Regensburg 2007 – wissenschaftliches Programm
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SYOE: Symposium Organic Thin Film Electronics: From Molecular Contacts to Devices
SYOE 8: Poster Session SYOE
SYOE 8.98: Poster
Dienstag, 27. März 2007, 18:00–20:00, Poster B
Organic field effect transitors for spin polarised transport - concept and recent advances — •Markus Michelfeit, Jean Geurts, Georg Schmidt, and Laurens W. Molenkamp — Uni Würzburg, Experimentelle Physik III, Am Hubland, 97074 Würzburg
The investigations of spin electronics and organic electronics have been constantly increasing in the last years. Our concept of an organic field-effect transistor (OFET) for spin-polarised transport combines the goals of these two fields of research. Thus the possibility of spin polarised transport would add a new degree of freedom to the conventional charge based transistor. Due to long spin relaxation times (≈ 1µs) organic semiconductors are promising as active materials in such devices. We designed interdigitated source and drain stripe contacts made of CoFeB on a highly doped silicon wafer with a thermally grown SiO2-layer, serving as gate electrode and isolator, respectively. The channel resistance should strongly depend on the state of magnetisation of the source and drain stripes: low resistance for parallel and high resistance for antiparallel magnetisation. For stripe widths of 0.5 and 2 µm, respectively, stable states of parallel or antiparallel magnetisation were achieved by varying the external B-field, exploiting the width-dependence of their coercive field Hc. At 300K SQUID results show Hc = 2.4 and 12 kA/m respectively. The next challenge is the tuning of contact impedance, which is a crucial factor for an ideal spin injection from the ferromagnetic contacts into the organic semiconductor. This work is funded by the DFG Schwerpunktprogramm 1121 on OFETs.