ANM
2010
3rd
International Conference on Advanced Nano Materials
12-15 September 2010 - Agadir, Morocco
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Abstract
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ANMM113 |
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BIOMIMETIC INERTIAL SENSOR BASED ON NANOWIRES AND MAGNETORESISTANCE |
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H. Brueckl(1), P. Schroeder(1), T. Burchhart(2) and A. Lugstein(2) |
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(1) AIT Austrian Institute of Technology, Nano Systems, Vienna, Austria
(2) Vienna University of Technology, Institute for Solid State Electronics, Vienna, Austria |
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Crickets,
and other orthopteroidea, possess one of the most sensitive hair-based
sensory systems found in nature. Tiny hairs on the backward Cerci feel
slightest air movements of only 0.1 m/hour velocity. We try to mimic
this concept in an artificial sensor combining nanowires and magnetic
detection. The intention of the collaborative project is to integrate
self-assembled nanowires containing magnetic components in thin film
sensors exhibiting giant magnetoresistive (GMR) effects. Any movement
of the nanowires is translated to the adherent magnetic components and
can be detected via their stray fields by the adjacent GMR stack. The
proposed sensor is very simple, and hence low-cost and competitive.
Vertical Ge and Si nanowires are grown by Vapor-Liquid-Solid (VLS)-CVD
method. The diameters are typically around 100 nm and can be controlled
by adjusting the Au seed sizes. Resonance frequencies of kHz to MHz
depend on the nanowires lengths. We developed a low temperature process
for Ge nanowires at moderate 310°C which enables the direct growth
on a GMR film while the magnetoresistive signal amplitude show only a
slight degradation (decrease to an acceptable value of 9%). The GMR
stack comprises MgO 4nm/ CoFe 2nm/ (Cu 2,4nm/ NiFe 3nm) x10/ Ta 2nm and
shows a high sensitivity of 1,5mΩ/Oe at a total magnetoresistance
amplitude of 12%. A critical issue is the implementation of suitable
magnetic components to the nanowires. Chemical fixation of
functionalized magnetic nanoparticles on the topmost Au seeds by
mercaptan binding appears not to be selective and reliable enough.
However, a lithographic process seems to be applicable if all
self-organized approaches would not. Resist covered Si nanowires are
etched in oxygen plasma until only their tips are visible. The latter
are cladded after deposition of ferromagnetic material and a successive
lift-off process.
This project is funded by the Austrian Science Fund (FWF, # L332-N16).
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