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1. Surface and bulk ferroelectric phase transition in super-tetragonal BiFeO 3 thin films

Author

D. Martinotti, Aymeric Vecchiola, Qiuxiang Zhu, Myriam Lachheb, Nicholas Barrett, Claire Mathieu, Christophe Lubin, Stéphane Fusil, Manuel Bibes, Xiaoyan Li-Bourrelier, A. Pancotti, Vincent Garcia, Qiang Wu, Alexandre Gloter, C. Carrétéro, Brahim Dkhil, Laboratoire de Physique des Solides (LPS), Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Unité mixte de physique CNRS/Thales (UMPhy CNRS/THALES), and THALES-Centre National de la Recherche Scientifique (CNRS)

Subjects
Kelvin probe force microscope, Materials science, Physics and Astronomy (miscellaneous), Condensed matter physics, Electron energy loss spectroscopy, 02 engineering and technology, 021001 nanoscience & nanotechnology, 01 natural sciences, Ferroelectricity, Tetragonal crystal system, Piezoresponse force microscopy, X-ray photoelectron spectroscopy, 0103 physical sciences, Scanning transmission electron microscopy, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Curie temperature, General Materials Science, 010306 general physics, 0210 nano-technology, ComputingMilieux_MISCELLANEOUS
Abstract

The temperature-dependent ferroelectric properties of super-tetragonal ${\mathrm{BiFeO}}_{3}$ are investigated using surface-sensitive low-energy electron microscopy (LEEM). We use epitaxial oxide ${\mathrm{BiFeO}}_{3}/{\mathrm{Ca}}_{0.96}{\mathrm{Ce}}_{0.04}{\mathrm{MnO}}_{3}$ bilayers grown by pulsed laser deposition on ${\mathrm{YAlO}}_{3}$ substrates. Ferroelectric, micrometer-scale domains are written by piezoresponse force microscopy and subsequently observed by LEEM from room temperature up to about 950 K. Kelvin probe force microscopy and LEEM spectroscopy reveal that the surface potential is efficiently (g50%) screened by adsorbates that are only released after annealing above 873 $\ifmmode\pm\else\textpm\fi{}$ 50 K in ultrahigh vacuum. The surface structure and chemistry of the ferroelectric thin films are analyzed using scanning transmission electron microscopy, electron energy loss spectroscopy, and x-ray photoelectron spectroscopy, discarding the occurrence of a putative ``skin layer'' effect. While its magnetic and structural transitions were reported in the literature, the true, ferroelectric Curie temperature of super-tetragonal ${\mathrm{BiFeO}}_{3}$ has not been determined so far. Here, we measure a Curie temperature of 930 $\ifmmode\pm\else\textpm\fi{}$ 30 K for the super-tetragonal ${\mathrm{BiFeO}}_{3}$ surface and corroborate it with volume-sensitive, temperature-dependent x-ray diffraction measurements. These results suggest that LEEM can be used as a powerful tool to probe surface charge and ferroelectric transitions in ultrathin films.

Published
2021
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2. Interaction of low-energy electrons with surface polarity near ferroelastic domain boundaries

Author

M Pellen, D. Martinotti, Ekhard K. H. Salje, Raphael Haumont, Ludovic Tortech, Z. Zhao, Qiang Wu, Nicholas Barrett, Xi'an University of Technology (XUT), Laboratoire d'Etude des NanoStructures et Imagerie de Surface (LENSIS), Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Laboratoire d'Electronique et nanoPhotonique Organique (LEPO), Laboratoire Innovation en Chimie des Surfaces et NanoSciences (LICSEN UMR 3685), Nanosciences et Innovation pour les Matériaux, la Biomédecine et l'Energie (ex SIS2M) (NIMBE UMR 3685), Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Institut de Chimie Moléculaire et des Matériaux d'Orsay (ICMMO), Université Paris-Sud - Paris 11 (UP11)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), University of Cambridge [UK] (CAM), Multi-disciplinary Materials Research Center, Frontier Institute of Science and Technology and State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, National Natural Science Foundation of China (Grant No. 51602255), Programs of Key Research and Development Plan of Shaanxi Province (Grant No. 2018ZDXM-GY-145), Scientific Research Program of Shaanxi Education Department (Grant No. 16JK1561), Doctoral Starting Fund of Xi’an University of Technology (Grant No. 101-451115016), Leverhulme Trust (Grant No. EM-2016-004), EPSRC (Grant No. EP/K009702/1), ANR-10-LABX-0035,Nano-Saclay,Paris-Saclay multidisciplinary Nano-Lab(2010), ANR-14-CE35-0019,HREELM,High resolution electron energy loss microscopy based on ionization of cold atoms: a new tool for surface nanochemistry(2014), Laboratoire Innovation en Chimie des Surfaces et NanoSciences (LICSEN), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Salje, Ekhard [0000-0002-8781-6154], and Apollo - University of Cambridge Repository

