Surface Science Group
The Surface Science Group, 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 Group, formerly Surface Science Laboratory, has been part of the following organizations at TUT:
- 1999-2010 Surface Science Laboratory, Department of Physics
- 2011-2016 Surface Science Laboratory, Optoelectronics Research Centre
- 2017- Surface Science Group, Photonics Laboratory
- Recent research topics
- Research methods
- Recent publications
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.
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.
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.
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.
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.
Experimentally, the group relies on various surface sensitive methods operating in ultrahigh vacuum. Research equipment includes:
- Spectromicroscopy: Photoemission electron microscopy (PEEM), Small spot spectroscopy XPS/UPS, Energy-filtered imaging XPS/UPS, Chemical mapping, Momentum microscopy in k-space
- Electron spectroscopy: X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), Ultraviolet photoelectron spectroscopy (UPS)
- 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)
- Solar simulator for photonics research
- Optical contact angle meter for measurement of static contact angle, dynamic contact angles, surface free energy, surface tension, interfacial tension, batch contact angle
- Pull-off adhesion gauge
- 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), Near-ambient-pressure X-ray photoelectron spectroscopy (APXPS)
At present, Surface Science Group is engaged in the following projects:
- STEELY: Steely way to sustainable hydrogen economy - Thermally grown oxides on advanced iron alloys for photoelectrochemical hydrogen production by solar water splitting
- FinEstBeaMS: MAX IV Infrastructure - FinEstBeaMS Solid State Materials Research (FIRI project)
- PerforMant: Enhancing performance of artificial photosynthesis by engineered nanomaterials and photon management
- HYBRIDS: Multifunctional thin coatings - Creating innovative and sustainable solutions with multifunctional properties
- 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
- 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)
- Biofunc: Biofunctionalization of stainless steel surfaces using novel electrospray mediated supersonic molecular beam deposition technique
- SR-MAXIV: Synchrotron radiation based studies at MAX IV Laboratory (FIRI project)
For more information of our research contact Prof. Mika Valden.
A. T. Aho, J. Viheriälä, V.-M. Korpijärvi, M. Koskinen, H. Virtanen, K. Lahtonen, J. Saari, M. Valden, and M. Guina, High-power (> 560 mW) 1180 nm DBR laser diode with facets coated by atomic layer deposition, Submitted.
M. Kuzmin, K. Lahtonen, L. Vuori, R. Sánchez-de-Armas, M. Hirsimäki, and M. Valden, Investigation of the structural anisotropy in a self-assembling glycinate layer on Cu(100) by scanning tunneling microscopy and density functional theory calculations, Applied Surface Science, Submitted.
L. Vuori, H. Ali-Löytty, K. Lahtonen, M. Hannula, E. Lehtonen, Y. R. Niu, and M. Valden, Hot dip galvanized steel by nanomolecular silane layers as hybrid interface between zinc and top coatings, Corrosion, In Press. [Abstract]
A. Hiltunen, K. Lahtonen, J. Saari, A. Ojanperä, E. Sarlin, H. Wondraczek, A. Eﬁmov, K. Kaunisto, P. Vivo, C. Maccatok, D. Barreca, P. Fardim, N. Tkachenko, M. Valden, and H. Lemmetyinen, Tailored fabrication of transferable and hollow weblike titanium dioxide structures, ChemPhysChem 18, 64–71 (2017). [Abstract]
