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Processing and characterization of h...

Huh, Jeong-Uk.

Processing and characterization of high temperature superconductor thin films deposited by electron beam co-evaporation.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Processing and characterization of high temperature superconductor thin films deposited by electron beam co-evaporation.
Author:	Huh, Jeong-Uk.
Description:	134 p.
Notes:	Adviser: Robert Sinclair.
Notes:	Source: Dissertation Abstracts International, Volume: 67-05, Section: B, page: 2778.
Contained By:	Dissertation Abstracts International67-05B.
Subject:	Engineering, Materials Science.
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3219293
ISBN:	9780542706943

Processing and characterization of high temperature superconductor thin films deposited by electron beam co-evaporation.
Huh, Jeong-Uk.

Processing and characterization of high temperature superconductor thin films deposited by electron beam co-evaporation. - 134 p.

Adviser: Robert Sinclair.

Thesis (Ph.D.)--Stanford University, 2006.

Ever since the high temperature superconductors (HTS) were discovered in the late 1980s, there have been enormous efforts to make this into applications such as power transmission cables, transformers, motors and generators. However, many obstacles in performance and high manufacturing cost made this difficult. The first generation HTS wires had low critical current density and were expensive to fabricate. The motivation of this research was to make high performance and low cost second generation HTS coated conductor. Electron beam co-evaporation technique was used to deposit YBCO(YBa2Cu3O7-x ) film at a high rate (10nm/s and higher) on single crystals and metal tapes. The oxygen pressure at the stage of depositing Y, Ba, Cu was 5x10 -5 Torr and the process temperature was 810-840°C. In-situ Fourier Transform Infrared spectroscopy (FTIR) was used to monitor the optical properties of the YBCO during and after deposition. The deposit transformed to a glassy amorphous mixture of Y, Ba and Cu at 3 mTorr of oxygen. YBCO crystallization occurred after extra oxygen was applied to several Torr. FTIR showed almost the same signature during the formation of YBCO and liquid Ba-Cu-O during deposition, which indicates the liquid played an important role in determining the properties of YBCO in terms of providing epitaxy and fast transport of atoms to nucleate on the film-metal interface. The transformation was very rapid---seconds to minutes, compared to minutes to hours for other post-reaction processes. The oxygen partial pressure and the rate of oxidation (supersaturation) in the liquid region defined in the YBCO phase stability diagram determined the electrical and microstructural properties. In-situ X-ray diffraction heating stage with ambient control was utilized to study this supersaturation effect and explore the temperature-pressure space during YBCO growth. With all the information gathered from FTIR and XRD in-situ experiments and also with nano-engineering during deposition, the growth process was optimized in the evaporator. As a result, one micron thick YBCO with critical current density of 1.1 MA/cm2 was successfully grown on metal tape. TEM analysis showed a growth mode and microstructure suggestive of lateral growth.

ISBN: 9780542706943Subjects--Topical Terms:

226940
Engineering, Materials Science.

Processing and characterization of high temperature superconductor thin films deposited by electron beam co-evaporation.
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