Subjects
Materials science, Physics and Astronomy (miscellaneous), 34 Chemical Sciences, Polarity (physics), Flexoelectricity, Ionic bonding, 02 engineering and technology, Electron, [CHIM.MATE]Chemical Sciences/Material chemistry, 021001 nanoscience & nanotechnology, Ridge (differential geometry), 01 natural sciences, Molecular physics, 0103 physical sciences, 3406 Physical Chemistry, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], General Materials Science, Surface charge, 010306 general physics, 0210 nano-technology, Crystal twinning, Electron scattering, 51 Physical Sciences
Abstract

International audience; We derive surface polarity at and near ferroelastic domain boundaries from molecular dynamics simulations based on an ionic spring model. Interatomic gradient forces lead to flexoelectricity which, in turn, generates polarity at the surface and in twin boundaries. We then derive generic properties of electron scattering spectra equivalent to those observed in low-energy electron microscopy (LEEM) and mirror electron microscopy (MEM) experiments. Negatively (positively) charged surfaces reflect (attract) incident electrons with low kinetic energy. The electron images reveal the valley and ridge surface structures near the intersection of the twin boundary and the surface. Polarity in surface layers is predicted to be visible in LEEM and MEM spectra at neutral surfaces, but much less when surfaces are charged. Inward polarity reflects electrons similar to negative surface charges, and outward polarity backscatters electrons like positive surface charges. Both the polarity in the twin boundary and the physical topography scatter electrons, consistent with experimental LEEM and MEM experiments on CaTiO3 with (001) and (111) surface terminations.

Published
2019
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3. Evidence for a surface anomaly during the cubic-tetragonal phase transition in BaTiO 3 (001)

Author

Nicholas Barrett, Cécile Mathieu, Ekhard K. H. Salje, J. Dionot, D. Martinotti, Laboratoire d'Etude des NanoStructures et Imagerie de Surface (LENSIS), Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Laboratoire d'Electronique et nanoPhotonique Organique (LEPO), and University of Cambridge [UK] (CAM)

Subjects
Surface (mathematics), [PHYS]Physics [physics], Phase transition, Materials science, Physics and Astronomy (miscellaneous), Condensed matter physics, 02 engineering and technology, 021001 nanoscience & nanotechnology, 01 natural sciences, Ferroelectricity, Tetragonal crystal system, Low-energy electron microscopy, Phase (matter), 0103 physical sciences, Perpendicular, Surface layer, 010306 general physics, 0210 nano-technology
Abstract

International audience; We have used low energy electron microscopy (LEEM) to study the evolution of the surface structure of BaTiO3(001) during the ferroelectric-paraelectric phase transition (120 °C, P4mm-Pm3m). Transient surface structures appear under heating at temperatures slightly above TC. Intersections between polar domain walls and the sample surface persist in the surface layer at 126.0 °C while the bulk has already transformed into the cubic phase. The wall signals are criss-crossed by a second set of stripe patterns with roughly perpendicular orientation at 126.3 °C. These surface patterns coarsen under further heating to 126.9 °C. The LEEM image is dominated in the ferroelectric state by intersections of ferroelastic/ferroelectric 90° walls and the surface. The intersection lines are charged.

