A5076339122- Surface and Thin Film Phenomena
- Magnetic properties of thin films
- Electron and X-Ray Spectroscopy Techniques
- Semiconductor materials and interfaces
- Semiconductor materials and devices
- Quantum and electron transport phenomena
- ZnO doping and properties
- Electronic and Structural Properties of Oxides
- Magnetic Properties and Applications
- Magnetic and transport properties of perovskites and related materials
- Advanced Electron Microscopy Techniques and Applications
- Advanced Materials Characterization Techniques
- Semiconductor Quantum Structures and Devices
- Copper Interconnects and Reliability
- 2D Materials and Applications
- Magnetic Properties of Alloys
- Heusler alloys: electronic and magnetic properties
- Advanced Chemical Physics Studies
- Metal and Thin Film Mechanics
- Force Microscopy Techniques and Applications
- Graphene research and applications
- Molecular Junctions and Nanostructures
- Conducting polymers and applications
- Nanowire Synthesis and Applications
- Magnesium Oxide Properties and Applications
Université de Rennes
2013-2024
Centre National de la Recherche Scientifique
2013-2024
Institut de Physique de Rennes
2014-2024
Université Rennes 2
2024
Université Toulouse III - Paul Sabatier
2020
Centre d’Élaboration de Matériaux et d’Études Structurales
2020
Université de Toulouse
2020
Laboratoire de Physique des Interfaces et des Couches Minces
2005
Laboratoire de Photochimie et d'Ingénierie Macromoléculaire
1996-2002
Laboratoire de Spectrométrie Ionique et Moléculaire
1997
Grazing incidence x-ray diffraction study of Fe epitaxial ultrathin films (1.5-13 nm) on GaAs (001) reveals an anisotropy both domain shape and strain, with [110] [1-10] as the principal directions. It is shown that observed thickness-dependent strain anisotropy, together a uniaxial interface term, can provide unambiguous explanation to usual in-plane magnetic its thickness dependence in this thin-film system.
The electronic band structure and the work function of MgO thin films epitaxially grown on Ag(001) have been investigated using x-ray ultraviolet photoelectron spectroscopy for various oxide thicknesses. deposition induces a strong diminution in metal function. p-type Schottky barrier height is constant at 3.85±0.10 eV above two monolayers experimental value ionization potential 7.15±0.15 eV. Our results are well consistent with description terms Schottky–Mott model corrected by an...
The electronic band structure at the interface of MgO-GaAs(001) tunnel contact has been experimentally studied. X-ray photoelectron spectroscopy used to measure valence-band offset heterojunction interface. ΔEV is determined be 4.2±0.1eV. As a consequence, nested “type-I” alignment with conduction-band ΔEC=2.2±0.1eV found. accurate determination valence and conduction offsets important for fundamental understanding spin injection in GaAs.
Hybrid materials taking advantage of the different physical properties are highly attractive for numerous applications in today's science and technology. Here, it is demonstrated that epitaxial bi-domain III-V/Si hybrid structures, composed bulk photo-active semiconductors with 2D topological semi-metallic vertical inclusions, endowed ambipolar properties. By combining structural, transport, photoelectrochemical characterizations first-principle calculations, shown able within same layer to...
By combining x-ray excited Auger electron diffraction experiments and multiple scattering calculations we reveal a layer-resolved shift for the Mg $K{L}_{23}{L}_{23}$ transition in MgO ultrathin films (4--6 \AA{}) on Ag(001). This resolution is exploited to demonstrate possibility of controlling atom incorporation at $\mathrm{MgO}/\mathrm{Ag}(001)$ interface by exposing flux. A substantial reduction work function observed during exposition phase reflects both band-offset variations band...
The properties of MgO/Ag(001) ultrathin films with substitutional Mg atoms in the interface metal layer have been investigated by means Auger electron diffraction experiments, ultraviolet photoemission spectroscopy, and density functional theory (DFT) calculations. Exploiting layer-by-layer resolution $\mathrm{Mg}\phantom{\rule{0.28em}{0ex}}K{L}_{23}{L}_{23}$ spectra using multiple scattering calculations, we first determine interlayer distances as well morphological parameters system...
