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Zhang Z, Poelsema B, Zandvliet HJ, van Houselt A. Microscopic Study of the Spinodal Decomposition of Supported Eutectic Droplets During Cooling: PtGe/Ge{110}. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2022; 126:11285-11297. [PMID: 35865794 PMCID: PMC9289948 DOI: 10.1021/acs.jpcc.2c01356] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
We embarked on an in situ low-energy electron microscopy, photo-electron emission microscopy, and selected area low-energy electron diffraction study during the cooling of huge eutectic droplets through the critical stages of the eutectic transition. On this journey through uncharted waters, we revealed an expected initial shrinking of the exposed area of the droplet, followed by an unanticipated expansion. We attribute this behavior to an initial fast amorphization of the interface between the droplet and surface, followed by the recrystallization of Ge expelled from the droplet at the interface. As a major surprise, we discovered the emergence of extensive "spaghetti"-like patterns, which are rationalized in terms of parallel Ge ripples oriented along, mainly, [-554] and [-55-4] directions. They emerge during spinodal decomposition when passing the eutectic temperature of the system. Their sides are defined by Ge{111} and Ge{11-1} vicinals covered with Pt-modified (√3 × √3) superstructures. The distance between adjacent ripples is about 18 nm.
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Quantifying work function differences using low-energy electron microscopy: The case of mixed-terminated strontium titanate. Ultramicroscopy 2019; 200:43-49. [PMID: 30822616 DOI: 10.1016/j.ultramic.2019.02.018] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2018] [Accepted: 02/18/2019] [Indexed: 11/24/2022]
Abstract
For many applications, it is important to measure the local work function of a surface with high lateral resolution. Low-energy electron microscopy is regularly employed to this end since it is, in principle, very well suited as it combines high-resolution imaging with high sensitivity to local electrostatic potentials. For surfaces with areas of different work function, however, lateral electrostatic fields inevitably associated with work function discontinuities deflect the low-energy electrons and thereby cause artifacts near these discontinuities. We use ray-tracing simulations to show that these artifacts extend over hundreds of nanometers and cause an overestimation of the true work function difference near the discontinuity by a factor of 1.6 if the standard image analysis methods are used. We demonstrate on a mixed-terminated strontium titanate surface that comparing LEEM data with detailed ray-tracing simulations leads to much a more robust estimate of the work function difference.
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Nataf GF, Grysan P, Guennou M, Kreisel J, Martinotti D, Rountree CL, Mathieu C, Barrett N. Low energy electron imaging of domains and domain walls in magnesium-doped lithium niobate. Sci Rep 2016; 6:33098. [PMID: 27608605 PMCID: PMC5016809 DOI: 10.1038/srep33098] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2016] [Accepted: 08/19/2016] [Indexed: 11/21/2022] Open
Abstract
The understanding of domain structures, specifically domain walls, currently attracts a significant attention in the field of (multi)-ferroic materials. In this article, we analyze contrast formation in full field electron microscopy applied to domains and domain walls in the uniaxial ferroelectric lithium niobate, which presents a large 3.8 eV band gap and for which conductive domain walls have been reported. We show that the transition from Mirror Electron Microscopy (MEM – electrons reflected) to Low Energy Electron Microscopy (LEEM – electrons backscattered) gives rise to a robust contrast between domains with upwards (Pup) and downwards (Pdown) polarization, and provides a measure of the difference in surface potential between the domains. We demonstrate that out-of-focus conditions of imaging produce contrast inversion, due to image distortion induced by charged surfaces, and also carry information on the polarization direction in the domains. Finally, we show that the intensity profile at domain walls provides experimental evidence for a local stray, lateral electric field.
