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Superconductivity and structure of n...

Murduck, James Matthew.

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Superconductivity and structure of niobium-nitride/aluminum-nitride multilayers.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Superconductivity and structure of niobium-nitride/aluminum-nitride multilayers./
Author:	Murduck, James Matthew.
Published:	Ann Arbor : ProQuest Dissertations & Theses, : 1988,
Description:	148 p.
Notes:	Source: Dissertations Abstracts International, Volume: 50-07, Section: B.
Contained By:	Dissertations Abstracts International50-07B.
Subject:	Condensation. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=8811496

Superconductivity and structure of niobium-nitride/aluminum-nitride multilayers.
Murduck, James Matthew.

Superconductivity and structure of niobium-nitride/aluminum-nitride multilayers. - Ann Arbor : ProQuest Dissertations & Theses, 1988 - 148 p.

Source: Dissertations Abstracts International, Volume: 50-07, Section: B.

Thesis (Ph.D.)--Northwestern University, 1988.

This item must not be sold to any third party vendors.

Multilayers of niobium nitride and aluminum nitride (NbN/AlN) are fabricated as a method to enhance the high field superconducting properties of NbN. NbN is of interest as a candidate for magnet applications involving fusion because of its excellent high-field transport properties and its tolerance to radiation and strain. Films are prepared by reactive d.c. magnetron sputtering and are shown to be well-layered superlattices by x-ray diffraction and electron microscopy. For d$\\sb{\\rm NbN} <$ 140 A the parallel critical fields are observed to increase with decreasing NbN layer thicknesses (d$\\sb{\\rm NbN})$ in good agreement with 2D Ginzburg-Landau theory. For some range of NbN thicknesses a dramatic increase in J$\\sb{\\rm c}$ is observed; the enhancement is more than an order of magnitude greater than thick NbN films. It is argued that the J$\\sb{\\rm c}$ enhancement arises from flux pinning in the AlN, or at the AlN/NbN interface, but not on defects in the NbN structure. Disorder is shown to exist within the NbN but primarily only for NbN layer thicknesses less than 60 A, as seen by transport properties and structural characterizations, and does not explain enhanced flux pinning for larger d$\\sb{\\rm NbN}$. Unlike thick NbN films, the flux pinning density is greater in the parallel rather than perpendicular field direction. This, along with the observation that the flux pinning density scales with the number of interfaces, is strong evidence that the flux pinning involves the AlN layers. Thermal stabilization, important to practical magnet design, is also accomplished in a novel structure by the addition of copper layers within the multilayer. These copper layers successfully prevent the samples from quenching at higher currents, while still maintaining the very high value of J$\\sb{\\rm c}$ in the parallel magnetic field direction (J$\\sb{\\rm c}$ = 1 $\imes$ 10$\\sp5$ at 21 T).Subjects--Topical Terms:

942542
Condensation.

Superconductivity and structure of niobium-nitride/aluminum-nitride multilayers.
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100 1 $a Murduck, James Matthew. $3 3546582
245 1 0 $a Superconductivity and structure of niobium-nitride/aluminum-nitride multilayers.
260 1 $a Ann Arbor : $b ProQuest Dissertations & Theses, $c 1988
300 $a 148 p.
500 $a Source: Dissertations Abstracts International, Volume: 50-07, Section: B.
500 $a Publisher info.: Dissertation/Thesis.
502 $a Thesis (Ph.D.)--Northwestern University, 1988.
506 $a This item must not be sold to any third party vendors.
506 $a This item must not be added to any third party search indexes.
520 $a Multilayers of niobium nitride and aluminum nitride (NbN/AlN) are fabricated as a method to enhance the high field superconducting properties of NbN. NbN is of interest as a candidate for magnet applications involving fusion because of its excellent high-field transport properties and its tolerance to radiation and strain. Films are prepared by reactive d.c. magnetron sputtering and are shown to be well-layered superlattices by x-ray diffraction and electron microscopy. For d$\\sb{\\rm NbN} <$ 140 A the parallel critical fields are observed to increase with decreasing NbN layer thicknesses (d$\\sb{\\rm NbN})$ in good agreement with 2D Ginzburg-Landau theory. For some range of NbN thicknesses a dramatic increase in J$\\sb{\\rm c}$ is observed; the enhancement is more than an order of magnitude greater than thick NbN films. It is argued that the J$\\sb{\\rm c}$ enhancement arises from flux pinning in the AlN, or at the AlN/NbN interface, but not on defects in the NbN structure. Disorder is shown to exist within the NbN but primarily only for NbN layer thicknesses less than 60 A, as seen by transport properties and structural characterizations, and does not explain enhanced flux pinning for larger d$\\sb{\\rm NbN}$. Unlike thick NbN films, the flux pinning density is greater in the parallel rather than perpendicular field direction. This, along with the observation that the flux pinning density scales with the number of interfaces, is strong evidence that the flux pinning involves the AlN layers. Thermal stabilization, important to practical magnet design, is also accomplished in a novel structure by the addition of copper layers within the multilayer. These copper layers successfully prevent the samples from quenching at higher currents, while still maintaining the very high value of J$\\sb{\\rm c}$ in the parallel magnetic field direction (J$\\sb{\\rm c}$ = 1 $\imes$ 10$\\sp5$ at 21 T).
590 $a School code: 0163.
650 4 $a Condensation. $3 942542
690 $a 0611
710 2 $a Northwestern University. $3 1018161
773 0 $t Dissertations Abstracts International $g 50-07B.
790 $a 0163
791 $a Ph.D.
792 $a 1988
793 $a English
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=8811496