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Group Facilities

Experimental Cluster for Surface and Interface Science

MBE

The Cluster represents one of the most complex such systems in Europe, makes possible the

preparation and characterization in situ of surfaces and interfaces, and consists of three mutually coupled units:

- The MBE (Molecular Beam Epitaxy) Chamber;

- The STM (Scanning Tunneling Microscope) Chamber;

- The Spin- and Angle-resolved Photoelectron Spectroscopy (SARPES).

All chambers operate in ultrahigh vacuum (UHV), the base pressure ranges from 1-2 x 10-10 mbar to 10-11 mbar range The overall value of the whole system exceeds 1.3 M€. The employed techniques are:

In the MBE chamber: a) preparation facilities:

- sample heating up to 1200 C; cooling down to 77 K;

- evaporation from a 4-target e-beam evaporator;

- evaporation from a high temperature Knudsen cell (2000 C);

- controlled gas adsorption and desorption;

- monitor of thicknesses using a quartz microbalance.

b) in situ characterization: - LEED (Low Energy Electron Diffraction);

- RHEED (Reflection High Energy Electron Spectroscopy);

- AES (Auger Electron Spectroscopy);

- Quadrupole Mass Spectroscopy (thermal induced desorption, photodesorption);

 

In the STM chamber:

- sample preparation stage (heating, ion sputtering);

- tip preparation (ion sputtering);

- variable temperature (77 - 453 K) scanning tunneling microscopy (STM);

- scanning tunneling spectroscopy (STS);

In the SARPES chamber:

- conventional X-ray photoelectron spectroscopy using a dual (Al/Mg Kα) anode;

- high resolution XPS using a monochromatized dual (Al Kα /Ag Lα) source;

- ultraviolet photoelectron spectroscopy (UPS);

- angle-resolved XPS: x-ray photoelectron diffraction (XPD);

- angle-resolved UPS (ARUPS): band structure, Fermi surface, etc.;

- spin-resolved UPS: spin-polarized density of states;

- angle- and spin-resolved UPS: spin-polarized band structure;

- programable ion sputtering: depth profiling;

- flood gun for sample neutralization;

- electron gun for AES;

- medium energy ion scattering spectroscopy (MEIS).

In approximately 18 months of operation of the surface and interface facility, a significant number of scientific papers resulted, published in ISI ranked journals:

1. Mesoporous Tin-Triflate Based Catalysts for Transesterification of Sunflower Oil, M. Verziu, J. El Haskouri, D. Beltran, P. Amoros, D. Macovei, N.G. Gheorghe, C.M. Teodorescu, S.M. Coman, V. I. Parvulescu, Top. Catal. 53, 763-772 (2010).

2. Chemical Imaging of Catalyst Deactivation during Biomass Conversion Processes: The Etherification of Biomass-based Alcohols with Alkenes over H-Beta Zeolites, A.N. Parvulescu, D.Mores, E. Stavitski, C.M. Teodorescu, P.C.A. Bruijnincx, R.J.M. Klein Gebbink and B.M. Weckhuysen, J. Amer. Chem. Soc. 132, 10429-10439 (2010).

3. Thermodynamic destabilization of Li-N-H system by Si addition, P. Palade, G.A. Lungu, A.M. Husanu, J. Alloys Compds. 505, 343-347 (2010).

4. One-Pot Synthesis of Menthol Catalyzed by a Highly Diastereoselective Ionic Gold/MgF2 Catalyst, A. Negoi, S. Wuttke, E. Kemnitz, D. Macovei, C. M. Teodorescu, V.I. Parvulescu, S.M. Coman, Angew. Chem. Intl. Ed. 49, 8134-8138 (2010).

5. Novel Pd heterogeneous catalysts for cycloisomerisation of acetylenic carboxylic acids, F. Neatu, L. Protesescu, M. Florea, V.I. Parvulescu, C.M. Teodorescu, N. Apostol, P.Y. Toullec, V. Michelet, Green Chemistry 12, 2145-2149 (2010).

6. Structural investigations of Ge nanoparticles embedded in an amorphous SiO2 matrix, I. Stavarache, A.M. Lepadatu, N.G. Gheorghe, R.M. Costescu, G. Stan, D. Marcov, A. Slav, G. Iordache, T.F. Stoica, V. Iancu, V.S. Teodorescu, C.M. Teodorescu, M.L. Ciurea, J. Nanopart. Res.13, 221-232 (2010).

7. Preparation and characterization of iron oxides embedded in fullerite matrices, G.A. Lungu, D. Macovei, C.M. Teodorescu, Digest J. Nanomater. Biostr. 5, 85-95 (2010).