Using angle-resolved photoemission spectroscopy, combined with first principle and coupled self-consistent Poisson-Schr\"odinger calculations, we demonstrate that potassium (K) atoms adsorbed on the low-temperature phase of $1T\text{\ensuremath{-}}{\mathrm{TiSe}}_{2}$ induce creation a two-dimensional electron gas (2DEG) quantum confinement its charge-density wave (CDW) at surface. By further changing K coverage, tune carrier density within 2DEG allows us to nullify, surface, electronic...
We have carefully investigated the possibility of preparing a well-ordered $p(1\ifmmode\times\else\texttimes\fi{}1)$ two-dimensional Mn monolayer on Ag(001) by means photoelectron diffraction. It is found that flat (ML) with good degree perfection actually achieved deposition at low rates (typically 0.1--0.2 ML/min) substrate held 80 K. Substrate temperatures higher than $\ensuremath{\sim}130\mathrm{K}$ invariably result in exchange adatoms Ag and formation surface alloy. Valence-band...
In view of future spintronic and spin-optronic devices, such as spin light-emitting diodes lasers, it is important to understand the dependence electrical injection on bias in bipolar devices based GaAs. Focusing efficiency Co-Fe-B/MgO injectors, authors investigate influence MgO growth process this dependence, using tunnel barriers fabricated by different techniques. The efficiency, compromise between high intensity circular polarization electroluminescence, depend strongly characteristics...
The interface resistance at metal/semiconductor junctions has been a key issue for decades. control of this is dependent on the possibility to tune Schottky barrier height. However, Fermi level pinning in these systems forbids total over resistance. introduction 2D crystals between semiconductor surfaces and metals may be an interesting route towards goal. In work, we study influence graphene monolayer metal silicon We used X-ray photoemission spectroscopy rule out presence oxides interface,...
The luminescence of SrTiO3 depends on the sample type, either doped or stoichiometric, as grown treated, excitation conditions, and temperature. origin emissions, blue, green, infrared, remains controversial. In particular, role played by defects, mainly oxygen vacancies, impurities, self-trapped holes electrons different emissions are far to be elucidated. We present a cathodoluminescence (CL) photoluminescence (PL) study undoped Nb-doped samples. conditions CL PL permit distinguish...
We have probed the interface of a ferromagnetic/semiconductor (FM/SC) heterojunction by combined high resolution photoemission spectroscopy and x-ray photoelectron diffraction study. $\mathrm{Fe}∕\mathrm{Zn}\mathrm{Se}(001)$ is considered as an example very low reactivity system it expected to constitute large tunnel magnetoresistance devices. focus on atomic environment, microscopic processes formation iron valence band. show that Fe contact with ZnSe induces chemical conversion outermost...
The electronic band structure in the epitaxial Fe∕MgO∕GaAs(001) tunnel junction has been studied by x-ray and ultraviolet photoelectron spectroscopy measurements. Schottky barrier height (SBH) of Fe on MgO∕GaAs heterostructure is determined to be 3.3±0.1eV, which sets Fermi level at about 0.3eV above GaAs valence maximum. This SBH also exactly same as that measured from MgO monocrystal. After deposition, no bending change observed underlayers. On contrary, Au Al depositions led clear...
The electrical properties of Au∕MgO∕n-GaAs(001) tunnel structures have been investigated with capacitance-voltage and current-voltage measurements at room temperature various MgO thicknesses between 0.5 6.0nm. For an oxide thickness higher than 2nm for low bias voltages, the voltage essentially drops across structure progressively enters high-current mode operation increasing reverse voltage, property sought in spin injection devices. In this mode, we demonstrate that a large amount charge...
The role of epitaxial strain for the in-plane magnetic anisotropies is studied Fe(001) thin films (0.9--60 nm) deposited by molecular-beam epitaxy at room temperature on ${\text{Al}}_{0.48}{\text{In}}_{0.52}\text{As}(001)$ layers. correlation between structural and properties has been investigated using ex situ x-ray diffraction (XRD) experiments magneto-optical Kerr effect (MOKE) measurements. Fe grows in a body-centered-cubic (bcc) structure with relationship...
