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Title: Growth, structure, and high temperature stability of zirconium diboride thin films

Morphologically stable, electrically conductive thin films are required for emerging harsh environment sensors that can operate at temperatures above 1000 °C. Zirconium diboride (ZrB{sub 2}) is an ultrahigh temperature ceramic with a melting temperature greater than 3200 °C and in bulk form has an electrical conductivity of ∼10{sup 7 }S/m. Thin films of varying Zr:B ratio have been deposited on sapphire substrates by electron beam coevaporation from elemental sources. An appropriate ratio of the elemental fluxes was determined to produce nearly stoichiometric ZrB{sub 2} thin films. Films deposited at ambient substrate temperatures are amorphous as measured by x-ray diffraction, while films grown at 600 °C show textured ZrB{sub 2} nanocrystallites in an amorphous matrix, regardless of composition. When annealed in ultrahigh vacuum at 800 and 1000 °C for 1 h, nanocrystalline films show further grain growth with a 〈101{sup ¯}0〉 ZrB{sub 2} preferred orientation normal to the substrate, while the low nucleation rate in the amorphous films inhibits the formation of any substantial grains. Film conductivity ranges between 0.13 and 6.3 × 10{sup 5 }S/m, increasing with zirconium content and crystallite grain size. Besides grain growth, no micron-scale structural or morphological changes were observed with annealing, suggesting that ZrB{sub 2} films can act as stable electrodes in high temperaturemore » environments.« less
Authors:
; ;  [1]
  1. Department of Physics and Astronomy, and Laboratory for Surface Science and Technology, University of Maine, Orono, Maine 04469 (United States)
Publication Date:
OSTI Identifier:
22392179
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Vacuum Science and Technology. A, Vacuum, Surfaces and Films; Journal Volume: 33; Journal Issue: 3; Other Information: (c) 2015 American Vacuum Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ANNEALING; AUGMENTATION; DEPOSITS; ELECTRIC CONDUCTIVITY; ELECTRON BEAMS; GRAIN GROWTH; GRAIN ORIENTATION; GRAIN SIZE; MELTING POINTS; MORPHOLOGICAL CHANGES; NANOSTRUCTURES; SAPPHIRE; SUBSTRATES; TEMPERATURE RANGE 1000-4000 K; THIN FILMS; X-RAY DIFFRACTION; ZIRCONIUM; ZIRCONIUM BORIDES