Structure et Dynamique des Surfaces

Responsable : Frédéric Leroy

Présentation

Our group at CINaM mainly studies mechanisms taking place at surfaces of crystalline materials with a particular emphasis on the real-time and in-situ characterization and modeling of the observed phenomena influencing the structural and electronic properties.

Our research mainly involves an experimental set-up including Low-Energy Electron Microscopy / Photo-Emission Electron Microscopy (LEEM/PEEM) and local probe microscopies (Scanning Tunneling Microscopy / Atomic Force Microscopy-STM/AFM).

Structure Surface et Dynamique 3

News
03.2020
We are looking for PhD candidates to work with us on 2D materials.
Dynamics at surfaces

We study using LEEM different surface processes  in real time and in operando such as surface reconstructions, epitaxial growth, step dynamics, thermal decomposition of Si oxyde layers, self-propelled motion of nanoparticles, surface preparation for microelectronic devices ….

For a couple of years, we have been studying in details the spontaneous motion of solid or liquid droplets induced by interfacial reactivity and/or electromigration. The systems under study are Si/SiO2, Au/Si and Au/Ge.

 

Structure Surface et Dynamique 4
AuSi eutectic droplet climbing steps on a Si(111) surface. Surf. Sci. 632 (2015) 1
Triple-line control


The description of the triple line at the substrate-film-vacuum interface is one of the fundamental issues in wetting statics and dynamics and has been the subject of a large literature in the case of liquids. However, though solid films are the basic component of many technological devices, there is still a lack of understanding about the triple line in solids, especially in non-equilibrium situations.

Our approach of the statics and dynamics of the solid-solid-vacuum triple line is based on three underlying questions: (i) How does non-equilibrium conditions, modify the usual equilibrium Young equation? (ii) What is the influence of chemical reactivity at the triple line? (iii) What is the role of substrate heterogeneity on the triple line behavior?
For this purpose, we combine LEEM/PEEM and STM/AFM to follow in situ several phenomena linked to the triple line behavior such as:  solid-state dewetting (study of SOI or GeOI ultra-thin films), void opening (thermal decomposition of SiO2), self-propelled behavior of 3D liquids or solids droplets (Au/Si, Au/Ge,Si/SiO2…), island spreading….
Associated theoretical calculations and/or simulations  (Kinetic Monte Carlo, continuum models) are  performed in collaboration with O. Pierre-Louis from Institut Lumière-Matière (Lyon).

The ultimate goal is to use these results to propose novel strategies to control the morphology and the stability of nanostructures.

Funding: ANR grant LOTUS
Collaborations:
  • O. Pierre-Louis (ILM, Lyon)
  • C. Barbé & Ł. Borowik (CEA/LETI, Grenoble)
  • Y. Saito (Keio Univ., Japan)
  • C. V. Thompson (MIT, Cambridge, USA)

 

Structure Surface et Dynamique 5
Receding solid-solid-vacuum triple line (red line) in the case of a solid-state dewetting.
Surf. Sci. Rep. 71 (2016) 391
LEEM development


The demand for advanced characterization tools applied to nanomaterials promotes the development of new microscopy techniques. In that perspective we aim at developing an instrument combining holography with low-energy electrons in reflection geometry. Low-Energy Electron Microscopy (LEEM) is based on wave optics however as a conventional electron-optical technique all the information on the phase is lost in the recording process. Since the seminal work of Aharonov and Bohm and the tremendous advances in transmission electron microscopy holography, pure phase objects such as magnetic or electric stray fields as well as strain fields induced by single defects are now measured.

We propose to take advantage of the reflection geometry working with low energy electrons to measure the phase of the reflected and diffracted waves by designing and implementing electrostatic biprisms in a LEEM to achieve a new imaging mode based on off-axis holography. To explore the full potential of this technique, we will address in situ key nanomaterial properties at surfaces: charge transfers at semiconducting and insulating materials surfaces, ferromagnetism, and surface strain induced by structural defects such as dislocations.