The spatially resolved electronic structure of the epitaxial Au/MgO/GaAs(001) tunnel junction has been studied by ballistic electron emission microscopy. Schottky barrier height Au on MgO/GaAs heterostructure is determined to be 3.90 eV, in good agreement with averaged x-ray photoelectron spectroscopy measurements. Locally, two well-defined conduction channels are observed for electrons energies 2.5 and 3.8 i.e., below band minimum oxide layer. These attributed defect states band-gap related...
We present an experimental investigation of the interface electronic structure thin MgO films epitaxially grown on Ag(001) by x-ray and ultraviolet photoemission spectroscopy as a function oxide growth conditions. It is shown that Schottky barrier height at MgO/metal can be tuned over 0.7 eV modification oxygen partial pressure or sample temperature. These results are explained in framework extended Schottky-Mott model MgO-induced polarization effect Mg enrichment silver surface region.
Due to the difficulty grow high quality semiconductors on ferromagnetic metals, study of spin diffusion transport in Si was only limited lateral geometry devices. In this work, by using ultra-high vacuum wafer-bonding technique, we have successfully fabricated metal semiconductor CoFeB/MgO/Si/Pt vertical structures. We hereby demonstrate pure spin-current injection and perpendicular current flow over a distance larger than 2\mu m n-type at room temperature. those experiments, propagating is...
Ultrathin Mn films deposited at room temperature (RT) in ultrahigh vacuum on Ag(100) were investigated using ion scattering spectroscopy (ISS), angle-resolved ultraviolet photoemission (ARUPS) and low-energy electron diffraction (LEED). Up to \ensuremath{\sim}1 ML, ISS ARUPS definitely indicate that the Mn/Ag(100) interface is unstable RT. We find with time an Ag enrichment of film surface takes place eventually formation a two-dimensional (2D) p(1\ifmmode\times\else\texttimes\fi{}1) layer...
We present a dynamical low-energy electron diffraction analysis of the atomic and magnetic structure obtained by deposition 0.9 Mn monolayers on Ag(001) held at 100 K. find that film grows in an essentially flat ideal monoatomic layer with located fourfold hollow sites substrate undergoes no sizeable reconstruction its topmost layers. The Mn-Ag interlayer distance ${d}_{12}=2.00\ifmmode\pm\else\textpm\fi{}0.03\AA{}$ is found to be much larger than \ensuremath{\sim}1.85 \AA{} expected from...
We report on ballistic electron-emission spectroscopy high-quality Au(110)/GaAs(001) and Fe(001)/GaAs(001) Schottky contacts. For the interface, current is characterized by a strong electron injection in $L$ valley of GaAs conduction band. This remarkable spectroscopic feature absent for interface. These observations are explained different electronic structures two metal layers, assuming conservation transverse momentum at metal/semiconductor epitaxial interfaces. Conversely, this...
The mechanisms governing the formation of Schottky barriers at graphene/hydrogen-passivated silicon interfaces where graphene plays role a two-dimensional (2D) metal electrode have been investigated by means x-ray photoemission spectroscopy and density functional theory (DFT) calculations. To control work function without altering either structure or band dispersion we used method that consists in depositing small amounts gold forming clusters on system under an ultra-high-vacuum...
We have investigated the interface formation at room temperature between Fe and ${\mathrm{TiO}}_{2}$-terminated ${\mathrm{SrTiO}}_{3}(001)$ surface using x-ray photoelectron spectroscopy. Oxygen vacancies within ${\mathrm{SrTiO}}_{3}$ lattice in first planes beneath $\mathrm{Fe}\text{/}{\mathrm{SrTiO}}_{3}$ are induced by deposition. Through a detailed analysis of $2p$, Sr $3d$, Ti $2p$ core-level line shapes we propose quantitative description impact on electronic properties system. While...