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Ming F, Snijders PC, Weitering HH. Controlled Switching of Bistable Nanophase Domains on a Silicon Surface. ACS Nano 2023. [PMID: 37306458 DOI: 10.1021/acsnano.3c03517] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Switching the crystalline phase of a material via electrostatic control is a proven strategy for developing memory devices such as memristors that are based on nonvolatile resistance switching phenomena. However, phase switching in atomic-scale systems is often difficult to control and poorly understood. Here, we explore nonvolatile switching of long 2.3 nm wide bistable nanophase domains in a Sn double-layer structure grown on Si(111), using a scanning tunneling microscope. We identified two mechanisms for this phase switching phenomenon. First, the electrical field across the tunnel gap continuously tunes the relative stability of the two phases and favors one over the other depending on the tunneling polarity. The second mechanism involves carrier injection into empty Sn orbitals. The coupling between these relatively long-lived hot electrons and surface phonons induces a lattice instability at sufficiently large tunneling current and provides access to a hidden metastable state of matter. This hidden state is nonvolatile but can be erased by choosing the appropriate tunneling conditions or raising the temperature. Similar mechanisms could possibly be exploited in phase-change memristor and field effect devices.
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Affiliation(s)
- Fangfei Ming
- State Key Laboratory of Optoelectronic Materials and Technologies, School of Electronics and Information Technology and Guangdong Province Key Laboratory of Display Material, Sun Yat-sen University, Guangzhou 510275, China
| | - Paul C Snijders
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Hanno H Weitering
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996, United States
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2
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Wu X, Ming F, Smith TS, Liu G, Ye F, Wang K, Johnston S, Weitering HH. Superconductivity in a Hole-Doped Mott-Insulating Triangular Adatom Layer on a Silicon Surface. Phys Rev Lett 2020; 125:117001. [PMID: 32976011 DOI: 10.1103/physrevlett.125.117001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Accepted: 08/07/2020] [Indexed: 06/11/2023]
Abstract
Adsorption of one-third monolayer of Sn on an atomically clean Si(111) substrate produces a two-dimensional triangular adatom lattice with one unpaired electron per site. This dilute adatom reconstruction is an antiferromagnetic Mott insulator; however, the system can be modulation doped and metallized using heavily doped p-type Si(111) substrates. Here, we show that the hole-doped dilute adatom layer on a degenerately doped p-type Si(111) wafer is superconducting with a critical temperature of 4.7±0.3 K. While a phonon-mediated coupling scenario would be consistent with the observed T_{c}, Mott correlations in the Sn-derived dangling-bond surface state could suppress the s-wave pairing channel. The latter suggests that the superconductivity in this triangular adatom lattice may be unconventional.
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Affiliation(s)
- Xuefeng Wu
- Department of Physics, Southern University of Science and Technology, Shenzhen, Guangdong 518055, China
| | - Fangfei Ming
- State Key Laboratory of Optoelectronic Materials and Technologies, School of Electronics and Information Technology and Guangdong Province Key Laboratory of Display Material and Technology, Sun Yat-sen University, Guangzhou 510275, China
| | - Tyler S Smith
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996, USA
| | - Guowei Liu
- Department of Physics, Southern University of Science and Technology, Shenzhen, Guangdong 518055, China
| | - Fei Ye
- Department of Physics, Southern University of Science and Technology, Shenzhen, Guangdong 518055, China
| | - Kedong Wang
- Department of Physics, Southern University of Science and Technology, Shenzhen, Guangdong 518055, China
| | - Steven Johnston
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996, USA
| | - Hanno H Weitering
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996, USA
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3
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Smith TS, Ming F, Trabada DG, Gonzalez C, Soler-Polo D, Flores F, Ortega J, Weitering HH. Coupled Sublattice Melting and Charge-Order Transition in Two Dimensions. Phys Rev Lett 2020; 124:097602. [PMID: 32202895 DOI: 10.1103/physrevlett.124.097602] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Accepted: 01/28/2020] [Indexed: 06/10/2023]
Abstract
Two-dimensional melting is one of the most fascinating and poorly understood phase transitions in nature. Theoretical investigations often point to a two-step melting scenario involving unbinding of topological defects at two distinct temperatures. Here, we report on a novel melting transition of a charge-ordered K-Sn alloy monolayer on a silicon substrate. Melting starts with short-range positional fluctuations in the K sublattice while maintaining long-range order, followed by longer-range K diffusion over small domains, and ultimately resulting in a molten sublattice. Concomitantly, the charge order of the Sn host lattice collapses in a multistep process with both displacive and order-disorder transition characteristics. Our combined experimental and theoretical analysis provides a rare insight into the atomistic processes of a multistep melting transition of a two-dimensional materials system.