Funding: ANR grant HoloLEEM
Collaborations:

F. Houdelier (CEMES, Toulouse)

 

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Scheme of an electron biprism.
From Adv. in Phys. 41 (1992) 59
2D Materials


Graphene (a single atomic plane of carbon) and graphene-like materials (nano-sheets of layered materials with a honey-comb atomic structure similar to grahene) are increasingly studied for their potential technological integration.
Despite the huge effort placed on the optical and electronic characterization of these material, little is known regarding the atomic growth mecanisms and the structure-properties interplay.

Various systems (Graphene, MoS2, …) are currently being explored within the group or in collaborations with different elaboration approaches (in situ growth, CVD, exfoliation).

Collaborations:
  • A. Michon & M. Portail (CHREA, Toulouse)
  • J. Coraux (Institut Néel, Grenoble)
Structure Surface et Dynamique 7
A. Geim and K. Novoselov: 2010 Physics Nobel Prize Laureates « for groundbreaking experiments regarding the two-dimensional material graphene »
Elasticity


Our goal is to describe elastic properties of surfaces from theoretical (concepts of surface stress, surface strain, surface elastic constants, …) and experimental (step-induced elastic relaxation measured by grazing incidence x-ray diffraction) point of views. Applications are also studied (epitaxial growth, nanoelasticity, surface instabilities, …).

Collaborations:
  • G. Prévot (INSP, Paris)
  • B. Ranguelov, M. Michailov (IPC, BAS, Bulgary)
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Cross sections of the displacement fields induced by a double step on a vicinal surface of a Si(001) substrate. Phys. Rev. B 93 (2016) 045416

 

Publications

2020

2D Manipulation of Nanoobjects by Perpendicular Electric Fields: Implications for Nanofabrication

Stefano Curiotto, F. Cheynis, Pierre Müller, Frédéric Leroy

Acs Applied Nano Materials 3:1118-1122 (2020)10.1021/acsanm.9b02517

2019

2D nanostructure motion on anisotropic surfaces controlled by electromigration

Stefano Curiotto, Pierre Müller, Ali El-Barraj, Fabien Cheynis, Olivier Pierre-Louis, Frédéric Leroy

Applied Surface Science 469 (2019)10.1016/j.apsusc.2018.11.049

Shape changes of two-dimensional atomic islands and vacancy clusters diffusing on epitaxial (1 1 1) interfaces under the impact of an external force

Stefano Curiotto, Frédéric Leroy, Pierre Muller, Fabien Cheynis, Michail Michailov, Ali El-Barraj, Bogdan Ranguelov

Journal of Crystal Growth 520:42-45 (2019)10.1016/j.jcrysgro.2019.05.016

Atomic Transport in Au-Ge Droplets: Brownian and Electromigration Dynamics

Frédéric Leroy, Ali El-Barraj, Pierre Müller, Fabien Cheynis, Stefano Curiotto

Physical Review Letters (2019)

2017

Spatial inhomogeneity and temporal dynamics of a 2D electron gas in interaction with a 2D adatom gas

Fabien Cheynis, Stefano Curiotto, Frédéric Leroy, Pierre Müller

Scientific Reports 7:10642 (2017)10.1038/s41598-017-10300-6

Surface-dependent scenarios for dissolution-driven motion of growing droplets

Stefano Curiotto, Frédéric Leroy, Fabien Cheynis, Pierre Müller

Scientific Reports 7:902 (2017)10.1038/s41598-017-00886-2

Improvement of etching and cleaning methods for integration of raised source and drain in FD-SOI technologies

