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    Iron-assisted ion beam patterning of Si(001) in the crystalline regime
    (Bristol : IOP, 2012) Macko, S.; Grenzer, J.; Frost, F.; Engler, M.; Hirsch, D.; Fritzsche, M.; Mücklich, A.; Michely, T.
    We present ion beam erosion experiments on Si(001) with simultaneous sputter co-deposition of steel at 660 K. At this temperature, the sample remains within the crystalline regime during ion exposure and pattern formation takes place by phase separation of Si and iron-silicide. After an ion fluence of F ≈ 5.9×10 21 ions m -2, investigations by atomic force microscopy and scanning electron microscopy identify sponge, segmented wall and pillar patterns with high aspect ratios and heights of up to 200 nm. Grazing incidence x-ray diffraction and transmission electron microscopy reveal the structures to be composed of polycrystalline iron-silicide. The observed pattern formation is compared to that in the range of 140-440K under otherwise identical conditions, where a thin amorphous layer forms due to ion bombardment.
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    Key concepts behind forming-free resistive switching incorporated with rectifying transport properties
    (London : Nature Publishing Group, 2013) Shuai, Y.; Ou, X.; Luo, W.; Mücklich, A.; Bürger, D.; Zhou, S.; Wu, C.; Chen, Y.; Zhang, W.; Helm, M.; Mikolajick, T.; Schmidt, O.G.; Schmidt, H.
    This work reports the effect of Ti diffusion on the bipolar resistive switching in Au/BiFeO 3/Pt/Ti capacitor-like structures. Polycrystalline BiFeO 3 thin films are deposited by pulsed laser deposition at different temperatures on Pt/Ti/SiO 2/Si substrates. From the energy filtered transmission electron microscopy and Rutherford backscattering spectrometry it is observed that Ti diffusion occurs if the deposition temperature is above 600 C. The current-voltage (I-V) curves indicate that resistive switching can only be achieved in Au/BiFeO 3/Pt/Ti capacitor-like structures where this Ti diffusion occurs. The effect of Ti diffusion is confirmed by the BiFeO 3 thin films deposited on Pt/sapphire and Pt/Ti/sapphire substrates. The resistive switching needs no electroforming process, and is incorporated with rectifying properties which is potentially useful to suppress the sneak current in a crossbar architecture. Those specific features open a promising alternative concept for nonvolatile memory devices as well as for other memristive devices like synapses in neuromorphic circuits.