Published
2018
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4. Control of surface potential at polar domain walls in a nonpolar oxide

Author

Claire Mathieu, Jens Kreisel, D. Martinotti, Ludovic Tortech, Ekhard K. H. Salje, Pierre-Yves Hicher, Mael Guennou, Guillaume F. Nataf, Raphael Haumont, Nick Barrett, Oktay Aktas, Laboratoire d'Etude des NanoStructures et Imagerie de Surface (LENSIS), Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Luxembourg Institute of Science and Technology (LIST), Physics and Materials Science Research Unit, University of Luxemburg, Laboratoire de Physico-Chimie de l'Etat Solide (CHIMSOL), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), Department of Earth Sciences [University of Cambridge], University of Cambridge [UK] (CAM), Laboratoire Innovation en Chimie des Surfaces et NanoSciences (LICSEN UMR 3685), Nanosciences et Innovation pour les Matériaux, la Biomédecine et l'Energie (ex SIS2M) (NIMBE UMR 3685), Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Institut Parisien de Chimie Moléculaire (IPCM), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Electronique et nanoPhotonique Organique (LEPO), Nataf, Guillaume [0000-0001-9215-4717], Salje, Ekhard [0000-0002-8781-6154], Apollo - University of Cambridge Repository, Centre National de la Recherche Scientifique (CNRS)-Université Paris-Sud - Paris 11 (UP11), Department of Earth Sciences, University of Cambridge, Laboratoire Innovation en Chimie des Surfaces et NanoSciences (LICSEN), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut Rayonnement Matière de Saclay (IRAMIS), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)

Subjects
Materials science, Physics and Astronomy (miscellaneous), FOS: Physical sciences, 02 engineering and technology, 01 natural sciences, Condensed Matter::Materials Science, chemistry.chemical_compound, Electric field, 0103 physical sciences, Microelectronics, General Materials Science, 010306 general physics, [PHYS]Physics [physics], Condensed Matter - Materials Science, Condensed matter physics, business.industry, Materials Science (cond-mat.mtrl-sci), 021001 nanoscience & nanotechnology, Polarization (waves), Ferroelectricity, Piezoelectricity, cond-mat.mtrl-sci, Calcium titanate, Ferromagnetism, chemistry, Polar, 0210 nano-technology, business
Abstract

Ferroic domain walls could play an important role in microelectronics, given their nanometric size and often distinct functional properties. Until now, devices and device concepts were mostly based on mobile domain walls in ferromagnetic and ferroelectric materials. A less explored path is to make use of polar domain walls in nonpolar ferroelastic materials. Indeed, while the polar character of ferroelastic domain walls has been demonstrated, polarization control has been elusive. Here, we report evidence for the electrostatic signature of the domain-wall polarization in nonpolar calcium titanate (CaTiO3). Macroscopic mechanical resonances excited by an ac electric field are observed as a signature of a piezoelectric response caused by polar walls. On the microscopic scale, the polarization in domain walls modifies the local surface potential of the sample. Through imaging of surface potential variations, we show that the potential at the domain wall can be controlled by electron injection. This could enable devices based on nondestructive information readout of surface potential., Comment: 30 pages, 12 figures

Published
2017
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5. Adsorbate Screening of Surface Charge of Microscopic Ferroelectric Domains in Sol–Gel PbZr$_{0.2}$ Ti$_{0.8}$ O$_3$ Thin Films