L. Reisberg, R. Pärna, A. Kikas, I. Kuusik, V. Kisand, M. Hirsimäki, M. Valden, and E. Nõmmiste, UPS and DFT investigation of the electronic structure of gas-phase trimesic acid, Journal of Electron Spectroscopy and Related Phenomena 213, 11–16 (2016). [Abstract]
H. Ali-Löytty, M. Hannula, M. Honkanen, K. Östman, K. Lahtonen, and M. Valden, Grain orientation dependent Nb–Ti microalloying mediated surface segregation on ferritic stainless steel, Corrosion Science 112, 204–213 (2016). [Abstract]
V. Hynninen, L. Vuori, M. Hannula, K. Tapio, K. Lahtonen, T. Isoniemi, E. Lehtonen, M. Hirsimäki, J. J. Toppari, M. Valden, and V. Hytönen, Improved antifouling properties and selective biofunctionalization of stainless steel by employing heterobifunctional silane-polyethylene glycol overlayers and avidin-biotin technology, Scientific Reports 6, 29324 (2016). [Abstract]
M. Hannula, K. Lahtonen, H. Ali-Löytty, A. A. Zakharov, T. Isotalo, J. Saari, and M. Valden, Fabrication of topographically microstructured titanium silicide interface for advanced photonic applications, Scripta Materialia 119, 76 (2016). [Abstract]
H. Ali-Löytty, M. W. Louie, M. R. Singh, L. Li, H. G. Sanchez Casalongue, H. Ogasawara, E. J. Crumlin, Z. Liu, A. T. Bell, A. Nilsson, and D. Friebel, Ambient-pressure XPS study of a Ni–Fe electrocatalyst for the oxygen evolution reaction, Journal of Physical Chemistry C 120 (4), 2247 (2016). [Abstract]
E. Sariola-Leikas, Z. Ahmed, P. Vivo, A. Ojanperä, K. Lahtonen, J. Saari, M. Valden, H. Lemmetyinen, and A. Efimov, Color bricks: Building highly organized and strongly absorbing multicomponent arrays of terpyridyl perylenes on metal oxide surfaces, Chemistry - A European Journal 22, 1501 (2016). [Abstract]
A. Rantamäki, E. J. Saarinen, J. Lyytikäinen, J. Heikkinen, J. M. Kontio, K. Lahtonen, M. Valden, and O. G. Okhotnikov, Thermal Management in Long-Wavelength Flip-Chip Semiconductor Disk Lasers, IEEE Journal of Selected Topics in Quantum Electronics 21, 1501507 (2015). [Abstract]
A. Rantamäki, E. J. Saarinen, J. Lyytikäinen, J. M. Kontio, J. Heikkinen, K. Lahtonen, M. Valden, and O. G. Okhotnikov, Towards high power flip-chip long-wavelength semiconductor disk lasers, Proceedings of SPIE vol. 9349 (2015). [Abstract]
E. Käpylä, A. Sorkio, S. Teymouri, K. Lahtonen, L. Vuori, M. Valden, H. Skottman, M. Kellomäki, and K. Juuti-Uusitalo, Ormocomp® -modified glass as culture substratum for human embryonic stem cell-derived retinal pigment epithelial cells, Langmuir 30, 14555 (2014). [Abstract]
L. Vuori, M. Hannula, K. Lahtonen, P. Jussila, H. Ali-Löytty, M. Hirsimäki, R. Pärna, E. Nõmmiste, and M. Valden, Controlling the synergetic effects in (3-aminopropyl) trimethoxysilane and (3-mercaptopropyl) trimethoxysilane coadsorption on stainless steel surfaces, Applied Surface Science 317, 856 (2014). [Abstract]
L. Vuori, J. Leppiniemi, M. Hannula, K. Lahtonen, M. Hirsimäki, L. Costelle, E. Nõmmiste, V. Hytönen, and M. Valden, Biofunctional hybrid materials: bimolecular organosilane monolayers on FeCr alloys, Nanotechnology 25, 435603 (2014). [Abstract]
P. S. Heljo, K. Wolff, K. Lahtonen, M. Valden, P. Berger, H. S. Majumdar, and D. Lupo, Anodic oxidation of ultra-thin Ti layers on ITO substrates and their application in organic electronic memory elements, Electrochimica Acta 137, 91 (2014). [Abstract]
B. Augustine, R. Sliz, K. Lahtonen, M. Valden, R. Myllylä, and T. Fabritius, Effect of plasma treated Ag/indium tin oxide anode modification on stability of polymer solar cells, Solar Energy Materials and Solar Cells 128, 330 (2014). [Abstract]
A. Rantamäki, E.J. Saarinen, J. Lyytikäinen, K. Lahtonen, M. Valden, and O.G. Okhotnikov, High power semiconductor disk laser with a semiconductor-dielectric-metal compound mirror, Applied Physics Letters 104, 101110 (2014). [Abstract]