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Affiliation(s)
- G F Nataf
- SPEC, CEA, CNRS, Université Paris-Saclay, CEA Saclay, 91191 Gif-sur-Yvette Cedex, France.,Materials Research and Technology Department, Luxembourg Institute of Science and Technology, 41 rue du Brill, 4422 Belvaux, Luxembourg
| | - P Grysan
- Materials Research and Technology Department, Luxembourg Institute of Science and Technology, 41 rue du Brill, 4422 Belvaux, Luxembourg
| | - M Guennou
- Materials Research and Technology Department, Luxembourg Institute of Science and Technology, 41 rue du Brill, 4422 Belvaux, Luxembourg
| | - J Kreisel
- Materials Research and Technology Department, Luxembourg Institute of Science and Technology, 41 rue du Brill, 4422 Belvaux, Luxembourg.,Physics and Materials Science Research Unit, University of Luxembourg, 41 rue du Brill, 4422 Belvaux, Luxembourg
| | - D Martinotti
- SPEC, CEA, CNRS, Université Paris-Saclay, CEA Saclay, 91191 Gif-sur-Yvette Cedex, France
| | - C L Rountree
- SPEC, CEA, CNRS, Université Paris-Saclay, CEA Saclay, 91191 Gif-sur-Yvette Cedex, France
| | - C Mathieu
- SPEC, CEA, CNRS, Université Paris-Saclay, CEA Saclay, 91191 Gif-sur-Yvette Cedex, France
| | - N Barrett
- SPEC, CEA, CNRS, Université Paris-Saclay, CEA Saclay, 91191 Gif-sur-Yvette Cedex, France
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Hlawacek G, Jankowski M, Wormeester H, van Gastel R, Zandvliet HJW, Poelsema B. Visualization of steps and surface reconstructions in Helium Ion Microscopy with atomic precision. Ultramicroscopy 2016; 162:17-24. [PMID: 26720438 DOI: 10.1016/j.ultramic.2015.11.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Revised: 11/13/2015] [Accepted: 11/17/2015] [Indexed: 11/17/2022]
Abstract
Helium Ion Microscopy is known for its surface sensitivity and high lateral resolution. Here, we present results of a Helium Ion Microscopy based investigation of a surface confined alloy of Ag on Pt(111). Based on a change of the work function of 25meV across the atomically flat terraces we can distinguish Pt rich from Pt poor areas and visualize the single atomic layer high steps between the terraces. Furthermore, dechanneling contrast has been utilized to measure the periodicity of the hcp/fcc pattern formed in the 2-3 layers thick Ag/Pt alloy film. A periodicity of 6.65nm along the ⟨112⟩ surface direction has been measured. In terms of crystallography a hcp domain is obtained through a lateral displacement of a part of the outermost layer by 1/√3 of a nearest neighbor spacing along ⟨112⟩. This periodicity is measured with atomic precision: coincidence between the Ag and the Pt lattices is observed for 23 Ag atoms on 24 Pt atoms. The findings are perfectly in line with results obtained with Low Energy Electron Microscopy and Phase Contrast Atomic Force Microscopy.
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Affiliation(s)
- Gregor Hlawacek
- Physics of Interfaces and Nanomaterials, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands.
| | - Maciej Jankowski
- Physics of Interfaces and Nanomaterials, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands
| | - Herbert Wormeester
- Physics of Interfaces and Nanomaterials, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands
| | - Raoul van Gastel
- Physics of Interfaces and Nanomaterials, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands
| | - Harold J W Zandvliet
- Physics of Interfaces and Nanomaterials, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands
| | - Bene Poelsema
- Physics of Interfaces and Nanomaterials, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands
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Rault JE, Menteş TO, Locatelli A, Barrett N. Reversible switching of in-plane polarized ferroelectric domains in BaTiO3(001) with very low energy electrons. Sci Rep 2014; 4:6792. [PMID: 25354723 PMCID: PMC4213810 DOI: 10.1038/srep06792] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2014] [Accepted: 10/07/2014] [Indexed: 11/09/2022] Open
Abstract
The switchable bipolar ground state is at the heart of research into ferroelectrics for future, low-energy electronics. Polarization switching by an applied field is a complex phenomenon which depends on the initial domain ordering, defect concentration, electrical boundary conditions and charge screening. Injected free charge may also to be used to reversibly switch in-plane polarized domains. We show that the interaction between the initial domain order and the bulk screening provided by very low energy electrons switches the polarization without the collateral radiation damage which occurs when employing a beam of high energy electrons. Polarization switching during charge injection adds a new dimension to the multifunctionality of ferroelectric oxides.
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Affiliation(s)
- J E Rault
- Synchrotron-SOLEIL, BP 48, Saint-Aubin, F-91192 Gif sur Yvette CEDEX, France
| | - T O Menteş
- Elettra-Sincrotrone Trieste S.C.p.A.. Strada Statale 14 - km 163, 5 in AREA Science Park 34149 Basovizza, Trieste, Italy
| | - A Locatelli
- Elettra-Sincrotrone Trieste S.C.p.A.. Strada Statale 14 - km 163, 5 in AREA Science Park 34149 Basovizza, Trieste, Italy
| | - N Barrett
- CEA, DSM/IRAMIS/SPEC, F-91191 Gif-sur-Yvette Cedex, France
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Zhou ZY, Zheng CX, Tang WX, Tersoff J, Jesson DE. Origin of quantum ring formation during droplet epitaxy. PHYSICAL REVIEW LETTERS 2013; 111:036102. [PMID: 23909340 DOI: 10.1103/physrevlett.111.036102] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2013] [Indexed: 05/16/2023]
Abstract
Droplet epitaxy of GaAs is studied in real time using in situ surface electron microscopy. The resulting movies motivate a theoretical model for quantum ring formation which can explain the origin of nanoscale features such as double rings observed under a variety of experimental conditions. Inner rings correspond to GaAs deposition at the droplet edge, while outer rings result from the reaction of Ga and As atoms diffusing along the surface. The observed variety of morphologies primarily reflects relative changes in the outer rings with temperature and As flux.
