Chang-Soo Han

Direct attachment of carbon nanotube on scanning probe tip using dielectrophoresis

We found the simple, effective and low-cost fabrication method of scanning probe tip with carbon nanotube. The assembling apparatus has been discussed and a plausible explanation about attachment mechanism based on dielectrophoretic force has been suggested. In order to find the proper assembling condition, electric field analysis for the round shape tip has been accomplished. Using this condition, the scanning probe tips with carbon nanotube were fabricated at 25% success rate.

Reducing seek time of tracking actuator with pulsed excitation in optical disk

The latency time, which is the residual vibration of a fine actuator and track eccentricity, has been the aim for direct pull-in in optical disk systems. Modified velocity profiles of the coarse actuator and control inputs of the fine actuator have been proposed for the minimum residual vibration. Generally, there exists eccentricity due to mismatch of the disk center and the axis of a spindle motor. So, if a fine actuator is locked to the coarse actuator, another latency time must be need because of the track eccentricity. The track eccentricity can be estimated as the rotation type of the spindle motor changes from CLV to CAV. In this paper, the fine actuator is excited with the same velocity of the track and the track pull-in is executed without any latency.

Beam rotation actuator based on dove prism in the optical storage media

A beam rotation actuator, which can be utilized to improve the data transfer rate for optical disk systems, has been developed. The newly developed beam rotation actuator with high-resolution and fast response was assembled for micro positioning of an optical storage media. The beam rotation actuator is utilized to put multi-beam spots on more than one track on an optical disk simultaneously in addition to tracing multi-beam spots on tracks in a radial direction. Multi-beam spots turn on an optical axis by rotating dove prism in the optical path at the end of a cantilever arm. The beam rotation actuator is made of bimorph peizoelectric material. The dove prism is responsible for both high-resolution movement as well as multi-beam spot rotation. The dynamic equation of the beam rotation actuator is derived theoretically. The actuator is designed on the grounds of an analytical equation. It is shown that the beam rotation actuator has a natural frequency of 54 Hz or more, and the actuator has high-resolution. The application performance of the beam rotation actuator is verified as the feedback control is applied.

Fabrication and characterization of optoelectronic device using CdSe nanocrystal quantum dots/single-walled carbon nanotubes

In this paper, we fabricated the optoelectronic device based on Cadmium selenide(CdSe) nanocrystal quantum dots (NQDs)/single-walled carbon nanotubes(SWNTs) heterostructure using dieletrophoretic force. The efficient charge transfer phenomena from CdSe to SWNT make CdSe-Pyridine(py)-SWNT unique heterostructures for novel optoelectronic device. The conductivity of CdSe-py-SWNT was increased when it was exposed at ultra violet(UV) lamp, and varied as a function of wavelength of incident light.

The Attachment of Carbon Nanotube on a Blunt AFM Tip Using Electric Fields

We report a simple, low cost, reliable technique of making carbon nanotube (CNT) modified atomic force microscopy (AFM) tip. We used the dielectrophoresis and the electrophoresis to align and deposit carbon nanotubes on the end of the AFM tip. From the simulation and the various experiments, we obtained the optimal electric condition, 0.32Vpp/μm. Also, we found that the blunt shape of the tip’s apex is more effective than sharpened one. Through the experiments, we verified that the blunt shape is more effective over 50% than the sharpened one in the attachment of CNTs. By comparing the scanning results between the CNT modified tip and a normal AFM tip, we obtained the improvement in efficiency of 23%.Copyright

A new method for A single semi-conducting nanotube device

We report a new technology for the selective deposition of a semi-conducting single-walled carbon nanotube(SWNT) between two electrodes. This technology consists of two processes. First, to separate the most of metallic nanotubes from semi-conducting ones and align the nanotubes, we applied dc and ac voltage to the electrodes respectively. But, in spite of the separation of the metallic nanotubes from semi-conducting nanotubes, some of metallic nanotubes and semi-conducting nanotubes are still deposited together. The second process is to burn the metallic and semi-conducting nanotubes by applying the voltage between two electrodes which enable to obtain a single semi-conducting nanotube structure. We verified the trace of the burning by SEM images or AFM images, and checked the characteristic of semi-conducting nanotubes through the I-V characteristic graph.© 2004 ASME