Aix-Marseille Univ. collaborations

• O. M. Texier & O. Thomas (IM2NP, Marseille)
• C. Martin (PIIM, Marseille)

French Collaborations

• • O. Pierre-Louis (ILM, Lyon)
  • E. Bernard (CEA/IRFM, Saint Paul-lez-Durance)
  • S. Cherifi-Hertel (IPCMS, Strasbourg)
  • Y. Fagot-Revurat, B. Kierren & D. Malterre (Institut Jean Lamour, Nancy)
  • A. Michon, M. Al Khalfioui  & M. Portail (CRHEA, Valbonne)
  • J.-P. Attané & L. Vila (CEA/SPINTEC, Grenoble)
  • J. Coraux (Institut Néel, Grenoble)
  • L. Martinelli & G. Renaud (ESRF, beamline BM32, Grenoble)

International collaborations

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

• Method for making semi-conductor nanocrystals (Nov. 8, 2012)

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

• Method for making semi-conductor nanocrystals oriented along a predefined direction (Nov. 8, 2012)

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

UHV set-up @ CINaM

On a daily basis, we use a UHV experimental set dedicated to surface physics, including a LEEM/PEEM microscope ^[1,2], a STM/AFM microscope ^[3,4] and a surface preparation chamber. An overview of the equipment can be seen below. The LEEM microscopy technique enables us to visualize and film crystalline surfaces (typical acquisition time 0.1-1s) in a UHV environment (a few 10^-10 Torr or typ. 10^-13 bar) or under a partial pressure (a few 10^-7 Torr : H₂, N_2, O₂, ...) at high temperatures (≈1300K)or below room temperature (≈150K).

this technique is therefore particularly well suited to in-situ, real-time characterization of crystalline surfaces and thin films on a mesoscopic scale (field of view: a few 1µm to 50µm with a typical lateral resolution of 5nm and a vertical atomic resolution).
In diffraction mode, this equipment can acquire LEED (Low-Energy Electron Diffraction) images, enabling to determine the atomic structure of the imaged surface. As with transmission electron microscopy (TEM), LEEM microscopy enables both bright-field and dark-field imaging of the surface to be characterized. This makes it possible to distinguish regions with different atomic arrangements on the surface.

A full description of the instrumental set-up can be found in the following reference: Rev. Sci. Instr. 85 (2014) 043705

Examples of LEEM images obtained with our microscope are available below.
Left: Si(001) surface at 1000°C in dark field. The white-black contrast results from the difference in crystallographic structure between adjacent atomic terraces in the case of Si(001) (field of view: 15µm). A film illustrating the sublimation of the silicon surface at high temperatures is also available here.
Right: Mo(110) surface at 1070°C in bright-field mode. The contrast used to visualize atomic steps (black lines) is due to the phase difference between electron waves scattered by two terraces separating a step. The black circle indicates a screw dislocation emerging from the crystal surface, and the black arrow indicates a circular atomic step at the top of a circular pyramid (field of view: 7.5µm).

Nanofabrication @PLANETE (CINaM)

Nanoscience research frequently relies on the use of artificially structured samples on the nanometric scale. For this reason, we are regular users of the nanofabrication platform PLANETE at CINaM. More specifically, our scientific projects require the use of clean-room technology processes such as :

• Chemical cleaning
• Optical and/or electronic lithography
• Plasma etching

Characterization techniques and Synchrotron facilities

For a detailed understanding of the relationships between atomic structure, surface dynamics and electronic properties, characterizations complementary to those available in our experimental set are generally required. Surface characterization techniques based on synchrotron radiation offer the possibility of combining real-space and reciprocal-space approaches. Here is a short (and non-exhaustive!) list of the techniques we regularly use:

• Grazing Incidence X-ray diffraction (GIXD) & Grazing Incidence Small-Angles X-ray scattering (GISAXS) @BM32 (ESRF)
• Angle-resolved photoemission spectroscopy (ARPES) @CASSIOPEE (SOLEIL)
• Spectromicroscopy XPEEM @HERMES (SOLEIL), @Nanospectroscopy (ELETTRA)

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.