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Affiliation(s)
- T S Smith
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996, USA
| | - F Ming
- State Key Laboratory of Optoelectronic Materials and Technologies, School of Electronics and Information Technology and Guangdong Province Key Laboratory of Display Material, Sun Yat-sen University, Guangzhou 510275, China
| | - D G Trabada
- Departamento de Física Teórica de la Materia Condensada and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, ES-28049 Madrid, Spain
| | - C Gonzalez
- Departamento de Física Teórica de la Materia Condensada and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, ES-28049 Madrid, Spain
| | - D Soler-Polo
- Departamento de Física Teórica de la Materia Condensada and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, ES-28049 Madrid, Spain
| | - F Flores
- Departamento de Física Teórica de la Materia Condensada and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, ES-28049 Madrid, Spain
| | - J Ortega
- Departamento de Física Teórica de la Materia Condensada and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, ES-28049 Madrid, Spain
| | - H H Weitering
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996, USA
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4
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Ming F, Johnston S, Mulugeta D, Smith TS, Vilmercati P, Lee G, Maier TA, Snijders PC, Weitering HH. Realization of a Hole-Doped Mott Insulator on a Triangular Silicon Lattice. Phys Rev Lett 2017; 119:266802. [PMID: 29328725 DOI: 10.1103/physrevlett.119.266802] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2017] [Indexed: 06/07/2023]
Abstract
The physics of doped Mott insulators is at the heart of some of the most exotic physical phenomena in materials research including insulator-metal transitions, colossal magnetoresistance, and high-temperature superconductivity in layered perovskite compounds. Advances in this field would greatly benefit from the availability of new material systems with a similar richness of physical phenomena but with fewer chemical and structural complications in comparison to oxides. Using scanning tunneling microscopy and spectroscopy, we show that such a system can be realized on a silicon platform. The adsorption of one-third monolayer of Sn atoms on a Si(111) surface produces a triangular surface lattice with half filled dangling bond orbitals. Modulation hole doping of these dangling bonds unveils clear hallmarks of Mott physics, such as spectral weight transfer and the formation of quasiparticle states at the Fermi level, well-defined Fermi contour segments, and a sharp singularity in the density of states. These observations are remarkably similar to those made in complex oxide materials, including high-temperature superconductors, but highly extraordinary within the realm of conventional sp-bonded semiconductor materials. It suggests that exotic quantum matter phases can be realized and engineered on silicon-based materials platforms.
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Affiliation(s)
- Fangfei Ming
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996, USA
| | - Steve Johnston
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996, USA
- Joint Institute of Advanced Materials at The University of Tennessee, Knoxville, Tennessee 37996, USA
| | - Daniel Mulugeta
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996, USA
| | - Tyler S Smith
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996, USA
| | - Paolo Vilmercati
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996, USA
- Joint Institute of Advanced Materials at The University of Tennessee, Knoxville, Tennessee 37996, USA
| | - Geunseop Lee
- Department of Physics, Inha University, Inchon 402-751, Korea
| | - Thomas A Maier
- Computational Science and Engineering Division and Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Paul C Snijders
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996, USA
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Hanno H Weitering
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996, USA
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5
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Ming F, Mulugeta D, Tu W, Smith TS, Vilmercati P, Lee G, Huang YT, Diehl RD, Snijders PC, Weitering HH. Hidden phase in a two-dimensional Sn layer stabilized by modulation hole doping. Nat Commun 2017; 8:14721. [PMID: 28266499 PMCID: PMC5343494 DOI: 10.1038/ncomms14721] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2016] [Accepted: 01/26/2017] [Indexed: 01/21/2023] Open
Abstract
Semiconductor surfaces and ultrathin interfaces exhibit an interesting variety of two-dimensional quantum matter phases, such as charge density waves, spin density waves and superconducting condensates. Yet, the electronic properties of these broken symmetry phases are extremely difficult to control due to the inherent difficulty of doping a strictly two-dimensional material without introducing chemical disorder. Here we successfully exploit a modulation doping scheme to uncover, in conjunction with a scanning tunnelling microscope tip-assist, a hidden equilibrium phase in a hole-doped bilayer of Sn on Si(111). This new phase is intrinsically phase separated into insulating domains with polar and nonpolar symmetries. Its formation involves a spontaneous symmetry breaking process that appears to be electronically driven, notwithstanding the lack of metallicity in this system. This modulation doping approach allows access to novel phases of matter, promising new avenues for exploring competing quantum matter phases on a silicon platform. Broken symmetry phases may occur in 2D materials upon doping, yet introducing doping without inducing chemical disorder remains a challenge. Here, the authors use a modulation doping approach that unveils a hidden equilibrium phase involving spontaneous symmetry breaking in a hole-doped Sn bilayer.
