• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2004.07a
• /
• pp.101-104
• /
• 2004

We have fabricated a channel of superconducting flux flow transistor(SFFT) using the voltage-biased atomic force microscope(AFM) TiO tip and performed numerical simulations for the SFFT controlled by the magnetic field with a control current. The critical current density in a channel of the fabricated SFFT was decreased with the applied current by a control line. By comparing the measured with theoretical results, we showed a possibility of fabrication of an SFFT with a nano-channel using AFM anodization process technique.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.17 no.7
• /
• pp.782-787
• /
• 2004

Superconducting flux flow transistor (SFFT) is based on a control of the Abrikosov vortex flowing along a channel. The induced voltage by moving of the Abrikosov vortex in an SFFT is greatly affected by the thickness, the width, and the length of channel. In order to fabricate a reproducible channel in the SFFT, we studied the variation of the critical characteristics of ${YBa}_2{Cu}_3{O}_7-\delta(YBCO)$ thin films with the etching time using ICP (Inductively coupled plasma) system. From the simulation, it was certified that the vortex velocity was increased in a low pinning energy at channel width 0,5 mm. The surfaces of YBCO thin film were etched by ICP etching system. We observed the etched channel surfaces by AFM (Atomic Force Microscope) and measured the critical current density with etching time. As a measured results, the etching thickness of channel should be optimized to fabricated a flux flow transistor with specified characteristics.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2003.11a
• /
• pp.259-262
• /
• 2003

Superconducting flux flow transistor(SFFT) is based on a control of the Abrikosov vortex flowing along a channel. The induced voltage by moving of the Abrikosov vortex in SFFT is greatly affected by the thickness and width, of channel. In order to fabricate a reproducibility channel in SFFT, we have researched the variation of the critical characteristics of YBCO thin films with the etching time using ICP(Inductively coupled plasma) system. It was certified that the velocity of vortex decreased with increasing the width of channel and was saturated faster in low bias from a simulation. An etching mechanism of YBCO thin films by ICP system was also certified by AFM(Atomic Force Microscope) and by measuring the critical current density with etching time. As measurement result, we could analyze that we should optimize the etching thickness of channel part to construct a flux flow transistor with desired characteristics.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2001.07a
• /
• pp.921-926
• /
• 2001

The link for the Superconducting Flux Flow Transistor (SFFT) which is based on the flux flow has been fabricated by the ICP etching methods. The channel width and the thickness of the SFFT were a 3 ${\mu}$m and about 300 nm, respectively. The superconducting characteristic of the link was measured by the x-ray diffraction and the E.D.S.. The SFFT etched by ICP showed an I-V characteristic like the three terminal transistor.

• Transactions on Electrical and Electronic Materials
• /
• v.9 no.6
• /
• pp.260-264
• /
• 2008

The operational characteristics of superconducting amplifier using vortex flux flow were analyzed from an equivalent circuit in which its current-voltage characteristics for the vortex motion in YBCO microbridge were reflected. For the analysis of operation as an amplifier, dc bias operational point for the superconducting amplifier is determined and then ac operational characteristics for the designed superconducting amplifier were investigated. The variation of transresistance, which describes the operational characteristics of superconducting amplifier, was estimated with respect to conditions of dc bias. The current and the voltage gains, which can be derived from the circuit for small signal analysis, were calculated at each operational point and compared with the results obtained from the numerical analysis for the small signal circuit. From our paper, the characteristics of amplification for superconducting flux flow transistor (SFFT) could be confirmed. The development of the superconducting amplifier applicable to various devices is expected.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2002.07b
• /
• pp.1063-1066
• /
• 2002

An equivalent circuit for the superconductor flux flow transistor(SFFT) was combined with high temperature cooling device, based on the analogy between thermal and electrical variables using the high-temperature superconductor(HTS), is proposed. The device is composed of parallel weak links with a nearby magnetic control line. A model has been developed that is based on solving the equation of motion of Abrikosov vortices subject to Lorentz viscous and pinning forces as well as magnetic surface barriers. The use of thermal models the global performance of thermal cooling circuit and signal system to be checked by using electrical circuit analysis programs such as SPICE.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2007.11a
• /
• pp.895-902
• /
• 2007

Rotating machinery has two typical faults with clearance, one is partial rub and the other is looseness. Due to these faults, non-linear and non-stationary signals are occurred. Therefore, time-frequency analysis is necessary for exact fault diagnosis of rotating machinery. In this paper newly developed time-frequency analysis method, HHT(Hilbert-Huang Transform) is applied to fault diagnosis and compared with other method of FFT, SFFT and CWT. The results show that HHT can represent better resolution than any other method. Consequently, the faults of rotating machinery are diagnosed efficiently by using HHT.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2002.07a
• /
• pp.74-77
• /
• 2002

The channel of the superconducting Flux Flow Transistor has been fabricated with plasma etching method using ICP. The ICP conditions were 700 W of ICP power, 150 W of rf chuck power, 5 mTorr of the pressure in chamber and 1:1 of Ar : Cl$_2$, respectively. The channel etched by plasma gas showed superconducting characteristics of over 77 K and superior surface morphology. The critical current of SFFT was altered by varying the external applied current. As the external applied current increased from 0 to 12 mA, the critical current decreased from 28 to 22 mA. Then the obtained r$\sub$m/ values were smaller than 0.1Ω at a bias current of 40 mA. The current gain was about 0.5. Output resistance was below 0.2 Ω.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2003.07a
• /
• pp.561-564
• /
• 2003

본 연구는 고온 초전도 자속 흐름 트랜지스터의 채널 식각 두께에 따른 임계 특성의 자동 측정을 위해 나노옴/마이크로 볼트 미터 와 전원공급기 등 측정에 필요한 장비들을 GPIB 인터페이스 보드를 통해 PC와 연결하여 측정 장치를 구축후 직접 제작한 측정 프로그램을 통해 자동으로 시편에 전류, 전압을 가한후 임계 특성값을 효율적인 방법으로 측정하고 측정 결과값들을 시간순서 및 측정 대상에 따라 데이터 베이스화 하는 방법에 대하여 소개한다. 부수적으로 임계 특성의 정확한 측정을 위해 실험에 변수가 되는 요소들을 찾아내고 실험 데이터값들로부터 오차를 발견, 오차의 원인이 되는 식각 방법 및 실험 환경등의 부가적인 요소들을 고려하여 개선된 측정 장치를 구축하는데 경제적, 시간적인 효율성 측면에 대해 언급했다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.16 no.5
• /
• pp.424-428
• /
• 2003

The channel of a superconducting flux flow transistor has been fabricated with plasma etching method using a inductively coupled plasma etching. The ICP conditions then were ICP Power of 450 W, rf chuck power of 150 W, the pressure in chamber of 5 mTorr, and Ar : Cl$_2$=1:1. Especially, over the 5 mTorr, the superconducting thin films were not etched. The channel etched by plasma gas showed the critical temperature over 85 K. The critical current of the SFFT was altered by varying the external applied current. As the external applied current increased from 0 to 12 mA, the critical current decreased from 28 to 22 mA. Then the obtained trans-resistance value was smaller than 0.1 $\Omega$ at a bias current of 40 mA.