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Affiliation(s)
- Z Y Zhou
- School of Physics, Monash University, Victoria 3800, Australia
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Schwarz D, van Gastel R, Zandvliet HJW, Poelsema B. Formation and decay of a compressed phase of 4,4′-biphenyldicarboxylic acid on Cu(001). Phys Chem Chem Phys 2013; 15:5007-16. [DOI: 10.1039/c3cp00049d] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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Rault JE, Ren W, Prosandeev S, Lisenkov S, Sando D, Fusil S, Bibes M, Barthélémy A, Bellaiche L, Barrett N. Thickness-dependent polarization of strained BiFeO3 films with constant tetragonality. PHYSICAL REVIEW LETTERS 2012; 109:267601. [PMID: 23368620 DOI: 10.1103/physrevlett.109.267601] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2012] [Indexed: 06/01/2023]
Abstract
We measure the ferroelectric polarization of BiFeO3 films down to 3.6 nm using low energy electron and photoelectron emission microscopy. The measured polarization decays strongly below a critical thickness of 5-7 nm predicted by continuous medium theory whereas the tetragonal distortion does not change. We resolve this apparent contradiction using first-principles-based effective Hamiltonian calculations. In ultrathin films, the energetics of near open circuit electrical boundary conditions, i.e., an unscreened depolarizing field, drive the system through a phase transition from single out-of-plane polarization to nanoscale stripe domains. It gives rise to an average polarization close to zero as measured by the electron microscopy while maintaining the relatively large tetragonal distortion imposed by the nonzero polarization state of each individual domain.
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Affiliation(s)
- J E Rault
- CEA, DSM/IRAMIS/SPCSI, F-91191 Gif-sur-Yvette Cedex, France
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Examples of electrostatic electron optics: The Farrand and Elektros microscopes and electron mirrors. Ultramicroscopy 2012; 119:9-17. [DOI: 10.1016/j.ultramic.2011.11.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2011] [Revised: 10/24/2011] [Accepted: 11/14/2011] [Indexed: 11/17/2022]
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10
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Schwarz D, van Gastel R, Zandvliet HJW, Poelsema B. Size fluctuations of near critical nuclei and Gibbs free energy for nucleation of BDA on Cu(001). PHYSICAL REVIEW LETTERS 2012; 109:016101. [PMID: 23031116 DOI: 10.1103/physrevlett.109.016101] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2012] [Revised: 05/29/2012] [Indexed: 06/01/2023]
Abstract
We present a low-energy electron microscopy study of nucleation and growth of BDA on Cu(001) at low supersaturation. At sufficiently high coverage, a dilute BDA phase coexists with c(8×8) crystallites. The real-time microscopic information allows a direct visualization of near-critical nuclei, determination of the supersaturation and the line tension of the crystallites, and, thus, derivation of the Gibbs free energy for nucleation. The resulting critical nucleus size nicely agrees with the measured value. Nuclei up to 4-6 times larger still decay with finite probability, urging reconsideration of the classic perception of a critical nucleus.
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Affiliation(s)
- Daniel Schwarz
- Physics of Interfaces and Nanomaterials, MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, NL-7500AE Enschede, Netherlands
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Kennedy SM, Hjort M, Mandl B, Marsell E, Zakharov AA, Mikkelsen A, Paganin DM, Jesson DE. Characterizing the geometry of InAs nanowires using mirror electron microscopy. NANOTECHNOLOGY 2012; 23:125703. [PMID: 22397834 DOI: 10.1088/0957-4484/23/12/125703] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Mirror electron microscopy (MEM) imaging of InAs nanowires is a non-destructive electron microscopy technique where the electrons are reflected via an applied electric field before they reach the specimen surface. However strong caustic features are observed that can be non-intuitive and difficult to relate to nanowire geometry and composition. Utilizing caustic imaging theory we can understand and interpret MEM image contrast, relating caustic image features to the properties and parameters of the nanowire. This is applied to obtain quantitative information, including the nanowire width via a through-focus series of MEM images.
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Affiliation(s)
- S M Kennedy
- School of Physics, Monash University, Victoria 3800, Australia
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Kennedy SM, Zheng CX, Tang WX, Paganin DM, Jesson DE. Addendum. Laplacian image contrast in mirror electron microscopy. Proc Math Phys Eng Sci 2011. [DOI: 10.1098/rspa.2011.0204] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
We extend the theory of Laplacian image contrast in mirror electron microscopy (MEM) to the case where the sample is illuminated by a parallel, collimated beam. This popular imaging geometry corresponds to a modern low energy electron microscope equipped with a magnetic objective lens. We show that within the constraints of the relevant approximations; the results for parallel illumination differ only negligibly from diverging MEM specimen illumination conditions.