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Affiliation(s)
- Fangfei Ming
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996, USA
| | - Daniel Mulugeta
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996, USA
| | - Weisong Tu
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996, USA
| | - Tyler S Smith
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996, USA
| | - Paolo Vilmercati
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996, USA.,Joint Institute for Advanced Materials at The University of Tennessee, Knoxville, Tennessee 37996, USA
| | - Geunseop Lee
- Department of Physics, Inha University, Inchon 402-751, Korea
| | - Ying-Tzu Huang
- Department of Physics, Penn State University, University Park, Pennsylvania 16802, USA
| | - Renee D Diehl
- Department of Physics, Penn State University, University Park, Pennsylvania 16802, USA
| | - Paul C Snijders
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996, USA.,Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Hanno H Weitering
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996, USA.,Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
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6
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Berlijn T, Snijders PC, Delaire O, Zhou HD, Maier TA, Cao HB, Chi SX, Matsuda M, Wang Y, Koehler MR, Kent PRC, Weitering HH. Itinerant Antiferromagnetism in RuO_{2}. Phys Rev Lett 2017; 118:077201. [PMID: 28256891 DOI: 10.1103/physrevlett.118.077201] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Indexed: 06/06/2023]
Abstract
Bulk rutile RuO_{2} has long been considered a Pauli paramagnet. Here we report that RuO_{2} exhibits a hitherto undetected lattice distortion below approximately 900 K. The distortion is accompanied by antiferromagnetic order up to at least 300 K with a small room temperature magnetic moment of approximately 0.05μ_{B} as evidenced by polarized neutron diffraction. Density functional theory plus U (DFT+U) calculations indicate that antiferromagnetism is favored even for small values of the Hubbard U of the order of 1 eV. The antiferromagnetism may be traced to a Fermi surface instability, lifting the band degeneracy imposed by the rutile crystal field. The combination of high Néel temperature and small itinerant moments make RuO_{2} unique among ruthenate compounds and among oxide materials in general.
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Affiliation(s)
- T Berlijn
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
- Computer Science and Mathematics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - P C Snijders
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996, USA
| | - O Delaire
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
- Mechanical Engineering and Materials Science, Duke University, Durham, North Carolina 27708, USA
| | - H-D Zhou
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996, USA
| | - T A Maier
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
- Computer Science and Mathematics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - H-B Cao
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - S-X Chi
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - M Matsuda
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Y Wang
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - M R Koehler
- Department of Materials Science and Engineering, The University of Tennessee, Knoxville, Tennessee 37996, USA
| | - P R C Kent
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
- Computer Science and Mathematics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - H H Weitering
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996, USA
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7
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Zhang H, Ming F, Kim HJ, Zhu H, Zhang Q, Weitering HH, Xiao X, Zeng C, Cho JH, Zhang Z. Stabilization and manipulation of electronically phase-separated ground states in defective indium atom wires on silicon. Phys Rev Lett 2014; 113:196802. [PMID: 25415916 DOI: 10.1103/physrevlett.113.196802] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2014] [Indexed: 06/04/2023]
Abstract
Exploration and manipulation of electronic states in low-dimensional systems are of great importance in the fundamental and practical aspects of nanomaterial and nanotechnology. Here, we demonstrate that the incorporation of vacancy defects into monatomic indium wires on n-type Si(111) can stabilize electronically phase-separated ground states where the insulating 8×2 and metallic 4×1 phases coexist. Furthermore, the areal ratio of the two phases in the phase-separated states can be tuned reversibly by electric field or charge doping, and such tunabilities can be quantitatively captured by first principles-based modeling and simulations. The present results extend the realm of electronic phase separation from strongly correlated d-electron materials typically in bulk form to weakly interacting sp-electron systems in reduced dimensionality.
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Affiliation(s)
- Hui Zhang
- Hefei National Laboratory for Physical Sciences at the Microscale (HFNL) and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Fangfei Ming
- Department of Physics, The Chinese University of Hong Kong, Shatin, New Territory, Hong Kong, China
| | - Hyun-Jung Kim
- Department of Physics, Hanyang University, 17 Haengdang-Dong, SeongDong-Ku, Seoul 133-791, Korea
| | - Hongbin Zhu
- Hefei National Laboratory for Physical Sciences at the Microscale (HFNL) and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Qiang Zhang
- Hefei National Laboratory for Physical Sciences at the Microscale (HFNL) and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Hanno H Weitering
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996, USA and Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Xudong Xiao
- Department of Physics, The Chinese University of Hong Kong, Shatin, New Territory, Hong Kong, China and Shenzhen Institute of Advanced Technology, Chinese Academy of Science, Shenzhen 518055, China
| | - Changgan Zeng
- Hefei National Laboratory for Physical Sciences at the Microscale (HFNL) and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, China and International Center for Quantum Design of Functional Materials (ICQD), HFNL, University of Science and Technology of China, Hefei, Anhui 230026, China and Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Jun-Hyung Cho
- Department of Physics, Hanyang University, 17 Haengdang-Dong, SeongDong-Ku, Seoul 133-791, Korea
| | - Zhenyu Zhang
- International Center for Quantum Design of Functional Materials (ICQD), HFNL, University of Science and Technology of China, Hefei, Anhui 230026, China and Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
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8
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Affiliation(s)
- Hanno H Weitering
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996, and at Oak Ridge National Laboratory, Tennessee 37831, USA
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9
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Parks Cheney C, Vilmercati P, Martin EW, Chiodi M, Gavioli L, Regmi M, Eres G, Callcott TA, Weitering HH, Mannella N. Origins of electronic band gap reduction in Cr/N codoped TiO2. Phys Rev Lett 2014; 112:036404. [PMID: 24484152 DOI: 10.1103/physrevlett.112.036404] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2013] [Indexed: 06/03/2023]
Abstract
Recent studies indicated that noncompensated cation-anion codoping of wide-band-gap oxide semiconductors such as anatase TiO2 significantly reduces the optical band gap and thus strongly enhances the absorption of visible light [W. Zhu et al., Phys. Rev. Lett. 103, 226401 (2009)]. We used soft x-ray spectroscopy to fully determine the location and nature of the impurity levels responsible for the extraordinarily large (∼1 eV) band gap reduction of noncompensated codoped rutile TiO2. It is shown that Cr/N codoping strongly enhances the substitutional N content, compared to single element doping. The band gap reduction is due to the formation of Cr 3d3 levels in the lower half of the gap while the conduction band minimum is comprised of localized Cr 3d and delocalized N 2p states. Band gap reduction and carrier delocalization are critical elements for efficient light-to-current conversion in oxide semiconductors. These findings thus raise the prospect of using codoped oxide semiconductors with specifically engineered electronic properties in a variety of photovoltaic and photocatalytic applications.
