Superluminescence and macroscopic exciton propagation in freestanding ZnO thin films

Khmelinskii, Igor; Makarov, Vladimir, I

http://hdl.handle.net/10400.1/16355

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Authors

Khmelinskii, Igor

Makarov, Vladimir, I

Abstract(s)

Recently we have reported properties of ZnO semiconductor films attached to CaF2 substrate. Presently we characterized absorption, emission and superluminescence of freestanding ZnO films, comparing these to the attached films with the same thickness values. The absorption spectra of the freestanding films had resolved bands, with the band density increasing with the nanofilm thickness. Additionally, the spectral transitions in these films were blue-shifted as compared to attached films. The absorption and emission spectra of freestanding films were resolved better than those of attached films, with the difference traceable to the surface roughness of the substrate used for deposition. We also explored exciton dynamics and propagation over macroscopic distances in freestanding films. The excitons lived longer and propagated further in freestanding films as compared to attached films. The superluminescence yield in freestanding 9.3 nm film of 0.43 +/- 0.05 was significantly larger than 0.17 +/- 0.03 in an equivalent attached film. We provided a detailed analysis of the results obtained. The reported data are unique, demonstrating significant difference in the optical properties of attached and freestanding ZnO thin films. Freestanding ZnO films are promising for optoelectmnic applications.