Berlin 2018 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 29: Focussed Session: Metasurfaces I

HL 29.8: Vortrag

Mittwoch, 14. März 2018, 18:15–18:30, EW 201

Sub-wavelength phase coexistence patterning of phase change materials by means of ion irradiation — •Martin Hafermann, Jura Rensberg, and Carsten Ronning — Institute of Solid State Physics, Friedrich Schiller University Jena, Max-Wien-Platz 1, 07743 Jena, Germany

Phase change materials such as the chalcogenide GeSb_xTe_y (GST) enable the fabrication of reconfigurable devices like rewritable optical data storage media. In such devices switching between two states (amorphous - crystalline) is usually accomplished by applying intense laser pulses. The two states show a tremendous difference of the optical and electrical properties. Using direct laser writing GST based metasurfaces were created by structuring regular patterns of amorphous GST within the crystalline film or vice versa. However, the size of any pattern element is diffraction limited and cannot be smaller than the wavelength of laser light used. To circumvent the diffraction limit, instead of a laser we use a focused ion beam. The ion irradiation induced defect formation triggers the phase transition from crystalline to amorphous in predefined regions, which enables the patterning of GST films down to structure sizes much smaller than the wavelength of visible light. Here, we demonstrate the influence of homogenous ion irradiation on the optical properties of GST thin films. These results were used to design and fabricate sub-wavelength patterns of irradiated GST using area-selective ion irradiation. With this method we are able to create reconfigurable, inherently flat metasurfaces, which is a main desire of modern optics.