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Affiliation(s)
- C Parks Cheney
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996, USA
| | - P Vilmercati
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996, USA
| | - E W Martin
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996, USA
| | - M Chiodi
- Dipartimento di Matematica e Fisica and Interdisciplinary Laboratories for Advanced Materials Physics, Università Cattolica del Sacro Cuore di Brescia, Via Musei 41, Brescia 25121, Italy
| | - L Gavioli
- Dipartimento di Matematica e Fisica and Interdisciplinary Laboratories for Advanced Materials Physics, Università Cattolica del Sacro Cuore di Brescia, Via Musei 41, Brescia 25121, Italy
| | - M Regmi
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - G Eres
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - T A Callcott
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996, USA
| | - H H Weitering
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996, USA and Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - N Mannella
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996, USA
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10
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Iancu V, Zhang XG, Kim TH, Menard LD, Kent P, Woodson ME, Ramsey JM, Li AP, Weitering HH. Polaronic transport and current blockades in epitaxial silicide nanowires and nanowire arrays. Nano Lett 2013; 13:3684-3689. [PMID: 23902411 PMCID: PMC4010140 DOI: 10.1021/nl401574c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Crystalline micrometer-long YSi2 nanowires with cross sections as small as 1 × 0.5 nm(2) can be grown on the Si(001) surface. Their extreme aspect ratios make electron conduction within these nanowires almost ideally one-dimensional, while their compatibility with the silicon platform suggests application as metallic interconnect in Si-based nanoelectronic devices. Here we combine bottom-up epitaxial wire synthesis in ultrahigh vacuum with top-down miniaturization of the electrical measurement probes to elucidate the electronic conduction mechanism of both individual wires and arrays of nanowires. Temperature-dependent transport through individual nanowires is indicative of thermally assisted tunneling of small polarons between atomic-scale defect centers. In-depth analysis of complex wire networks emphasize significant electronic crosstalk between the nanowires due to the long-range Coulomb fields associated with polaronic charge fluctuations. This work establishes a semiquantitative correlation between the density and distributions of atomic-scale defects and resulting current-voltage characteristics of nanoscale network devices.
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Affiliation(s)
- Violeta Iancu
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, TN 37966, USA
| | - X.-G. Zhang
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
- Computer Science and Mathematics Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Tae-Hwan Kim
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Laurent D. Menard
- Department of Chemistry, University of North Carolina, Chapel Hill, NC 27599, USA
| | - P.R.C. Kent
- Center for Nanophase Materials Sciences and Computer Science and Mathematics Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831
| | - Michael E. Woodson
- Department of Chemistry, University of North Carolina, Chapel Hill, NC 27599, USA
| | - J. Michael Ramsey
- Department of Chemistry, University of North Carolina, Chapel Hill, NC 27599, USA
| | - An-Ping Li
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Hanno H. Weitering
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, TN 37966, USA
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
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11
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Qin S, Kim TH, Zhang Y, Ouyang W, Weitering HH, Shih CK, Baddorf AP, Wu R, Li AP. Correlating electronic transport to atomic structures in self-assembled quantum wires. Nano Lett 2012; 12:938-942. [PMID: 22268695 DOI: 10.1021/nl204003s] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Quantum wires, as a smallest electronic conductor, are expected to be a fundamental component in all quantum architectures. The electronic conductance in quantum wires, however, is often dictated by structural instabilities and electron localization at the atomic scale. Here we report on the evolutions of electronic transport as a function of temperature and interwire coupling as the quantum wires of GdSi(2) are self-assembled on Si(100) wire-by-wire. The correlation between structure, electronic properties, and electronic transport are examined by combining nanotransport measurements, scanning tunneling microscopy, and density functional theory calculations. A metal-insulator transition is revealed in isolated nanowires, while a robust metallic state is obtained in wire bundles at low temperature. The atomic defects lead to electron localizations in isolated nanowire, and interwire coupling stabilizes the structure and promotes the metallic states in wire bundles. This illustrates how the conductance nature of a one-dimensional system can be dramatically modified by the environmental change on the atomic scale.
