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Thickness-dependent blue shift in the excitonic peak of conformally grown ZnO:Al on ion-beam fabricated self-organized Si ripples
Basu T., Kumar M., Nandy S., Satpati B., Saini C.P., , Som T.
Published in American Institute of Physics Inc.
Volume: 118
Issue: 10
Al-doped ZnO (AZO) thin films of thicknesses 5,10, 15, 20, and 30nm were deposited on 500eV argon ion-beam fabricated nanoscale self-organized rippled-Si substrates at room temperature and are compared with similar films deposited on pristine-Si substrates (without ripples). It is observed that morphology of self-organized AZO films is driven by the underlying substrate morphology. For instance, for pristine-Si substrates, a granular morphology evolves for all AZO films. On the other hand, for rippled-Si substrates, morphologies having chain-like arrangement (anisotropic in nature) are observed up to a thickness of 20nm, while a granular morphology evolves (isotropic in nature) for 30nm-thick film. Photoluminescence studies reveal that excitonic peaks corresponding to 5-15nm-thick AZO films, grown on rippled-Si templates, show a blue shift of 8nm and 3nm, respectively, whereas the peak shift is negligible for 20-nm thick film (with respect to their pristine counter parts). The observed blue shifts are substantiated by diffuse reflectance study and attributed to quantum confinement effect, associated with the size of the AZO grains and their spatial arrangements driven by the anisotropic morphology of underlying rippled-Si templates. The present findings will be useful for making tunable AZO-based light-emitting devices. © 2015 AIP Publishing LLC.
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Published in American Institute of Physics Inc.
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