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| - MEMS/NEMS |
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| - Nanometrology |
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| - Nanofabrication |
| Nanometrology for Nanomaterials using Integrated Nanoprobes |
| Motivation |
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We are developing nano-tools for nanometrology.
Multi-probe systems for scanning probe microscopy (SPM)
have been developed for electrical property measurement of nanomaterials,
such as semiconductor nano-wire, few-layer graphene and nanocarbons.
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| Originality |
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A Pt electrode split by nanogap (50 nm) was integrated on a Si cantilever for SPM.
In-plain resistance (conductance) of nanomaterials can be measured without any lithographic processes.
A conductance image of few-layer graphene on SiC was successfully obtained for the first time.
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| Impact |
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Nanotools based on SPM technology will be powerful tools for the development of nanomaterials.
Various types of the nanotools will be realized in the near future. Next-generation materials for future electron devices
will be discovered by employing such the nanotools.
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| Recent Activities |
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Contact Conductance Measurement of Locally Suspended Graphene on SiC M. Nagase, H. Hibino, H. Kageshima, and H. Yamaguchi, Applied Physics Express 3 (2010) 045101 |
| The characteristics of suspended graphene membran structures formed by partial etching underneath SiC were revealed by using atomic force microscopy. The contact force dependence of topographic and electrical conductance images were measured with a metal (Rh) coated microprobe. The contact resistance value for locally suspended graphene was estimated to be about 80 ƒÊƒ¶ cm2, which is 10000 times larger than that for surrounding graphene normally grown on SiC. The nonlinear current-voltage characteristics of the locally suspended graphene suggest tunneling junction formation between a metal nano-contact and suspended graphene. |  |
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Local conductance measurements of double-layer graphene on SiC substrate M Nagase, H Hibino, H Kageshima, and H. Yamaguchi, Nanotechnology 20 445704 (2009) |
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The microscopic structural and electrical properties of few-layer graphene grown on an SiC substrate were characterized by low-energy electron microscopy, transmission electron microscopy and scanning probe microscopy measurements of local conductance. The double-layer graphene sheet was confirmed to be continuous across the atomic steps on the buried SiC substrate surface, and the measured local conductance was clearly modified in the vicinity of the steps. The conductance decreased (slightly increased) at the lower (upper) side of the steps, suggesting deformation-induced strain is the origin of the conductance modification. From the contact force dependence of the conductance images, the effective contact areas for both nanogap-probe and point-probe measurements were estimated. |
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Direct actuation of GaAs membrane with the microprobe of scanning probe
microscopy K. Tamaru, K. Nonaka, M. Nagase,H. Yamaguchi, S. Warisawa, and S. Ishihara, Jpn. J. Appl. Phys. 48, 06FG06 (2009) |
| A method for evaluating the dynamic characteristics of micro- and nanoresonators with high spatial resolution is proposed. The mechanical resonance of circular micromembrane resonators is directly induced by voltage applied from the microprobe of a scanning probe microscopy (SPM) system. The vibration amplitude is simultaneously detected as height information by SPM. Experimentally, the resonant properties of fundamental and higher-order modes of 200-nm-thick GaAs micromembranes were measured. The frequency of the highest mode is 3.4 MHz and its resonant amplitude is about 1 nm. The resonant amplitude increases with increasing actuation voltage in a linear manner at voltages below 180 mV. Large actuation voltage induces nonlinear vibration with the spring soften effect, which originates from the strong attractive force induced by the electronic field between the probe and membrane. The high tapping force, which is repulsive, induces another type of nonlinear vibration caused by the spring harden effect. The simultaneous actuation and detection for mechanical resonators based on SPM technology reveals the characteristics of the mechanical interaction force between the micromembrane and microprobe. |  |
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In-plane conductance measurement of graphene nanoislands using an integrated nanogap probe M Nagase, H Hibino, H Kageshima and H Yamaguchi, Nanotechnology 19, 495701 (2008) |
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The in-plane conductance of individual graphene nanoislands thermally grown on SiC substrate was successfully measured using an integrated nanogap probe without lithographic patterning. A Pt nanogap electrode with a 30 nm gap integrated on the cantilever tip of a scanning probe microscope enables us to image a conductance map of graphene nanoislands with nanometer resolution. Single- and double-layer graphene islands are clearly distinguished in the conductance image. The size dependence of the conductance of the nanoislands suggests that the band gap opening is due to the lateral confinement effect. |
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Height dependence of Young's modulus for carbon nanopillars grown by focused-eon-beam-induced chemical vapor deposition K Nonaka, K Tamaru, M Nagase, H Yamaguchi, S Warisawa, and S Ishihara, Jpn. J. Appl. Phys. 47, 5116 (2008) |
| We investigated the height dependence of the Young's modulus for carbon nanopillars grown by focused-ion-beam-induced chemical vapor deposition (FIB-CVD) using phenanthrene gas as a source material. Carbon nanopillars of different heights were grown by FIB-CVD at various growth times and a fixed ion-beam focal point. The growth heights ranged from 3.6 to 35.6 ƒÊm. The diameters at the bottoms of the pillars were nearly the same, 100 nm, and it increased as the growth progressed. Young's modulus of the carbon nanopillars was evaluated from resonant frequency for mechanical vibration using uniform and nonuniform models. Young's moduli differed for different growth heights for both of the models. |  |