Author

O. Copie, Olivier Renault, Sara Gonzalez, Nicholas Barrett, Nicolas Chevalier, Claire Mathieu, D. Martinotti, Cindy L. Rountree, Gwenael Le Rhun, Institut Jean Lamour (IJL), Institut de Chimie du CNRS (INC)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Etude des NanoStructures et Imagerie de Surface (LENSIS), Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Commissariat à l'énergie atomique et aux énergies alternatives - Laboratoire d'Electronique et de Technologie de l'Information (CEA-LETI), Direction de Recherche Technologique (CEA) (DRT (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Systèmes Physiques Hors-équilibre, hYdrodynamique, éNergie et compleXes (SPHYNX), Laboratoire d'Electronique et nanoPhotonique Organique (LEPO), The CEA Nanoscience program, IMPACT N4S, ANR-15-IDEX-0004,LUE,Isite LUE(2015), and Université de Lorraine (UL)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Materials science, PZT, Analytical chemistry, 02 engineering and technology, Electron, PFM, 01 natural sciences, law.invention, PEEM, law, 0103 physical sciences, surface, General Materials Science, Surface charge, Thin film, 010306 general physics, Polarization (electrochemistry), Sol-gel, LEEM, [PHYS]Physics [physics], polarization, Condensed matter physics, screening, 021001 nanoscience & nanotechnology, Ferroelectricity, Curie temperature, Electron microscope, AFM, 0210 nano-technology
Abstract

International audience; We present a study of adsorbate screening of surface charge in microscopic ferroelectric domains in a sol−gel grown PbZr$_{0.2}$ Ti$_{0.8}$ O$_3$ thin film. Low-energy and photoemission electron microscopies were employed to characterize the temperature dependence of surface charge and polarization of ferroelectric domains written by atomic force microscopy. We study the role of charged adsorbates in screening of polarization-bound charges. We demonstrate that full-field electron microscopy is suitable for the determination of ferroelectric system properties such as the Curie temperature.

Published
2017
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6. Local investigation of the emissive properties of LaB$_6$–ZrB$_2$ eutectics

Author

Steven B. Fairchild, D. Martinotti, Ludovic Douillard, Ali Sayir, John J. Boeckl, Tyson C. Back, Marie-Hélène Berger, V. Filipov, Patrick Soukiassian, Centre des Matériaux (MAT), MINES ParisTech - École nationale supérieure des mines de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), University of Dayton, Air Force Research Laboratory (AFRL), United States Air Force (USAF), Laboratoire d'Etude des NanoStructures et Imagerie de Surface (LENSIS), Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Laboratoire d'Electronique et nanoPhotonique Organique (LEPO), National Academy of Sciences of Ukraine (NASU), NASA Glenn Research Center, NASA, Centre des Matériaux (CDM), and Mines Paris - PSL (École nationale supérieure des mines de Paris)

Subjects
010302 applied physics, [PHYS]Physics [physics], Work (thermodynamics), Materials science, business.industry, Mechanical Engineering, Diffusion, Composite number, 02 engineering and technology, 021001 nanoscience & nanotechnology, 01 natural sciences, law.invention, Optics, Mechanics of Materials, law, 0103 physical sciences, General Materials Science, Work function, Fiber, Electron microscope, Composite material, 0210 nano-technology, business, Eutectic system, Directional solidification
Abstract

International audience; LaB$_6$–ZrB$_2$ composites obtained by directional solidification at eutectic composition have been investigated by low-energy electron microscopy (LEEM) and thermal emission electron microscopy (ThEEM). The transitions from the mirror electron microscopy mode to the LEEM mode for the hexa- and diborides indicate lower work functions of the two phases when embedded in the composite compared to the corresponding single phases. In the composite, the work function of the ZrB2 fibers is similar to that of the matrix and ThEEM images display a brighter contrast for the fibers. This is explained by the thermally activated diffusion of La on the fiber surface.

Published
2017
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7. Low energy electron imaging of domains and domain walls in magnesium-doped lithium niobate

Author

Claire Mathieu, Mael Guennou, Cindy L. Rountree, Guillaume F. Nataf, Patrick Grysan, D. Martinotti, Nicholas Barrett, Jens Kreisel, Laboratoire d'Etude des NanoStructures et Imagerie de Surface (LENSIS), Service de physique de l'état condensé (SPEC - UMR3680), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Institut Rayonnement Matière de Saclay (IRAMIS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Materials Research and Technology (MRT) Department, Luxembourg Institute of Science and Technology (LIST), Physics and Materials Science Research Unit, University of Luxemburg, Laboratoire d'Electronique et nanoPhotonique Organique (LEPO), and Systèmes Physiques Hors-équilibre, hYdrodynamique, éNergie et compleXes (SPHYNX)

