Surface Science Laboratory
The Surface Science Laboratory, led by Prof. Mika Valden, conducts research on the phenomena at surfaces and interfaces of biomaterials, nanostructured materials and semiconductor materials.The main objectives are to gain insights into the physicochemical surface and interface properties at molecular level and to develop novel materials by functionalizing surfaces on the nanometer scale.
The Surface Science Laboratory, previously a part of the Department of Physics, joined ORC at the beginning of 2011.
Contents
Recent research topics
Nanostructured surfaces
Stainless steels (FeCr-based alloys) are versatile materials suitable for many demanding applications. Their functional properties result from processes that take place on the surfaces at molecular level. For instance, the protective oxide layer grows by reaction between oxidizing gases from the environment and various elements from the alloy (Fig. 1). The chemical composition and morphology of surface nanostructures influence many important interactions with other phases or materials, including biomolecules and coatings.
Recently, we have demonstrated that bonding of organofunctional silanes on the alloys [Surf. Interface Anal. 2010] is strongly influenced by surface hydroxylation resulting from water adsorption [Surf. Sci. 2009]. This knowledge has been applied to facilitate metal-polymer adhesion [Appl. Surf. Sci. 2011] and synthesis of biofunctional thin films on stainless steel materials.
>> Read more about nanostructured surfaces
Oxidation at atomic level
The low temperature formation of most metal oxide films follows the Cabrera-Mott model where the film grows as a uniform layer promoted by the electric field induced ionic transport mechanism. Initially, the field-enhanced ionic transport accelerates the oxidation. When the thickness of the oxide film increases, the field is no longer strong enough to cause the ions to migrate and the electric field decreases and the rate of growth attenuates. However, recently it has been found that the Cabrera-Mott -model is not valid for the oxide film formation on copper. It has been shown using electron microscopy that the oxide film grows as Cu2O -islands on a copper surface and not according to the layer-by-layer mode.
In the present work, the oxide films have been prepared on polycrystalline OFHC-copper (Oxygen Free High Conductivity), industrial silver bearing copper (Cu(Ag)), Ag/Cu(100) -model system and on a Cu(100) single crystal under well-defined experimental conditions [J. Chem. Phys. 2007] [J. Chem. Phys. 2008] [J. Chem. Phys. 2008]. The OFHC- and Ag(Cu) copper samples were manufactured by Outokumpu Copper Products Oy. The main objective was to explore the atomic details of the structure sensitivity, oxidation kinetics and surface morphology of the thin oxide film formation on copper and further to make use of this knowledge in the processes used in manufacturing of copper products in collaboration with Outotec Oyj.
>> Read more about oxidation at atomic level
Biofunctionalization of metallic surfaces
Stainless steel (SS) is inherently excellent material choice for applications where the material surface is in contact with biological substances due to the properties of the few nanometre thick passive oxide surface layer. Thus, some SS grades have been successfully used in applications where corrosion resistance and biocompatibility is required. What SS surfaces lack, though, is biofunctionality.
>> Read more about biofunctionalization of metallic surfaces
Reaction dynamics and kinetics at gas-surface interface
The reactivity of a solid state surface is defined by the physicochemical interactions between impinging molecules in the gas phase and the morphology, electronic structure and composition of the surface. A better understanding of these molecular level phenomena would have practical implications, for instance, on the synthesis of coatings, thin films and novel materials with atomic layer epitaxy (ALD) or plasma assisted chemical vapor deposition (PACVD).
Molecular beam surface scattering technique (MBSS) provides the means for probing the microscopic details of elementary surface processes such as adsorption, desorption and surface mediated chemical reactions. In addition to being useful surface sensitive probes, molecular beams can also be used in the synthesis of novel materials. Semiconductor industry, for instance, has long employed molecular beams in the growth of semiconductor materials.
>> Read more about reaction dynamics and kinetics at gas-surface interface
Surface-mediated processes in heterogeneous catalysis
Three-way catalysts contain noble metals such as platinum, palladium and rhodium as the active components (see the figure). One of the recent requirements for catalyst materials is their durability under high temperature conditions. With X-ray Photoelectron Spectroscopy (XPS) it is possible to investigate the chemical composition of the catalyst surfaces, which have an important role in determining the catalytic performance.
The temperature in a close-coupled catalyst converter can rise even above 1000°C, which induces sintering of noble metal clusters and phase transitions of the alumina support. These phenomena, together with irreversible reactions of noble metal and other materials present in the catalyst may lead to a decrease in catalyst conversion capability and increase in pollutant emissions.