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Affiliation(s)
- Shengyong Qin
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
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12
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Özer MM, Moon EJ, Eguiluz AG, Weitering HH. Plasmon response of a quantum-confined electron gas probed by core-level photoemission. Phys Rev Lett 2011; 106:197601. [PMID: 21668200 DOI: 10.1103/physrevlett.106.197601] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2010] [Revised: 03/21/2011] [Indexed: 05/30/2023]
Abstract
We demonstrate the existence of quantized "bulk" plasmons in ultrathin magnesium films on Si(111) by analyzing plasmon-loss satellites in core-level photoemission spectra, recorded as a function of the film thickness d. Remarkably, the plasmon energy is shown to vary as 1/d2 all the way down to three atomic layers. The loss spectra are dominated by the n=1 and n=2 normal modes, consistent with the excitation of plasmons involving quantized electronic subbands. With decreasing film thickness, spectral weight is gradually transferred from the plasmon modes to the low-energy single-particle excitations. These results represent striking manifestations of the role of quantum confinement on plasmon resonances in precisely controlled nanostructures.
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Affiliation(s)
- Mustafa M Özer
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
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13
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Jia Y, Wu B, Li C, Einstein TL, Weitering HH, Zhang Z. Strong quantum size effects in Pb(111) thin films mediated by anomalous Friedel oscillations. Phys Rev Lett 2010; 105:066101. [PMID: 20867988 DOI: 10.1103/physrevlett.105.066101] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2010] [Indexed: 05/29/2023]
Abstract
Using first-principles calculations within density functional theory, we study Friedel oscillations (FOs) in the electron density at different metal surfaces and their influence on the lattice relaxation and stability of ultrathin metal films. We show that the FOs at the Pb(111) surface decay as 1/x with the distance x from the surface, different from the conventional 1/x(2) power law at other metal surfaces. The underlying physical reason for this striking difference is tied to the strong nesting of the two different Fermi sheets along the Pb(111) direction. The interference of the strong FOs emanating from the two surfaces of a Pb(111) film, in turn, not only results in superoscillatory interlayer relaxations around the center of the film, but also determines its stability in the quantum regime. As a simple and generic picture, the present findings also explain why quantum size effects are exceptionally robust in Pb(111) films.
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Affiliation(s)
- Yu Jia
- School of Physics and Engineering, Zhengzhou University, Zhengzhou, Henan, 450052, China
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14
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Affiliation(s)
- Hanno H Weitering
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, TN 37996, USA.
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15
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Zhu W, Qiu X, Iancu V, Chen XQ, Pan H, Wang W, Dimitrijevic NM, Rajh T, Meyer HM, Paranthaman MP, Stocks GM, Weitering HH, Gu B, Eres G, Zhang Z. Band gap narrowing of titanium oxide semiconductors by noncompensated anion-cation codoping for enhanced visible-light photoactivity. Phys Rev Lett 2009; 103:226401. [PMID: 20366114 DOI: 10.1103/physrevlett.103.226401] [Citation(s) in RCA: 117] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2009] [Indexed: 05/29/2023]
Abstract
"Noncompensated n-p codoping" is established as an enabling concept for enhancing the visible-light photoactivity of TiO2 by narrowing its band gap. The concept embodies two crucial ingredients: the electrostatic attraction within the n-p dopant pair enhances both the thermodynamic and kinetic solubilities, and the noncompensated nature ensures the creation of tunable intermediate bands that effectively narrow the band gap. The concept is demonstrated using first-principles calculations, and is validated by direct measurements of band gap narrowing using scanning tunneling spectroscopy, dramatically redshifted optical absorbance, and enhanced photoactivity manifested by efficient electron-hole separation in the visible-light region. This concept is broadly applicable to the synthesis of other advanced functional materials that demand optimal dopant control.
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Affiliation(s)
- Wenguang Zhu
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
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16
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Iancu V, Kent PRC, Zeng CG, Weitering HH. Structure of YSi(2) nanowires from scanning tunneling spectroscopy and first principles. Appl Phys Lett 2009; 95:123107. [PMID: 19859579 PMCID: PMC2766400 DOI: 10.1063/1.3236778] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2009] [Accepted: 09/03/2009] [Indexed: 05/28/2023]
Abstract
Exceptionally long and uniform YSi(2) nanowires are formed via self-assembly on Si(001). The in-plane width of the thinnest wires is known to be quantized in odd multiples of the silicon lattice constant. Here, we identify a class of nanowires that violates the "odd multiple" rule. The structure of the thinnest wire in this category is determined by comparing scanning tunneling spectroscopy measurements with the calculated surface density of states of candidate models by means of the Pendry R-factor analysis. The relative stability of the odd and even wire systems is analyzed via first-principles calculations.
