Effect of annealing temperature and time on the microstructure and photoluminescence(PL)properties of Al doped ZnO thin films deposited on Si(100)substrates by sol-gel method was investigated.An X-ray diffraction(XRD)was used to analyze the structural properties of the thin films.All the thin films have a preferential c-axis orientation,which are enhances in the annealing process.It is found from the PL measurement that near band edge(NBE)emission and deep-level(DL)emissions are observed in as-grown ZnO∶Al thin films.However,the intensity of DLE is much smaller than that of NBE.Enhancement of NBE is clearly observed after thermal annealing in air and the intensity of NBE increases with annealing temperature.Results also show that the PL spectrum is dependent not only on the processing temperature but also on the processing time.The DLE related defects can not be removed by annealing,and on the contrary,the annealing conditions actually favor their formation.
The polar interface optical （IO） and surface optical （SO） phonon modes and the corresponding Froehlich electron phonon-interaction Hamiltonian in a freestanding multi-layer wurtzite cylindrical quantum wire （QWR） are derived and studied by employing the transfer matrix method in the dielectric continuum approximation and Loudon＇s uniaxial crystal model. A numerical calculation of a freestanding wurtzite GaN/AlN QWR is performed. The results reveal that for a relatively large azimuthal quantum number m or wave-number kz in the free z-direction, there exist two branches of IO phonon modes localized at the interface, and only one branch of SO mode localized at the surface in the system. The degenerating behaviours of the IO and SO phonon modes in the wurtzite QWR have also been clearly observed for a small kz or m. The limiting frequency properties of the IO and SO modes for large kz and m have been explained reasonably from the mathematical and physical viewpoints. The calculations of electron-phonon coupling functions show that the high-frequency IO phonon branch and SO mode play a more important role in the electron phonon interaction.