M. Labrot, F. Cheynis, D. Barge, P. Maury, M. Juhel, S. Lagrasta, Pierre Müller

Microelectronic Engineering 180:56-64 (2017)10.1016/j.mee.2017.04.009

Step density waves on growing vicinal crystal surfaces – Theory and experiment

Bogdan Ranguelov, Pierre Müller, Jean-Jacques Metois, Stoyan Stoyanov

Journal of Crystal Growth 457:184-187 (2017)10.1016/j.jcrysgro.2016.06.041

Dewetting of patterned solid films: Towards a predictive modelling approach

M. Trautmann, F. Cheynis, F. Leroy, S. Curiotto, O. Pierre-Louis, Pierre Müller

Applied Physics Letters 110:263105 (2017)10.1063/1.4990005

Interplay between deoxidation and dewetting for ultrathin SOI films

M. Trautmann, F. Cheynis, F. Leroy, S. Curiotto, Pierre Müller

Applied Physics Letters 110:161601 (2017)10.1063/1.4980132

2016

Low thermal budget for Si and SiGe surface preparation for FD-SOI technology

M. Labrot, F. Cheynis, D. Barge, Pierre Müller, M. Juhel

Applied Surface Science 371:436-446 (2016)10.1016/j.apsusc.2016.02.228

Catalytically enhanced thermal decomposition of chemically grown silicon oxide layers on Si(001)

F. Leroy, T. Passanante, F. Cheynis, S. Curiotto, E. B. Bussmann, Pierre Müller

Applied Physics Letters 108:111601 (2016)10.1063/1.4941799

Elastic cost of silicon step rebonding

F. Leroy, Y. Garreau, F. Cheynis, B. Croset, A. Coati, Pierre Müller, Geoffroy Prévot

Physical Review B: Condensed Matter and Materials Physics 93:045416 (2016)10.1103/PhysRevB.93.045416

How to control solid state dewetting: A short review

F. Leroy, L. Borowik, F. Cheynis, Y. Almadori, S. Curiotto, M. Trautmann, J. C. Barbe, Pierre Müller

Surface Science Reports 71:391-409 (2016)10.1016/j.surfrep.2016.03.002

Step density waves on growing vicinal crystal surfaces – theory and experiment

Bogdan Ranguelov, Pierre Müller, Jean-Jacques Metois, Stoyan Stoyanov

Journal of Crystal Growth (2016)

Financement

Sources et sondes ponctuelles 2

  • ANR grant 2DTransformers (ANR-14-OHRI-0004)

  • ANR grant HoloLEEM (ANR-15-CE09-0012)

  • ANR grant LOTUS (ANR-13-BS04-0004-02)

Collaborations

National

  • O. Pierre-Louis (ILM, Lyon)
  • J. Coraux (Institut Néel, Grenoble)
  • Y. Fagot-Revurat, B. Kierren, D. Malterre (Institut Jean Lamour, Nancy)
  • Salia Cherifi-Hertel (IPCMS, Strasbourg)
  • A. Michon & M. Portail (CHREA, Toulouse)
  • J.-C. Barbé & Ł. Borowik (CEA/LETI, Grenoble)
  • F. Houdelier (CEMES, Toulouse)
  • G. Prévot (INSP, Paris)

 

International

  • B. Ranguelov & M. Michailov (IPC, BAS, Bulgary)
  • Y. Saito (Keio Univ., Japan)
  • C. V. Thompson (MIT, Cambridge, USA)

Brevets

Ł. Borowik, J.-C. Barbé, E. Bussmann, F. Cheynis, F. Leroy, D. Mariolle and P. Müller. Publication Number: US2012282758.

Ł. Borowik, J.-C. Barbé, E. Bussmann, F. Cheynis, F. Leroy, D. Mariolle and P. Müller. Publication Number: US2012282759.

Techniques experimentales

UHV set-up @CINaM

On a daily basis, we work with our Ultra-High Vacuum (UHV) setup dedicated to surface nanoscience that includes a LEEM/PEEM microscope[1,2], a STM/AFM microscope[3,4] and a surface preparation chamber. An overview of the setup is shown below. The LEEM technique allows to record images and movies of a crystalline surface (typical acquisition time 0.1-1s), under a UHV environment (low 10-10 Torr, i.e. around 10-13 bar) or in the presence of a low-partial pressure (low 10-7 Torr) of gas (H2, N2, O2, ...), during heating (≈1300K) or cooling (≈150K).

It is therefore a versatile technique for the in-situ and real-time characterization of surfaces and thin films. LEEM is also powerful as it can record images with nanometric lateral resolution, typically of 5 nanometers, and atomic vertical resolution.
Operated in diffraction mode, Low-Energy Electron Diffraction (LEED) patterns can be obtained to characterize the atomic structure of the sample surface. As in Transmission Electron Microscopy, dark- or bright-field imaging modes are available. Therefore it is possible for instance to distinguish two different terraces of the same crystal separated by an atomic step if they have a different surface structure.