Subjects
[PHYS]Physics [physics], 010302 applied physics, Multidisciplinary, Materials science, Condensed matter physics, Band gap, Doping, Lithium niobate, Physics [G04] [Physical, chemical, mathematical & earth Sciences], 02 engineering and technology, Electron, 021001 nanoscience & nanotechnology, 01 natural sciences, Ferroelectricity, Article, law.invention, chemistry.chemical_compound, Low-energy electron microscopy, Physique [G04] [Physique, chimie, mathématiques & sciences de la terre], chemistry, law, Electric field, 0103 physical sciences, Electron microscope, 0210 nano-technology
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.

Published
2016
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9. A novel method to determine the Ehrlich–Schwoebel barrier

Author

H.-J. Ernst, T. Maroutian, R Gerlach, D Martinotti, and Ludovic Douillard

Subjects
Range (particle radiation), Chemistry, business.industry, Nucleation, chemistry.chemical_element, Surfaces and Interfaces, Substrate (electronics), Atmospheric temperature range, Condensed Matter Physics, Molecular physics, Copper, Surfaces, Coatings and Films, law.invention, Flux (metallurgy), Optics, Transition metal, law, Materials Chemistry, Electron microscope, business
Abstract

The homoepitaxial growth of Cu on Cu(0 0 1) has been investigated with low-energy electron microscopy (LEEM). The temporal evolution of engineered pyramid-like structures has been monitored for a range of incident Cu fluxes and substrate temperatures. The step velocities have been analyzed in the framework of a novel growth model that contains as the only adjustable parameter the height of the Ehrlich–Schwoebel (ES) barrier. The simultaneous description of all step velocities observed within the flux and temperature range covered by our experiments determines the height of the ES barrier to about 125 meV in this system.

Published
2001
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10. From CdTe/Fe schottky barrier to Cd1−xFexTe semimagnetic semiconductor

Author

Bogdan J. Kowalski, B.A. Orlowski, J.-P. Lacharme, Rachid Belkhou, Nicholas Barrett, C.A. Sébenne, Elzbieta Guziewicz, D. Martinotti, C. Guillot, and D. Radosavkic

Subjects
Chemistry, business.industry, Annealing (metallurgy), Schottky barrier, Analytical chemistry, General Physics and Astronomy, Heterojunction, Surfaces and Interfaces, General Chemistry, Condensed Matter Physics, Surfaces, Coatings and Films, Semiconductor, Transition metal, X-ray photoelectron spectroscopy, Monolayer, Ternary operation, business
Abstract

Synchrotron radiation tuned to the Fe 3p–3d transition (hv = 56eV) was used to study Fano type resonant photoemission spectra for a clean CdTe(110) surface sequentially covered in the monolayer (ML) range by Fe atoms and annealed. The results showed that, in the first stage of the deposition, the Fe atoms are mainly involved in the creation of a Cd1−xFexTe ternary crystal (0.2–0.6 ML). At higher coverages (1.2 ML), the contribution of Fe metallic islands becomes visible. CdTe dissociation in the surface region leads to the appearance of Cd Fe interaction at higher Fe deposition (3.6 ML). After deposition of 20 ML, sample annealing in the 300°C range leads to Fe diffusion into the crystal and the measured spectra correspond well to the Cd1−xFexTe calculated spectra.

