Berlin 2008 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 9: ZnO: Preparation and characterization I
HL 9.2: Vortrag
Montag, 25. Februar 2008, 15:15–15:30, EW 201
ZnO-nanowire as a nanogenerator? — •Markus Andreas Schubert, Stephan Senz, Marin Alexe, and Ulrich Gösele — Max Planck Institut für Mikrostrukturphysik, Weinberg 2, 06120 Halle
Recently nanogenerators for powering nanodevices were reported [1] in which ZnO-nanowire arrays convert mechanical energy in electrical energy by bending the ZnO-nanowires.
We simulate the experiments in which the ZnO nanowires were bent by AFM tip [2] by FEM-calculations for an ideal nonconducting piezoelectric ZnO-nanowire with a length of 600 nm and a diameter of 50 nm fixed perpendicular to a substrate. The top part of this nanowire was bent about 140 nm by a force applied at the top of the nanowire. At the point of the applied force the electrical potential has a maximum of +1.3 V. In the rest of the nanowire the electrical potential is +0.3 V for the stretched side and -0.3 V for the compressed. The piezoelectric charge generate the signal on the capacitance between the two sides, which is about 10−5 pF for the whole wire. A lower value of 10−7 pF is estimated for the AFM point contact.
However, most ZnO-nanowires are n-doped semiconductors with a typically resistivity of 1 Ωcm. One consequence is a very fast discharging of the piezoelectric generate charge in the order of magnitude of 1 ps. Even, in the case of an ideal nonconducting nanowire, the voltage at the input capacity of any preamplifier (∼1-5 pF) would be of the order of 10−7 V, which corresponds to a charge of about one electron.
[1] Y. Gao and Z.L. Wang, Nano Letters 7, 2499–2505 (2007)
[2] Z.L. Wang and J. Song, Science 312, 242–246 (2006)