>> Read more about surface-mediated processes in heterogeneous catalysis
Research methods
Experimentally, the group relies on various surface sensitive methods operating in ultrahigh vacuum. Research equipment includes:
- Electron spectroscopy: X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), Ultraviolet photoelectron spectroscopy (UPS)
- Spectromicroscopy: Photoemission electron microscopy (PEEM), Small spot spectroscopy XPS/UPS, Energy-filtered imaging XPS/UPS, Momentum microscopy in k-space
- Scanning tunneling microscopy (STM)
- Molecular beam surface scattering (MBSS)
- Low energy electron diffraction (LEED)
- Thermal desorption spectroscopy (TDS)
- Electrochemical instruments: Potentiostat/galvanostat, Electrochemical impedance spectroscopy (EIS), Electrochemical quartz crystal microbalance (EQCM)
- Various sample preparation and surface modification methods in UHV and low pressure: Sputtering, Annealing, Physical vapour deposition (PVD), Activated ion bombardment, Evaporation, Electrospraying, Oxidation, Reduction, Gas exposures, Atomic hydrogen cleaning, etching and passivation, Atomic layer deposition (ALD)
- Various sample preparation and surface modification methods in liquid phase: Electrochemical deposition and treatments, Liquid phase deposition of molecules
- Access to advanced synchrotron radiation-based research facilities at MAX IV Laboratory: High-resolution photoelectron spectroscopy (PES), X-ray absorption spectroscopy (XAS), Photoemission electron microscopy (LEEM, PEEM, XPEEM), High-pressure X-ray photoelectron spectroscopy (HP-XPS)
Electron spectroscopy (XPS, AES, UPS)
Scanning tunneling microscopy (STM)
Molecular beam surface scattering (MBSS)
Low energy electron diffraction (LEED)
Projects
At present, surface science laboratory is engaged in the following projects:
- FABRICS: Fabrication and service performance of advanced stainless steels for demanding exhaust applications
- NanoFinish: Nanostructures and finishing of advanced stainless steel surfaces
- KURKO: Composites for tissue construction
- NANOmat: Modular spectromicroscopy system for nanomaterials synthesis and characterization (FIRI project)
- SR-MAXIV: Synchrotron radiation based studies at MAX IV Laboratory (FIRI project)
- Biofunc: Biofunctionalization of stainless steel surfaces using novel electrospray mediated supersonic molecular beam deposition technique
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Synchrotron radiation mediated research at MAX IV Laboratory (Lund University, Sweden):
- The effect of minor alloying elements on the initial stages of surface oxide formation on FeCr alloys for biomedical applications
- Core-level photoelectron and x-ray absorption spectroscopy of biofunctional layers on advanced metal alloys
- Adsorption geometry and electronic structure of maleimide on silanized FeCr single crystal surface
Recent publications
2013
H. Ali-Löytty, P. Jussila, and M. Valden, Optimization of the electrical properties of Ti–Nb stabilized ferritic stainless steel SOFC interconnect alloy upon high-temperature oxidation: The role of excess Nb on the interfacial oxidation at the oxide–metal interface, International Journal of Hydrogen Energy 38(2), 1039 (2013). [Abstract]
2012
H. Ali-Löytty, P. Jussila, T. Juuti, L.P. Karjalainen, A.A. Zakharov, and M. Valden, Influence of precipitation on initial high-temperature oxidation of Ti-Nb stabilized ferritic stainless steel SOFC interconnect alloy, International Journal of Hydrogen Energy 37(19), 14528 (2012). [Abstract]
I. Aaltio, X.W. Liu, M. Valden, K. Lahtonen, O. Söderberg, Y. Ge, and S.-P. Hannula, Nanoscale surface properties of a Ni-Mn-Ga 10M magnetic shape memory alloy, Journal of Alloys and Compounds, In press. [Abstract]
R. Pärna, U. Joost, E. Nõmmiste, T. Käämbre, A. Kikas, I. Kuusik, I. Kink, M. Hirsimäki, and V. Kisand, Effect of different annealing temperatures and SiO2/Si(100) substrate on the properties of nickel containing titania thin sol-gel films, Physica Status Solidi (a) 209, 953 (2012). [Abstract]
