Some peculiarities of the near-band-edge emission from ZnO crystals grown on Si whiskers

The nature of the room-temperature near-band-edge emission from ZnO nanocrystals formed on Si substrates with whiskers is analysed. The peculiarities of the emission spectra of ZnO grown either directly on whiskers or on a substrate free of whiskers, as well as of ZnO grown on Si whiskers with Au globules on their tips, are studied and compared. Analysis shows that the phonon replica of free exciton emission makes a significant contribution to the luminescence spectrum of ZnO nanocrystals grown on whiskers, with homogeneous broadening dominating in this case. A comparison of the intensities of near-band-edge emission in the samples with and without gold showed that the presence of the latter enhances the emission by a factor of about 3.