8. Nanostructured thin layers of vanadium oxides doped with cobalt, prepared by pulsed laser ablation: chemistry, local atomic structure, morphology, and magnetism, C.M. Teodorescu , G. Socol, C. Negrila, D. Luca, D. Macovei, J. Exper. Nanosci. 5, 509-526 (2010).

9. Cobalt doped ZnO prepared by electrochemistry: chemistry, morphology, and magnetism, I. Enculescu, E. Matei, V. Vasilache, C.M. Teodorescu, phys. stat. sol. (a) 207 , 2517-2522 (2010).

10. Analysis of electron traps at the 4H-SiC/SiO2 interface; influence by nitrogen implantation prior to wet oxidation, I. Pintilie, C. M. Teodorescu, F. Moscatelli, R. Nipoti, A. Poggi, S. Solmi, L. S. Lvlie and B. G. Svensson, J. Appl. Phys. 108, 024503 (2010).

11. New analytical approximation of diffraction size broadened peak profile for spherical crystallites with lognormal distribution, N.C. Popa, C.M. Teodorescu, S. Frunza, J. Appl. Cryst. 43, 1027-1030 (2010).

12. Atomic structure and magnetic properties of cobalt doped ZnO thin films prepared by sol-gel method, J. Neamtu, G. Georgescu, T. Malaeru, N.G. Gheorghe, R.M. Costescu, I. Jitaru, J. Ferr, D. Macovei, C.M. Teodorescu, Digest J. Nanomater. Biostr. 5, 873-885 (2010).

13. Dielectric and Ferroelectric Characterization of Ba0,95Tm0,05TiO3 Ceramics Derived from Sol-Gel, Marin Cernea, Bogdan S. Vasile, Paul Ganea, Roxana Radu, Valentina Mihalache, Adrian Husanu, Journal of the American Ceramic Society, accepted. (2010) DOI: 10.1111/j.1551-2916.2010.04179.x

14. Polymer-like and diamond-like carbon coatings prepared by RF-PECVD for biomedical applications, G.E. Stan, D.A. Marcov, A.C. Popa, M.A. Husanu, Dig. J. Nanomater. Biostruct. 5, 705–718 (2010).

15. Biocatalytic microreactor incorporating HRP anchored on micro-/nano-lithographic patterns for flow oxidation of phenols, M. Tudorache, D. Mahalu, C. Teodorescu, R. Stan, C. Bala, V.I. Parvulescu, J. Molec. Catal. B: Enzym. 69, 133-139 (2011).

16. Enhanced contamination of Si(001) when analyzed with AES with respect to XPS, N.G. Gheorghe, G.A. Lungu, R.M. Costescu, D.G. Popescu, C.M. Teodorescu, Dig. J. Nanomater. Biostruct. 6 (2), p. 508-513 (2011).

17. Telomerization of 1,3-Butadiene with Biomass-Derived Alcohols over a Heterogeneous Pd/TPPTS Catalyst Based on Layered Double Hydroxides, A.N. Parvulescu, P.J.C. Hausoul, P.C.A. Bruijnincx, S.T. Korhonen, C. Teodorescu, R.J.M.K. Gebbink, B.M. Weckhuysen, ACS Catalysis 1(5), p. 526-536 (2011).

16. X-ray Absorption Fine Structure Investigations on Heat-Treated Cr-doped Titania Thin Films, D. Mardare, V. Nica, V. Pohoata, Dan Macovei, N. Gheorghe, D. Luca, C.M. Teodorescu, Thin Solid Films, in press (2010).

17. Substrate-target distance dependence of structural and optical properties in case of Pb(Zr,Ti)O3 films obtained by Pulsed Laser Deposition, A.C. Galca, V. Stancu, M. A. Husanu, C. Dragoi, N.G. Gheorghe, L. Trupina, M. Enculescu, E. Vasile, Appl. Surf Sci. 257, 5938-5943 (2011).

18. Significantly different contamination of atomically clean Si(001) when investigated by XPS and AES, N.G. Gheorghe, G.A. Lungu, R.M. Costescu, C.M. Teodorescu, phys. stat. sol. (b), accepted (2011).

19. Reactivity, magnetism and local atomic structure in ferromagnetic Fe layers deposited on Si(001), N.G. Gheorghe, M.A. Husanu, G.A. Lungu, R.M. Costescu, D. Macovei, C.M. Teodorescu, Solid State Sciences., submitted (2011).

20. Epitaxial ferromagnetic SmSi synthesized on Si(001), N.G. Gheorghe, R.M. Costescu, M.A. Husanu, G.A. Lungu, D. Macovei, I. Pintilie, D.G. Popescu, C.M. Teodorescu, Phys. Rev. B., correct version submitted (2011).