2011
L. Kanninen, N. Jokinen, H. Ali-Löytty, P. Jussila, K. Lahtonen, M. Hirsimäki, M. Kuzmin, R. Pärna, E. Nõmmiste, and M. Valden, Adsorption structure and bonding of trimesic acid on Cu(100), Surface Science 605, 1968-1978 (2011). [Abstract]
K.E. Lilja, H.S. Majumdar, K. Lahtonen, P. Heljo, S. Tuukkanen, T. Joutsenoja, M. Valden, R. Österbacka, and D. Lupo, Effect of dielectric barrier on rectification, injection and transport properties of printed organic diodes, Journal of Physics D: Applied Physics 44, 295301 (2011). [Abstract]
M. Honkanen, M. Hoikkanen, M. Vippola, J. Vuorinen, P. Jussila, H. Ali-Löytty, M. Lampimäki, M. Valden, and T. Lepistö, Characterization of silane layers on modified stainless steel surfaces and related stainless steel-plastic hybrids, Applied Surface Science 257, 9335-9346 (2011). [Abstract]
H. Ali-Löytty, P. Jussila, M. Hirsimäki, and M. Valden, Influence of CrN surface compound on the initial stages of high temperature oxidation of ferritic stainless steel, Applied Surface Science 257, 7783-7791 (2011). [Abstract]
R. Pärna, U. Joost, E. Nõmmiste, T. Käämbre, A. Kikas, I. Kuusik, M. Hirsimäki, I. Kink, and V. Kisand, Effect of cobalt doping and annealing on properties of titania thin films prepared by sol-gel process, Applied Surface Science 257, 6897-6907 (2011). [Abstract]
H. Vuori, A. Pasanen, M. Lindblad, M. Valden, M. Veringa Niemelä, and A.O.I. Krause, The effect of iridium precursor on oxide-supported iridium catalysts prepared by atomic layer deposition, Applied Surface Science 257, 4204-4210 (2011). [Abstract]
2008-2010
R. Pärna, E. Nõmmiste, A. Kikas, P. Jussila, M. Hirsimäki, M. Valden, and V. Kisand, Electron spectroscopic study of passive oxide layer formation on Fe-19Cr-18Ni-1Al-TiC austenitic stainless steel, Journal of Electron Spectroscopy and Related Phenomena 182, 108-114 (2010). [Abstract]
P. Jussila, H. Ali-Löytty, K. Lahtonen, M. Hirsimäki, and M. Valden, Effect of surface hydroxyl concentration on the bonding and morphology of aminopropylsilane thin films on austenitic stainless steel, Surface and Interface Analysis 42, 157-164 (2010). [Abstract]
P. Jussila, H. Ali-Löytty, K. Lahtonen, M. Hirsimäki, and M. Valden, Inhibition of initial surface oxidation by strongly bound hydroxyl species and Cr segregation: H2O and O2 adsorption on Fe-17Cr, Surface Science 603, 3005-3010 (2009). [Abstract]
K. Lahtonen, M. Lampimäki, M. Hirsimäki, and M. Valden, Kinetic hindrance during the surface oxidation of Cu(100)-c(10x2)-Ag, Journal of Chemical Physics 129, 194707 (2008). [Abstract]
K. Lahtonen, M. Hirsimäki, M. Lampimäki, and M. Valden, Oxygen adsorption-induced nanostructures and island formation on Cu{100}: Bridging the gap between the formation of surface confined oxygen chemisorption layer and oxide formation, Journal of Chemical Physics 129, 124703 (2008). [Open Access]
M. Ahonen, M. Hirsimäki, A. Puisto, S. Auvinen, M. Valden, and M. Alatalo, Adsorption dynamics of O2 on Cu(100): the role of vacancies, steps and adatoms in dissociative chemisorption of O2, Chemical Physics Letters 456, 211-214 (2008). [Abstract]
P. Jussila, K. Lahtonen, M. Lampimäki, M. Hirsimäki, and M. Valden, Influence of minor alloying elements on the initial stages of oxidation of austenitic stainless steel materials, Surface and Interface Analysis 40, 1149-1156 (2008). [Abstract]
P. Jussila, K. Lahtonen, M. Lampimäki, M. Hirsimäki, M. Honkanen, T. Lepistö, P. Taskinen, and M. Valden, Ag/Cu(100) surface alloy and polycrystalline Cu(Ag) alloy studied by XPS, Surface Science Spectra 15, 31-40 (2008). [Abstract]
V. Kisand, A. Kikas, E. Kukk, E. Nõmmiste, K. Kooser, T. Käämbre, R. Ruus, M. Valden, M. Hirsimäki, P. Jussila, M. Lampimäki, H. Aksela, and S. Aksela, Substrate-induced effects in the creation and decay of potassium 2p core excitations in ultrathin films of KCl on copper, Journal of Physics: Condensed matter 20, 145206 (2008). [Abstract]
>> Complete list of publications and theses
Contact
For more information of our research contact Prof. Mika Valden.