université, CNRS, CINaM UMR 7325, 13288 Marseille, France
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