Published
1998
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12. Valence band of in resonant photoemission spectra

Author

C.A. Sébenne, D. Martinotti, C. Guillot, Nicholas Barrett, Bogdan J. Kowalski, J.-P. Lacharme, and B.A. Orlowski

Subjects
Chemistry, General Physics and Astronomy, Resonance, Synchrotron radiation, Surfaces and Interfaces, General Chemistry, Condensed Matter Physics, Spectral line, Surfaces, Coatings and Films, Crystal, Crystallography, X-ray photoelectron spectroscopy, Atom, Density of states, Thin film
Abstract

Valence band of Cd 1-x Fe x Se/Fe in resonant photoemission spectra Resonant photoemission spectra of Fe atoms (3p-3d) were measured for freshly cleaved Cd 0-86 Fe 0.14 Se crystal (110) surface and for the same surface with sequentially deposited Fe atoms in the range 0.3-80 ML. The synchrotron radiation (LURE, Orsay, France) was used to measure valence band density of state distributions and Cd 4d core level for the radiation energy range 50-60 eV, which includes the Fe 3p-3d resonant energy equal to 56 eV. At the lowest stages of Fe atom deposition (up to about 3 ML), Fe atoms replace Cd atoms in the crystal, making a Cd 1-x Fe x Se alloy with a higher x and leaving extra Cd as small islands or clusters. For the next stages of Fe deposition (about 3-10 ML) the dissociated Cd atoms create a Cd-Fe alloy. At higher stages of Fe deposition (above about 10 ML) a Fe thin film is formed.

Published
1996
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13. Effects of laser irradiation on the morphology of Cu(110)

Author

D. Martinotti, Johannes Heitz, H.-J. Ernst, P. Zeppenfeld, T. Brandstetter, M. Draxler, T. Stehrer, Michael Hohage, and N. Georgiev

Subjects
Diffraction, Materials science, business.industry, Condensed Matter Physics, Laser, Crystallographic defect, Molecular physics, Electronic, Optical and Magnetic Materials, law.invention, Optics, Electron diffraction, law, Irradiation, Reflectance difference spectroscopy, Scanning tunneling microscope, Dislocation, business
Abstract

The effects of pulsed laser irradiation on the morphology of the Cu(110) surface were investigated by means of reflectance difference spectroscopy (RDS) and spot profile analysis low-energy electron diffraction (SPA-LEED). The laser light induces surface defects (adatoms and islands) as well as subsurface dislocation lines. The high surface mobility leads to efficient annealing of the surface defects even at room temperature, whereas the subsurface dislocation lines persist up to temperatures T>800 K. SPA-LEED profiles of the (00) diffraction spot from the laser irradiated surface suggest an anisotropic distribution of the subsurface line defects related to the geometry of the fcc easy glide system, which is corroborated by STM measurements. Comparative experiments using conventional Ar ion bombardment point out the distinctiveness of the morphological changes induced by laser irradiation.

Published
2008
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14. Enhanced photoemission from localized inhomogeneities on Cu(001) characterized by laser-assisted photoemission electron microscopy and low-energy electron microscopy

Author

D. Martinotti, N. Georgiev, and H.-J. Ernst

Subjects
Photoemission electron microscopy, Low-energy electron microscopy, Materials science, Inverse photoemission spectroscopy, Surface plasmon, Ultraviolet light, Energy filtered transmission electron microscopy, Angle-resolved photoemission spectroscopy, Atomic physics, Condensed Matter Physics, Dark field microscopy, Electronic, Optical and Magnetic Materials
Abstract

Multiphoton photoelectron emission from a state-of-the-art prepared Cu(001) surface has been investigated with photoemission electron microscopy. Randomly distributed, spatially confined regions (about $1\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{m}$ in diameter) of intense electron yield (hot spots) are observed. The hot spots give rise to distortions of the corresponding low-energy electron microscopy image. They are identified as polycrystallinelike protrusions embedded in the surface. The density of these inhomogeneities is about $2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}{\mathrm{m}}^{2}$ and cannot be manipulated by ion bombardment or by homoepitaxial growth. The response of hot spots to illumination under ultraviolet light produced by an arc lamp and illumination by blue and infrared femtosecond laser light for different polarizations is recorded from the same surface region, allowing for a direct comparison. Hot spots respond very efficiently and even stronger to $s$-polarized light as compared to $p$-polarized light, and show apparently a nonresonant behavior with respect to the exciting wavelength. We discuss some of the conceivable mechanisms underlying this anomalous photoemission, also in view of the particular characteristics that are specific to our experimental setup. Our data are not compatible with an interpretation which relies exclusively on the excitation of (localized) surface plasmon modes, but rather with a nonresonant near-zone light field enhancement.