21. Highly adherent bioactive glass thin films synthetized by magnetron sputtering at low temperature, G.E. Stan, I. Pasuk, M.A. Husanu, I. Enculescu, S. Pina, A.F. Lemos, D.U. Tulyaganov, K. El Mabrouk, J.M.F. Ferreira, Acta Biomaterialia, submitted (2011).

Furthermore, these systems have made it possible to initiate the CNCSIS-PCCE Project Surface and Interface Science: Physics, Chemistry, Biology, Applications (ID_76, funding about € 1.7 Million) in satisfactory conditions as well as win two IFA-CEA cooperation contracts in 2010 and to apply for a new French-Romanian Joint Project in 2011.

Contact person: Dr. Cristian-Mihail Teodorescu  ...e-mail...

Ntegra Aura Scanning Probe Microscopy (SPM) Station

STM1

Available techniques:

1. Atomic Force Microscopy (AFM) with:

− (Contact mode) Force modulation technique. Topography and local elasticity images.

− (Contact mode) Contact Capacitance Technique. Topography and local capacitance images.

− (Contact mode) Lateral force imaging.

− (Contact mode) Piezo Force Microscopy.

− (Contact mode) Spreading resistance imaging.

− (Semicontact mode) Phase contrast imaging.

− Lithography operations. Two ways for lithography impact (BV/SP). Two ways for lithography execution (Raster/Vector).

− Heating stage operations.

− Operations in liquid.

2. Double-pass techniques: − Magnetic Force Microscopy (MFM).

− Electrostatic Force Microscopy (EFM).

− Scanning Kelvin Microscopy (SKM).

− Scanning Capacitance Microscopy (SCM).

3. Scanning Tunneling Microscopy (STM) mode.

4. Nanoindentation.

Contact person: Dr. Cristian-Mihail Teodorescu  ...e-mail...

MULTIMETHOD SURFACE ANALYSIS SYSTEM FOR XPS, AES AND STM

XPS1

CHARACTERIZATION METHODS

 

X-ray Photoelectron Spectroscopy (XPS) - a spectroscopic technique based on photoelectric effect that measures the elemental composition, valence state and electronic state of the elements that exit within a material

 

Auger Electron Spectroscopy (AES) - an analytical technique based on Auger effect used for chemical characterization of surfaces and bulk materials

 

Scanning Tunneling Microscopy (STM) - a characterization technique based on quantum tunneling effect used for surface imaging at atomic resolution

EXPECTABLE OBTAINED DATA FROM XPS, AES and STM MEASUREMENTS

Elements and the quantity of those elements that are present within ~10 nm from the sample surface

Contamination from the surface or the bulk of the sample

Empirical formula of materials

Chemical state identification of elements (valence state, oxidation state)

Binding energy (BE) of electronic states

Thickness of thin layers (1–8 nm) of different materials on the surface

Density of electronic states

Depth compositional profile

Surfaces morphology at the atomic level

 

PERFORMANCES

Detects all chemical elements except hydrogen and helium

Detection limits for most of the elements are in the parts per thousand range (1-3 )

High surface sensitivity since the electrons come from the first 10-20 layers of the surface

High surface imaging resolution in STM technique: 0.2

Nondestructive analysis of materials: metals, alloys, ceramics and most glasses are not

measurably degraded by X-rays. Polymers, catalysts, certain highly oxygenated

compounds, various inorganic compounds and fine organics are low degraded by either

monochromatic or non-monochromatic X-ray sources.

 

APPLICATIONS

Materials and surfaces science

Microelectronics

Etching and corrosion processes (oxidation states of elements, chemical changes in surface

composition, depth profiling)

Heterogeneous catalysis (chemical species identification, chemical states of active species,

chemical changes during reaction)

Ascertainment of: the elemental composition, the chemical and electronic state of the

elements existing on surface, the atomic composition on surface

Control of the concentration of heavy metals or of the other pollutants in sediments and soil

Contact person: Dr. Cristian-Mihail Teodorescu  ...e-mail...

The PEEM (Photoemission Electron Microscopy) and LEEM (Low Energy Electron Microscopy) system.

LEEM_PEEM

The setup operates in ultrahigh vacuum (below 2 x 10-10 mbar).

Methods available:

- Low energy electron microscopy (LEEM) in bright and dark field with a lateral resolution of 4 nm;

- Photoemission electron microscopy (PEEM) with two UV excitation sources (Hg lamp and He I - He II lamp), lateral resolution about 15 nm;

- Mirror electron microscopy (MEM);

- Micro-Low energy electron diffraction (Micro-LEED);

- k-space mapping with sub-micron lateral resolution (individual grains).

- recording LEEM, PEEM, MEM, LEED movies in real time during thermal treatments, ion sputtering or thin layer growth.

Contact person: Dr. Cristian-Mihail Teodorescu  ...e-mail...

Updated: 31 ian 2012 - Ionel Stavarache: stavarache@infim.ro