Yoshiharu Shirakawabe

Self-sensing piezoresistive cantilever and its magnetic force microscopy applications

A newly developed Si self-sensing piezoresistive cantilever is presented. Si piezoresistive cantilevers for scanning microscopy are fabricated by Si micro-machining technique. The sensitivity of the piezoresistive cantilever is comparable to the current laser detecting system. Topographic images are successfully obtained with the piezoresistive cantilever and some comparisons are made with the laser detecting system. Furthermore, the magnetic film (Co-Cr-Pt) is coated on the tip of the piezoresistive cantilever for magnetic force microscopy (MFM) application. The magnetic images are successfully obtained with the self-sensing MFM piezoresistive cantilever. The self-sensing piezoresistive cantilevers have been successfully applied in scanning probe microscopy and MFM.

Nano-Four-Point Probes on Microcantilever System Fabricated by Focused Ion Beam

We have developed a new cantilever system for scanning probe microscopy. The microcantilever system designed for electrical resistivity measurements of nanomaterials has 16 electrodes and dual cantilevers. One cantilever with four additional electrodes is for the resistivity measurement in the four-point-probe mode. The other lever is for surface observation. The contact forces of both the levers are controlled by a piezoresistor in the self-sensitive detection mode. The nano-four-point probes on the electrical measurement lever are fabricated by using a focused ion beam. The width of the probe electrode is approximately 200 nm. The distance between the probes is approximately 300 nm. The feasibility of electrical measurements is confirmed by measuring the contact characteristics using a graphite sample.

Applications of high-resolution MFM system with low-moment probe in a vacuum

Magnetic force microscopy (MFM) is very useful for observing magnetic domain structures. However, due to stray fields from an MFM probe, observations of small magnetic domain structures are limited. The authors have developed a high-resolution MFM system that utilizes a low-moment probe and a quality (Q)-controlled prove driver, which allows high-quality measurement in a vacuum without disturbing domain structures. Using this system, a resolution finer than 20 nm was achieved. In this paper, the advantages of this MFM are demonstrated using a Permalloy honeycomb nanonetwork and a Permalloy semicircular loop.

Performance of the carbon nano-tube assembled tip for surface shape characterization

The carbon nano-tube (CNT) has ideal properties for atomic force microscope (AFM) tips. We assembled a CNT using 2 three-axial manipulators in a scanning electron microscope (SEM) chamber. In this process, the length and angle of the CNT were adjusted by observing the SEM image, after which the CNT was glued by amorphouscarbon. The results of performance are as follows. The lifetime of the CNT tip proved to be 5 times better than that of the silicon tip when continuously measuring the micro-roughness of a Czochralski (Cz) P-type (100) silicon wafer. The CNT tip is able to trace a narrow space (width less than 1 microm) better than the conventional silicon tip because of its high aspect ratio. The relationship between the observed image and CNT geometry is discussed herein.

Advanced tip design for liquid phase vibration mode atomic force microscopy.

We have fabricated polymer tips for atomic force microscopy in order to elucidate the effects of tip length and shape on cantilever vibration damping in liquids. The vibration damping is investigated by measuring the vibration amplitude of cantilevers as a function of tip-sample distance. The cantilever with a short tip provides a higher damping effect over long tip-sample distances. When the vibration amplitude was rescaled to show the effect of the cantilever width on oscillation damping, the vibration amplitude of cantilevers with various tip lengths was similarly obtained in a long distance range over 50 microm. This similarity is explained by an acoustic damping model in which an acoustic wave is generated by the cantilever. Finally, the results indicate a cantilever with a sufficiently long tip compared to the cantilever width can dramatically reduce the long-range damping effect in a liquid environment.

Applications of high-resolution MFM system with low moment probe and Q-control in vacuum

Magnetic force microscopy is performed on Permalloy honeycomb nanonetwork and Permalloy semicircle wire loop using low momentum probe Q-control in vacuum. The new method is executed without disturbing the magnetic domain structure of the samples.