[Jlabsa_gs] **Reminder** Pizza Seminar - Wednesday, January 21, 2015 - A Message From Hari Areti
Jodi Patient
patient at jlab.org
Tue Jan 20 08:13:12 EST 2015
Jefferson Lab's Graduate Student and Post-Doc Association Wiki:
https://gspda.jlab.org/wiki/index.php/Main_Page
Please RSVP to: patient at jlab.org by COB on January 20, 2015
Wednesday, January 21 , 2015
***F113***
12:00-1:00 pm
John Musson
Jefferson Lab
"Deposition of Superconducting Nb Thin Films by Recrystallization and Abnormal Grain Growth"
Abstract: Superconducting (SC) niobium (Nb) thin films provide an attractive solution to
accelerator cavity manufacturability, but so far have been deficient in their radio-frequency
(RF) performance. Physical vapor deposition (PVD) techniques, such as sputtering, have been
largely favored, but have nearly always resulted in finite surface impedances, and lower
residual resistance ratios, (RRR) than bulk Nb. Recently, energetic condensation, and the use
of cold substrates has supported an alternative method for film growth, whereby an amorphous
film is grown beyond the thickness during which grain competition is completed. Laser-induced
re-crystallization of the film surface results large-grain crystalline structure, resembling
bulk Nb. In addition, abnormal grain growth in thin films is explored, whereby the interface
energies and initial film thicknesses are manipulated to favor radial (2-D) grain growth. The
resulting large-grain Nb (110) film provides a template for homo-epitaxial deposition, in order
to create thicker bulk-like SC films.
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