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17
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González C, Guo J, Ortega J, Flores F, Weitering HH. Mechanism of the band gap opening across the order-disorder transition of Si(111)(4 x 1)-In. Phys Rev Lett 2009; 102:115501. [PMID: 19392212 DOI: 10.1103/physrevlett.102.115501] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2008] [Indexed: 05/27/2023]
Abstract
The ground state properties of indium atom chains on the Si(111) 8 x 2-In surface and the nature of their insulator-metal (IM) transition near 120 K are under intense dispute. We compare experimental scanning tunneling microscopy (STM) images of the low temperature (LT) 8 x 2 phase with STM image calculations from Density Functional Theory (DFT). Our LT studies clearly indicate the existence of a frozen shear distortion between neighboring atom chains, resulting in the formation of indium hexagons. Tunneling spectra furthermore indicate that the IM transition coincides with the collapse of a approximately 0.3 eV surface-state band gap at the Gamma point of the 4 x 2 Brillouin zone. This implies that the IM transition is driven by a shear phonon, not by Fermi surface nesting.
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Affiliation(s)
- C González
- Departamento de Física Teórica de la Materia Condensada, Universidad Autónoma, 28049 Madrid, Spain
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18
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Zeng C, Kent PRC, Kim TH, Li AP, Weitering HH. Charge-order fluctuations in one-dimensional silicides. Nat Mater 2008; 7:539-542. [PMID: 18552849 PMCID: PMC4135438 DOI: 10.1038/nmat2209] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2008] [Accepted: 05/16/2008] [Indexed: 05/26/2023]
Abstract
Metallic nanowires are of great interest as interconnects in nanoelectronic devices. They also represent important systems for understanding the complexity of electronic interactions and conductivity in one dimension. We have fabricated exceptionally long and uniform YSi(2) nanowires through self-assembly of yttrium atoms on Si(001). The wire widths are quantized in odd multiples of the Si substrate lattice constant. The thinnest wires represent one of the closest realizations of the isolated Peierls chain, exhibiting van Hove type singularities in the one-dimensional density of states and charge-order fluctuations below 150 K. The structure of the wire was determined through a detailed comparison of scanning tunnelling microscopy data and first-principles calculations. Quantized width variations along the thinnest wires produce built-in Schottky junctions, the electronic properties of which are governed by the finite size and temperature scaling of the charge-ordering correlation. This illustrates how a collective phenomenon such as charge ordering might be exploited in nanoelectronic devices.
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Affiliation(s)
- Changgan Zeng
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996-1200, USA
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19
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Zeng C, Zhang Z, van Benthem K, Chisholm MF, Weitering HH. Optimal doping control of magnetic semiconductors via subsurfactant epitaxy. Phys Rev Lett 2008; 100:066101. [PMID: 18352490 DOI: 10.1103/physrevlett.100.066101] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2007] [Revised: 12/04/2007] [Indexed: 05/26/2023]
Abstract
"Subsurfactant epitaxy" is established as a conceptually new approach for introducing manganese as a magnetic dopant into germanium. A kinetic pathway is devised in which the subsurface interstitial sites on Ge(100) are first selectively populated with Mn, while lateral diffusion and clustering on or underneath the surface are effectively suppressed. Subsequent Ge deposition as a capping layer produces a novel surfactantlike phenomenon as the interstitial Mn atoms float towards newly defined subsurface sites at the growth front. Furthermore, the Mn atoms that failed to float upwards are uniformly distributed within the Ge capping layer. The resulting doping levels of order 0.25 at. % would normally be considered too low for ferromagnetic ordering, but the Curie temperature exceeds room temperature by a comfortable margin. Subsurfactant epitaxy thus enables superior dopant control in magnetic semiconductors.
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Affiliation(s)
- Changgan Zeng
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996, USA
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Kim TH, Wang Z, Wendelken JF, Weitering HH, Li W, Li AP. A cryogenic Quadraprobe scanning tunneling microscope system with fabrication capability for nanotransport research. Rev Sci Instrum 2007; 78:123701. [PMID: 18163731 DOI: 10.1063/1.2821610] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
We describe the development and the capabilities of an advanced system for nanoscale electrical transport studies. This system consists of a low temperature four-probe scanning tunneling microscope (STM) and a high-resolution scanning electron microscope coupled to a molecular-beam epitaxy sample preparation chamber. The four STM probes can be manipulated independently with subnanometer precision, enabling atomic resolution STM imaging and four-point electrical transport study of surface electronic systems and nanostructured materials at temperatures down to 10 K. Additionally, an integrated energy analyzer allows for scanning Auger microscopy to probe chemical species of nanostructures. Some testing results are presented.
