Pekka Laukkanen
Understanding and processing the properties of surface and interface parts of solid semiconductor crystals (e.g., Si, Ge, GaAs, GaInAs, InSb, InP) on atomic scale have become more and more essential to develop energy-efficient devices with new functionalities in various fields such as electronics and photonics. The surface and interface layers form such a crucial part of nanoscale functional semiconductor materials, including nanocrystals and –wires as well as nanometer thick semiconductor films.
 
It is however challenging to investigate and process the properties of these surfaces and interfaces on atomic scale because semiconductor crystals often interact strongly with their environment (e.g., semiconductor surfaces become easily oxidized in air) and because it is difficult to probe the properties of thin and buried interface layers.
 
To contribute significantly to obtaining solutions to the above scientific and technological problems, our group has set the following objectives. In this experimental research, our targets are (i) to synthesize and characterize novel thin films on semiconductor crystals and (ii) to transfer the result to device tests.
 
The synthesized films like oxide layers are novel because they are crystalline. These crystalline films are potential parts to passivate semiconductor crystals and to construct the device interface stacks (junctions) of semiconductors because crystalline materials naturally include less defects harmful to device functionalities, as compared to amorphous films or interfaces. Last but not least, crystalline films on semiconductor crystals provide a well-defined platform (model system) to elucidate the materials properties in detail.
 
The thin-film synthesis is mainly performed with ultrahigh-vacuum based equipments at the Department of Physics and Astronomy. The characterization methods include electron diffraction, scanning-tunneling microscopy, x-ray photoelectron spectroscopy at the Department of Physics and Astronomy as well as state-of-the-art synchrotron-radiation facilities at MAX-lab in Lund. Via collaboration, the synthesized films are tested as a part of capacitors for example.
 

Selected publications related to the work:

  • J. J. K. Lång, M. P. J. Punkkinen, M. Tuominen, H.-P. Hedman, M. Vähä-Heikkilä, V. Polojärvi, J. Salmi, V.-M. Korpijärvi, K. Schulte, M. Kuzmin, R. Punkkinen, P. Laukkanen, M. Guina, and K. Kokko: Unveiling and controlling the electronic structure of oxidized semiconductor surfaces: crystalline oxidized InSb(100)(1×2)-O. Physical Review B, Vol. 90 (2014) 045312.
  • A. Aho, V. Polojärvi, V.-M. Korpijärvi, J. Salmi, A. Tukiainen, J. Tommila, P. Laukkanen, and M. Guina: Composition Dependent Growth Dynamics of MBE-Grown GaInNAs Solar Cells. Solar Energy Materials and Solar Cells, Vol. 124 (2014) 150.
  • P. Laukkanen, J.J.K. Lång, M.P.J. Punkkinen, M. Tuominen, J. Dahl, V. Tuominen, K. Kokko, M. Kuzmin, V. Polojärvi, J. Salmi, V.-M. Korpijärvi, A. Aho, A. Tukiainen, M. Guina, H.-P. Hedman, and R. Punkkinen: Synthesis and Characterization of Layered Tin Monoxide Thin Films with Monocrystalline Structure on III-V Compound Semiconductor. Advanced Materials: Interfaces, Vol. 1 (2014) issue 2.
  • M. Yasir, J. Dahl, M. Kuzmin, J. Lång, M. Tuominen, M. P. J. Punkkinen, P. Laukkanen, K. Kokko, V.-M. Korpijärvi, V. Polojärvi, and M. Guina: Growth and properties of crystalline barium oxide on the GaAs(100) substrate. Applied Physics Letters, Vol. 103 (2013) 191601.
  • M.P.J. Punkkinen, P. Laukkanen, J. Lång, M. Kuzmin, M. Tuominen, V. Tuominen, J. Dahl, M. Pessa, M. Guina, K. Kokko, J. Sadowski, B. Johansson, I.J. Väyrynen, and L. Vitos: Ordered oxide films and semiconductor-oxide interfaces for high performance semiconductor devices. Physical Review B, Vol. 83 (2011) 195329.

Contact information

Department of Physics and Astronomy
Tel: +358-(0)2-333-6659
E-mail: pekka.laukkanen [at] utu.fi

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