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Microstructural analysis and electrical conductivity of hexagonal WO 3 thin films during annealing
Author(s) -
AlMohammad Ahmad
Publication year - 2008
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.200723232
Subject(s) - annealing (glass) , materials science , transmission electron microscopy , thin film , arrhenius equation , conductivity , electrical resistivity and conductivity , crystal structure , crystallography , electron diffraction , activation energy , diffraction , hexagonal crystal system , hexagonal phase , analytical chemistry (journal) , nanotechnology , composite material , chemistry , optics , physics , engineering , chromatography , electrical engineering
WO 3 thin films have been deposited by thermal evaporation on (0001) surfaces of α‐Al 2 O 3 single crystal and annealed between 423 K and 623 K in air with a mean humidity of 50%. The structural and morphological properties of the films have been characterized by transmission electron microscopy and compatible selected area electron diffraction. During annealing, important changes in grain size and structure occur. As the annealing temperature increases slightly, the WO 3 ·1/3H 2 O structure successively transforms to hexagonal WO 3 and Magneli WO 3– x phases. During these structural transformations, the grains are constructed of twinned microdomains in different directions with largest lattice parameters of WO 3 . The conductivity of the WO 3 thin films has been investigated as a function of annealing temperature for each stable crystallographic phase. The activation energy for conduction deduced from the Arrhenius equation is found to be dependent on surface structure during various WO 3 phases. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)