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Affiliation(s)
- S. M. Kennedy
- School of Physics, Monash University, Victoria 3800, Australia
| | - C. X. Zheng
- School of Physics, Monash University, Victoria 3800, Australia
| | - W. X. Tang
- School of Physics, Monash University, Victoria 3800, Australia
| | - D. M. Paganin
- School of Physics, Monash University, Victoria 3800, Australia
| | - D. E. Jesson
- School of Physics, Monash University, Victoria 3800, Australia
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13
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Caustic imaging of gallium droplets using mirror electron microscopy. Ultramicroscopy 2011; 111:356-63. [DOI: 10.1016/j.ultramic.2011.01.019] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2010] [Revised: 12/22/2010] [Accepted: 01/11/2011] [Indexed: 11/22/2022]
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14
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Tersoff J, Jesson DE, Tang WX. Decomposition controlled by surface morphology during langmuir evaporation of GaAs. PHYSICAL REVIEW LETTERS 2010; 105:035702. [PMID: 20867779 DOI: 10.1103/physrevlett.105.035702] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2010] [Indexed: 05/29/2023]
Abstract
When GaAs is heated in vacuum, it decomposes into Ga and As as it evaporates. Real-time in situ surface electron microscopy reveals striking bursts of "daughter" droplet nucleation and growth when coalescence of large "parent" droplets exposes nonplanar surface regions. We analyze the behavior, predicting a morphology-dependent congruent evaporation temperature. Based on this we propose a new approach for the self-assembly and positioning of quantum structures via droplet epitaxy, which we demonstrate at the proof-of-concept level.
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Affiliation(s)
- J Tersoff
- IBM T. J. Watson Research Center, Yorktown Heights, New York 10598, USA.
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15
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Kennedy SM, Zheng CX, Tang WX, Paganin DM, Jesson DE. Laplacian image contrast in mirror electron microscopy. Proc Math Phys Eng Sci 2010. [DOI: 10.1098/rspa.2010.0093] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
We discuss an intuitive approach to interpreting mirror electron microscopy (MEM) images, whereby image contrast is primarily caused by the Laplacian of small height or potential variations across a sample surface. This variation is blurred slightly to account for the interaction of the electrons with the electrical potential away from the surface. The method is derived from the established geometrical theory of MEM contrast, and whilst it loses quantitative accuracy outside its domain of validity, it retains a simplicity that enables rapid interpretation of MEM images. A strong parallel exists between this method and out of focus contrast in transmission electron microscopy (TEM), which allows a number of extensions to be made, such as including the effects of spherical and chromatic aberration.
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Affiliation(s)
- S. M. Kennedy
- School of Physics, Monash University, Victoria 3800, Australia
| | - C. X. Zheng
- School of Physics, Monash University, Victoria 3800, Australia
| | - W. X. Tang
- School of Physics, Monash University, Victoria 3800, Australia
| | - D. M. Paganin
- School of Physics, Monash University, Victoria 3800, Australia
| | - D. E. Jesson
- School of Physics, Monash University, Victoria 3800, Australia
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NEPIJKO S, SCHÖNHENSE G. Measurement of potential distribution function on object surface by using an electron microscope in the mirror operation mode. J Microsc 2010; 238:90-4. [DOI: 10.1111/j.1365-2818.2009.03340.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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17
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Tersoff J, Jesson DE, Tang WX. Running Droplets of Gallium from Evaporation of Gallium Arsenide. Science 2009; 324:236-8. [DOI: 10.1126/science.1169546] [Citation(s) in RCA: 130] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Affiliation(s)
- J. Tersoff
- IBM Research Division, T. J. Watson Research Center, Yorktown Heights, NY 10598, USA
- School of Physics, Monash University, Victoria 3800, Australia
| | - D. E. Jesson
- IBM Research Division, T. J. Watson Research Center, Yorktown Heights, NY 10598, USA
- School of Physics, Monash University, Victoria 3800, Australia
| | - W. X. Tang
- IBM Research Division, T. J. Watson Research Center, Yorktown Heights, NY 10598, USA
- School of Physics, Monash University, Victoria 3800, Australia
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Schönhense G, Elmers H, Nepijko S, Schneider C. Time-Resolved Photoemission Electron Microscopy. ADVANCES IN IMAGING AND ELECTRON PHYSICS 2006. [DOI: 10.1016/s1076-5670(05)42003-0] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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