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Affiliation(s)
- Tae-Hwan Kim
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
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21
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Snijders PC, Moon EJ, González C, Rogge S, Ortega J, Flores F, Weitering HH. Controlled self-organization of atom vacancies in monatomic gallium layers. Phys Rev Lett 2007; 99:116102. [PMID: 17930452 DOI: 10.1103/physrevlett.99.116102] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2007] [Indexed: 05/25/2023]
Abstract
Ga adsorption on the Si(112) surface results in the formation of pseudomorphic Ga atom chains. Compressive strain in these atom chains is relieved via creation of adatom vacancies and their self-organization into meandering vacancy lines. The average spacing between these line defects can be controlled, within limits, by adjusting the chemical potential mu of the Ga adatoms. We derive a lattice model that quantitatively connects density functional theory (DFT) calculations for perfectly ordered structures with the fluctuating disorder seen in experiment and the experimental control parameter mu. This hybrid approach of lattice modeling and DFT can be applied to other examples of line defects in heteroepitaxy.
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Affiliation(s)
- P C Snijders
- Kavli Institute of NanoScience Delft, Delft University of Technology, 2628 CJ Delft, The Netherlands.
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Abstract
Quantum confinement of itinerant electrons in atomically smooth ultrathin lead films produces strong oscillations in the thickness-dependent film energy. By adding extra electrons via bismuth alloying, we showed that both the structural stability and the superconducting properties of such films can be tuned. The phase boundary (upper critical field) between the superconducting vortex state and the normal state indicates an anomalous suppression of superconducting order just below the critical temperature, Tc. This suppression varies systematically with the film thickness and the bismuth content and can be parametrized in terms of a characteristic temperature, Tc* (less than Tc), that is inversely proportional to the scattering mean free path. The results indicate that the isotropic nature of the superconductive pairing in bulk lead-bismuth alloys is altered in the quantum regime.
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Affiliation(s)
- Mustafa M Ozer
- Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996, USA
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Zeng C, Kent PRC, Varela M, Eisenbach M, Stocks GM, Torija M, Shen J, Weitering HH. Epitaxial stabilization of ferromagnetism in the nanophase of FeGe. Phys Rev Lett 2006; 96:127201. [PMID: 16605951 DOI: 10.1103/physrevlett.96.127201] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2005] [Indexed: 05/08/2023]
Abstract
Epitaxial nanocrystals of FeGe have been stabilized on Ge(111). The nanocrystals assume a quasi-one-dimensional shape as they grow exclusively along the <110> direction of the Ge(111) substrate, culminating in a compressed monoclinic modification of FeGe. Whereas monoclinic FeGe is antiferromagnetic in the bulk, the nanowires are surprisingly strong ferromagnets below approximately 200 K with an average magnetic moment of 0.8 microB per Fe atom. Density functional calculations indicate an unusual stabilization mechanism for the observed ferromagnetism: lattice compression destabilizes the antiferromagnetic Peierls-like ground state observed in the bulk while increased p-d hybridization suppresses the magnetic moments and stabilizes ferromagnetism.
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Affiliation(s)
- Changgan Zeng
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996, USA
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Snijders PC, Rogge S, Weitering HH. Competing periodicities in fractionally filled one-dimensional bands. Phys Rev Lett 2006; 96:076801. [PMID: 16606121 DOI: 10.1103/physrevlett.96.076801] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2005] [Indexed: 05/08/2023]
Abstract
We present a variable temperature scanning tunneling microscopy and spectroscopy study of the Si(553)-Au atomic chain reconstruction. This quasi-one-dimensional system undergoes at least two charge density wave (CDW) transitions, which can be attributed to electronic instabilities in the fractionally filled 1D bands of the high-symmetry phase. Upon cooling, Si(553)-Au first undergoes a single-band Peierls distortion, resulting in period doubling along the chains. This Peierls state is ultimately overcome by a competing x3 CDW, which is accompanied by a x2 periodicity in between the chains. These locked-in periodicities indicate small charge transfer between the nearly 1/2-filled and 1/4-filled bands. The presence and the mobility of atomic-scale dislocations in the x3 CDW state indicates the possibility of manipulating phase solitons carrying a (spin, charge) of (1/2, +/- e/3) or (0, +/-2e/3).
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Affiliation(s)
- P C Snijders
- Kavli Institute of NanoScience, Delft University of Technology, 2628 CJ Delft, The Netherlands
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Zeng C, Yao Y, Niu Q, Weitering HH. Linear magnetization dependence of the intrinsic anomalous Hall effect. Phys Rev Lett 2006; 96:037204. [PMID: 16486762 DOI: 10.1103/physrevlett.96.037204] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2005] [Indexed: 05/06/2023]
Abstract
The anomalous Hall effect is investigated experimentally and theoretically for ferromagnetic thin films of Mn5Ge3. We have separated the intrinsic and extrinsic contributions to the experimental anomalous Hall effect and calculated the intrinsic anomalous Hall conductivity from the Berry curvature of the Bloch states using first-principles methods. The intrinsic anomalous Hall conductivity depends linearly on the magnetization, which can be understood from the long-wavelength fluctuations of the spin orientation at finite temperatures. The quantitative agreement between theory and experiment is remarkably good, not only near 0 K but also at finite temperatures, up to about approximately 240 K (0.8TC).
