1. School of Physics and Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN), Trinity College Dublin, Dublin 2, Ireland
2. Institute of Solid State Physics, Russian Academy of Sciences, Chernogolovka, Russia
3. School of Physical Sciences, Dublin City University, Dublin 9, Ireland
4. Institute of Microelectronics Technology and High Purity Materials, Russian Academy of Sciences, Chernogolovka, Russia
5. AMBER, the SFI Research Centre for Advanced Materials and BioEngineering Research, Dublin 2, Ireland