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Title: Nanoscale compositional analysis of NiTi shape memory alloy films deposited by DC magnetron sputtering

The formation of surface oxide layer as well as compositional changes along the thickness for NiTi shape memory alloy thin films deposited by direct current magnetron sputtering at substrate temperature of 300 °C in the as-deposited condition as well as in the postannealed (at 600 °C) condition have been thoroughly studied by using secondary ion mass spectroscopy, x-ray photoelectron spectroscopy, and scanning transmission electron microscopy-energy dispersive x-ray spectroscopy techniques. Formation of titanium oxide (predominantly titanium dioxide) layer was observed in both as-deposited and postannealed NiTi films, although the oxide layer was much thinner (8 nm) in as-deposited condition. The depletion of Ti and enrichment of Ni below the oxide layer in postannealed films also resulted in the formation of a graded microstructure consisting of titanium oxide, Ni{sub 3}Ti, and B2 NiTi. A uniform composition of B2 NiTi was obtained in the postannealed film only below a depth of 200–250 nm from the surface. Postannealed film also exhibited formation of a ternary silicide (Ni{sub x}Ti{sub y}Si) at the film–substrate interface, whereas no silicide was seen in the as-deposited film. The formation of silicide also caused a depletion of Ni in the film in a region ∼250–300 nm just above the filmmore » substrate interface.« less
Authors:
;  [1] ;  [2] ; ;  [3]
  1. Centre for Nano Science and Engineering, Indian Institute of Science, Bangalore-560012 (India)
  2. Central Glass and Ceramics Research Institute, Kolkata-700032 (India)
  3. Defence Metallurgical Research Laboratory, Hyderabad-500058 (India)
Publication Date:
OSTI Identifier:
22224120
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Vacuum Science and Technology. A, Vacuum, Surfaces and Films; Journal Volume: 31; Journal Issue: 6; Other Information: (c) 2013 American Vacuum Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 77 NANOSCIENCE AND NANOTECHNOLOGY; ANNEALING; DEPOSITS; DIRECT CURRENT; ION MICROPROBE ANALYSIS; LAYERS; MAGNETRONS; MASS SPECTROSCOPY; NANOSTRUCTURES; NICKEL ALLOYS; SHAPE MEMORY EFFECT; SILICIDES; SILICON ALLOYS; SPUTTERING; THIN FILMS; TITANIUM ALLOYS; TITANIUM OXIDES; TRANSMISSION ELECTRON MICROSCOPY; X-RAY PHOTOELECTRON SPECTROSCOPY; X-RAY SPECTROSCOPY