A complete description of the setup can be found in: Rev. Sci. Instr. 85 (2014) 043705

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Examples of LEEM images obtained with our microscope are shown below.
Left: Si(001) surface at 1000°C in dark-field mode. A movie of the sublimation is available here. The black-white contrast arises from the presence of two crystallographic surface structures on adjacent atomically flat terraces (Field-Of-View: 15µm).
Right: Surface of Mo(110) at 1070°C in bright field mode. The step contrast (black lines) is due to the phase shift between scattered waves by two adjacent terraces. The black arrows show a screw dislocation emerging at the surface (left circle) and a circular monoatomic terrace (middle) on top of a mound (Field-Of-View: 7.5µm).

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Nanofabrication PLANETE (CINaM)

Nanoscience routinely requires samples that are artificially structured at the nanometer length scale to unravel unprecedented properties. To do so, we are regular users of the micro- and nanofabrication facility PLANETE (CINaM). More specifically, part of our research rely on clean-room technologies including:

  • Wet chemistry
  • Optical and electronic lithography
  • Reactive Ion Etching

Synchrotron-based techniques

For a complete understanding of the relationship between atomic structure/surface dynamics and electronic properties, complementary characterizations to microscopy are required. Surface-sensitive techniques based on synchrotron radiation provide a unique opportunity to combine real- and reciprocal-space approaches. Here is a short (and non-exhaustive!) list of the setups that we resort to on a regular basis:

  • Grazing Incidence X-ray Diffraction (GIXD) & Grazing Incidence Small Angle X-ray Scattering (GISAXS) @BM32 (ESRF)
  • Angle-Resolved Photo-Emission Spectroscopy (ARPES) @CASSIOPEE (SOLEIL)
  • X-ray Photo-Emission Electron Microscopy (XPEEM) @HERMES (SOLEIL), @Nanospectroscopy (ELETTRA)

Films LEEM

LEEM movies

Electromigration of Au on Ge(111)

2D Au islands (dark grey) detach from step edges and migrate in the direction opposite to the current. Temperature: 500°C. Field of view: 6.5x4.5µm2. Time: 4min. (unpublished results).

 

Electromigration on Si(111)

Electromigration of two single-atom deep holes (dark grey) on a Si(111)-7x7 terrace (light grey). They migrate in the direction opposite to the electric current (that is reversed twice). The holes are in a metastable Si(111)-(1x1) surface reconstruction. Field of view: 28x12µm2. Temperature ≤830°C. Time: 35min (unpublished results).

 

Electromigration on Si(100)

Single-atom deep holes (black ellipses) move under the effect of an electric current. The current direction is from left to right. The sample temperature is at 1170K, the window width is 18µm and the real-time experiment duration is 9 minutes. Appl. Surf. Sci., 469, 463 (2019).

 

2D elec. gas induced by a Ag deposition

At ε=24 eV, the image shows the Ag adatom concentration variations. At ε=1.8 eV, the LEEM image illustrates qualitatively the surface work function time evolution (i.e. the 2DEG doping). Sci. Rep. 7 (2017) 10642.

 

Dewetting of a Si(100) film on a SiO2 substrate

The black-white regions at the top of the imaged area are Si(100) terraces with 2x1 or 1x2 surface reconstruction. The dewetting front advances and when O2 is introduced in the chamber it stops. The Si terraces alternatively blink between white and black during O2 exposure because Si is consumed according to the reaction Si+1/2O2=SiO(gas). The sample temperature is 1100K.

 

Au-Si droplets moving on Si(111)

The droplets climb up and locally dissolve the Si steps (field-of-view: 10µm).

 

Surface phase transformation on Si(111)

White and dark regions are 7x7 and 1x1 surface phases respectively. Below 830ºC the 7x7 phase is stable with a small amount of residual, metastable 1x1. Upon heating the sample above 830ºC, the 7x7 phase reduces and disappears while the 1x1 domains widen. Decreasing the temperature below 830ºC, the 7x7 domains nucleate and grow. The process is reversible. The window width is 7µm.