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
- Main research areas
- Research methods
- Recent publications
Nanostructured materials are indispensable for many applications, especially for production of photonic devices. Their functional properties can be easily modified by controlling the structure of the material on the surface, which strongly affects the interaction of light with the material. The chemical composition and morphology of surface nanostructures influence many important interactions with other phases or materials, allowing applications in photoelectrochemistry.
Fig.1: SEM image of TiSi microstructure on Si, compositional contrast
Recently, we have demonstrated that microstructured TiSi films (Fig.1) form during annealing of TiO2 ALD films on Si [Scr. Mat. 2016]. This knowledge allows for creation of a scalable process for augmenting TiSi heterostructures for photovoltaic and photoelectrochemical applications and shines light on role of TiO2 reduction and Si diffusion in formation of such films.
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.
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
- 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)
- HYBRIDS: Multifunctional thin coatings - Creating innovative and sustainable solutions with multifunctional properties
For more information of our research contact Prof. Mika Valden.
M. Hannula, H. Ali-Löytty, K. Lahtonen, E. Sarlin, J. Saari, and M. Valden, Improved stability of ALD grown amorphous TiO2 photoelectrode coatings by thermally induced oxygen defects, Submitted to Chemistry of Materials.
M. Kanerva, S. Korkiakoski, K. Lahtonen, E. Sarlin, S. Palola, A. Iyer, L. Xuwen, S. Tervakangas, and M. Valden, DLC-treated aramid-fibre composites: improvements by nanoscale-coated reinforcement, Submitted to Composites Science and Technology.
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.
R. Pärna, R. Sankari, E. Kukk, E. Nõmmiste, M. Valden, M. Lastusaari, K. Kooser, K. Kokko, M. Hirsimäki, S. Urpelainen, P. Turunen, A. Kivimäki, V. Pankratov, L. Reisberg, F. Hennies, H. Tarawneh, R. Nyholm, and M. Huttula, FinEstBeaMS - a Wide-range Finnish-Estonian Beamline for Materials Science at the 1.5 GeV Storage Ring at the MAX IV Laboratory, Nuclear Instruments and Methods in Physics Research A: Accelerators, Spectrometers, Detectors and Associated Equipment 859, 83–89 (2017). [Abstract]
L. George, E. Efimova, E. Sariola-Leikas, K. Lahtonen, M. Valden, P. Vivo, H. Hakola, A. Hiltunen, and A. Eﬁmov, Building up colors: multilayered arrays of peryleneimides on flat surfaces and on mesoporous layers, ChemPlusChem 82, 1–12 (2017). [Abstract]
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 409, 111–116 (2017). [Abstract]
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 73(2), 169–180 (2017). [Abstract]
A. Hiltunen, K. Lahtonen, J. Saari, A. Ojanperä, E. Sarlin, H. Wondraczek, A. Eﬁmov, K. Kaunisto, P. Vivo, C. Maccato, 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]