Berlin 2012 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 32: Transport Properties I (mainly Spin Physics and Magnetic Fields)
HL 32.9: Talk
Tuesday, March 27, 2012, 12:15–12:30, EW 203
Electrical Spin Injection into Semiconductor Nanowires — •Sebastian Heedt1,3, Isabel Wehrmann1,3, Torsten Rieger1,3, Kamil Sladek1,3, Daniel Bürgler2,3, Detlev Grützmacher1,3, and Thomas Schäpers1,3,4 — 1Peter Grünberg Institut (PGI-9), Forschungszentrum Jülich, 52425 Jülich, Germany — 2Peter Grünberg Institut (PGI-6), Forschungszentrum Jülich, 52425 Jülich, Germany — 3JARA-Fundamentals of Future Information Technology — 4II. Physikalisches Institut, RWTH Aachen, 52056 Aachen, Germany
In order to drive a spin-polarized current into InAs nanowires prepared in a bottom-up approach, ferromagnetic injector and detector electrodes are deposited onto the semiconductor structures. To ensure a well-defined magnetization axis a novel contact preparation process has been conceived employing hydrogen silsesquioxane resist in order to planarize the nanowires. By means of doping and the application of a gate voltage the carrier concentration in the nanowires can be controlled. The spin accumulation is probed in a four terminal non-local measurement geometry. To this end, controlling the interface resistance between the ferromagnet (Co) and the nanowire is of outmost importance. Native indium oxide is removed by in situ Ar+ sputtering. Subsequently an ultra-thin layer of Al2O3 (or MgO respectively) is evaporated in order to overcome the conductivity mismatch between the semiconductor beneath and the ferromagnetic metal above the tunnel barrier. A further unequivocal evidence of spin injection is aspired by measuring the dephasing of the injected spin ensemble in a Hanle setup.