Q-size effect

The expression for AEg (eq. 5.4) has often been nsed to calcnlate the size of small semicondnctor particnlates for comparison with sizes measnred by transmission electron microscopy. Expression 5.4 works well for particles of diameter above -50 A (see e.g. Serpone et al., 1995a). The reasonable congmence notwithstanding, there are other plausible explanations for the observed bine shifts in the bandgap. Studies by Serpone and co-workers (1995a, 1995b) contended that the earlier reports of bine-shifted absorption thresholds, taken as evidence for Q-size effects in small Ti02 particles, may in fact be direct (Franck-Condon) electron transitions in an otherwise indirect-gap semiconductor. 

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