1. Center of Materials Technology and Photonics & Electrical Engineering Department; Technological Educational Institute (TEI) of Crete; Heraklion 71004 Crete Greece
2. Department of Materials Science and Technology; University of Crete; Heraklion 71003 Crete Greece
3. Department of Materials Science and Engineering; University of Ioannina; 45110 Ioannina Greece
4. Physics and Astronomy; Faculty of Physical Sciences and Engineering; University of Southampton; Southampton UK
5. Institute of Electronic Structure and Laser; Foundation for Research and Technology Hellas; P. O. Box 1527 71110 Heraklion Crete Greece