Published
2007
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15. Multilayer epitaxial graphene grown on the surface; structure and electronic properties

Author

Antonio Tejeda, E. H. Conrad, Patrick Soukiassian, D. Martinotti, J. Hass, Jeremy Hicks, M. C. Clark, P. Le Fèvre, François Bertran, Mike Sprinkle, Amina Taleb-Ibrahimi, and Holly N. Tinkey

Subjects
Materials science, Acoustics and Ultrasonics, Graphene, Stacking, Nanotechnology, Electronic structure, Condensed Matter Physics, Surfaces, Coatings and Films, Electronic, Optical and Magnetic Materials, law.invention, chemistry.chemical_compound, chemistry, law, Silicon carbide, Graphite, Thin film, Bilayer graphene, Graphene nanoribbons
Abstract

We review the progress towards developing epitaxial graphene as a material for carbon electronics. In particular, we discuss improvements in epitaxial graphene growth, interface control and the understanding of multilayer epitaxial graphene's (MEG's) electronic properties. Although graphene grown on both polar faces of SiC will be discussed, our discussions will focus on graphene grown on the C-face of SiC. The unique properties of C-face MEG have become apparent. These films behave electronically like a stack of nearly independent graphene sheets rather than a thin Bernal stacked graphite sample. The origins of multilayer graphene's electronic behaviour are its unique highly ordered stacking of non-Bernal rotated graphene planes. While these rotations do not significantly affect the inter-layer interactions, they do break the stacking symmetry of graphite. It is this broken symmetry that leads to each sheet behaving like isolated graphene planes.

Published
2010
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17. Multilayer epitaxial graphene grown on the ({\rm SiC}\,\,000\bar{1}) surface; structure and electronic properties.

Author

M Sprinkle, J Hicks, A Tejeda, A Taleb, P Le Fevre, F Bertran, H Tinkey, M C Clark, P Soukiassian, D Martinotti, J Hass, and E H Conrad

Subjects
GRAPHENE, EPITAXY, ELECTRONIC structure, CARBON, MULTILAYERED thin films, GRAPHITE, SYMMETRY breaking, SILICON carbide, SURFACES (Physics)
Abstract

We review the progress towards developing epitaxial graphene as a material for carbon electronics. In particular, we discuss improvements in epitaxial graphene growth, interface control and the understanding of multilayer epitaxial graphene's (MEG's) electronic properties. Although graphene grown on both polar faces of SiC will be discussed, our discussions will focus on graphene grown on the (0\,0\,0\,\bar{1}) C-face of SiC. The unique properties of C-face MEG have become apparent. These films behave electronically like a stack of nearly independent graphene sheets rather than a thin Bernal stacked graphite sample. The origins of multilayer graphene's electronic behaviour are its unique highly ordered stacking of non-Bernal rotated graphene planes. While these rotations do not significantly affect the inter-layer interactions, they do break the stacking symmetry of graphite. It is this broken symmetry that leads to each sheet behaving like isolated graphene planes. [ABSTRACT FROM AUTHOR]

Published
2010
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18. Adsorbate Screening of Surface Charge of Microscopic Ferroelectric Domains in Sol-Gel PbZr 0.2 Ti 0.8 O 3 Thin Films.

Author

Copie O, Chevalier N, Le Rhun G, Rountree CL, Martinotti D, Gonzalez S, Mathieu C, Renault O, and Barrett N

Abstract

We present a study of adsorbate screening of surface charge in microscopic ferroelectric domains in a sol-gel grown PbZr 0.2 Ti 0.8 O 3 thin film. Low-energy and photoemission electron microscopies were employed to characterize the temperature dependence of surface charge and polarization of ferroelectric domains written by atomic force microscopy. We study the role of charged adsorbates in screening of polarization-bound charges. We demonstrate that full-field electron microscopy is suitable for the determination of ferroelectric system properties such as the Curie temperature.

Published
2017
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