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Higher order VOn defects

The 889 cm-1 defect also anneals out around 450$^\circ$C, whereupon LVMs around 910, 976 and 1005 cm-1 (10K) are found. The intensities of these LVMs appear to be correlated. Another band at 986 cm-1 also arises but its intensity is not correlated with the other three. Corbett et al [141] assign the three LVMs to VO3 where Oi is trapped near the VO2 centre, since at this temperature Oi is now mobile. Thus VO2 does not dissociate but traps Oi. Support for this assignment is that the rate of growth of 976 cm-1 line is proportional to the product of the intensities of the 889 cm-1 line and that due to Oi [90]. However, the interpretation here is dependent on the assignment of the 889 cm-1 defect.

Further lines have also been seen and tentatively assigned to VO4 complexes, and a study of higher order VOn defects is currently underway by Lindström and Hallberg.

Chris Ewels