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Affiliation(s)
- Changgan Zeng
- Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996, USA
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González C, Snijders PC, Ortega J, Pérez R, Flores F, Rogge S, Weitering HH. Formation of atom wires on vicinal silicon. Phys Rev Lett 2004; 93:126106. [PMID: 15447286 DOI: 10.1103/physrevlett.93.126106] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2004] [Indexed: 05/24/2023]
Abstract
The feasibility of creating atomic wires on vicinal silicon surfaces via pseudomorphic step-edge decoration has been analyzed for the case of Ga on Si(112). Scanning tunneling microscopy and density functional theory calculations indicate the formation of Ga zigzag chains intersected by quasiperiodic vacancy lines or "misfit dislocations." This structure strikes a balance between the system's drive towards chemical passivation and its need for strain relaxation in the atom chains. Spatially fluctuating disorder, intrinsic to the reconstruction, originates from the two symmetry-degenerate orientations of the zigzag chains on vicinal Si.
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Affiliation(s)
- C González
- Facultad de Ciencias, Departamento de Fisica Teorica de la Materia Condensada, Universidad Autonoma de Madrid, Madrid 28049, Spain
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Zhu W, Weitering HH, Wang EG, Kaxiras E, Zhang Z. Contrasting growth modes of Mn on Ge(100) and Ge(111) surfaces: subsurface segregation versus intermixing. Phys Rev Lett 2004; 93:126102. [PMID: 15447282 DOI: 10.1103/physrevlett.93.126102] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2004] [Indexed: 05/24/2023]
Abstract
Based on first-principles total energy calculations within density functional theory, we show that a low dose of Mn on Ge(100) initiates in a novel subsurface growth mode, characterized by easy access to, and strong preference for, interstitial sites located between the two topmost Ge layers. Strikingly, such a "subsurfactant action" is preserved even during epitaxial growth of additional Ge layers, analogous to the well-known phenomenon of surfactant action. In contrast, along the [111] orientation, Mn can easily diffuse into the bulk via interstitial sites. These results are discussed within the context of dopant control in dilute magnetic semiconductors.
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Affiliation(s)
- Wenguang Zhu
- Condensed Matter Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
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Abstract
Symmetry, dimensionality, and disorder play a pivotal role in critical phenomena. The atomic imaging capabilities of the scanning tunneling microscope were used to directly visualize the interaction between charge density oscillations and lattice defects in a two-dimensional charge density wave (CDW) system. Point defects act as nucleation centers of the CDW, which, as the temperature is lowered, results in the formation of pinned CDW domains that are separated by atomically abrupt charge boundaries. Incomplete freezing of substitutional disorder at low temperature indicates a novel CDW-mediated hopping of pinning centers.
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Affiliation(s)
- HH Weitering
- Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996, USA. Solid State Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA. Department of Physics, Florida International University, University Park, Mia
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Weitering HH, Shi X, Erwin SC. Band dispersions of the pi -bonded-chain reconstruction of Si(111)3 x 1-Li: A critical evaluation of theory and experiment. Phys Rev B Condens Matter 1996; 54:10585-10592. [PMID: 9984854 DOI: 10.1103/physrevb.54.10585] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Carpinelli JM, Weitering HH. Low-temperature reconstruction pathway to the Si(111)( sqrt(3) x sqrt(3) )R30 degrees-Ag interface. Phys Rev B Condens Matter 1996; 53:12651-12654. [PMID: 9982934 DOI: 10.1103/physrevb.53.12651] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Weitering HH, DiNardo NJ, Pérez-Sandoz R, Chen J, Mele EJ. Structural model for the metal-induced Si(111)3 x 1 reconstruction. Phys Rev B Condens Matter 1994; 49:16837-16840. [PMID: 10010858 DOI: 10.1103/physrevb.49.16837] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Weitering HH, Chen J, DiNardo NJ, Plummer EW. Electron correlation, metallization, and Fermi-level pinning at ultrathin K/Si(111) interfaces. Phys Rev B Condens Matter 1993; 48:8119-8135. [PMID: 10007002 DOI: 10.1103/physrevb.48.8119] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Weitering HH, Ettema AR, Hibma T. Surface states and Fermi-level pinning at epitaxial Pb/Si(111) surfaces. Phys Rev B Condens Matter 1992; 45:9126-9135. [PMID: 10000775 DOI: 10.1103/physrevb.45.9126] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Heslinga DR, Weitering HH, Klapwijk TM, Hibma T. Atomic-structure-dependent Schottky barrier at epitaxial Pb/Si(111) interfaces. Phys Rev Lett 1990; 64:1589-1592. [PMID: 10041436 DOI: 10.1103/physrevlett.64.1589] [Citation(s) in RCA: 31] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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