Study Of Preparation And Optical Properties Of ZnO Coextruded Films

Zinc oxide(ZnO)is an importantâ…¡-â…¥semiconductor oxide with wide band gap. Its exciton binding energy(60 meV)is larger than that of GaN(25 meV)or ZnSe(22 meV).It is able to work effectively at room temperature(26 meV),and even at higher temperature.Its gain coefficient(300 cm^-1)is larger than that of GaN(100 cm^-1).The properties of ZnO as above stimulate a wide research interest in the study of short wave semiconductor laser material.Papers about ZnO are abounding in famous publications, such as Nature,Physical Review Letters and Applied Physics Letters.Professor Wiersma has token a special topic about ZnO random laser in NatUre.Professor Cao has observed the random lasing of ZnO semiconductor powder at the fluorescence experiment.In order to find high-quality low-cost ZnO film preparative methods,and further study on the applications of ZnO in optoelectronic devices,high-quality ZnO films have been deposited using TiO₂ and SiO₂ buffer layers by E-beam evaporation.The lattice mismatch and thermal mismatch were decreased by using buffer layer.And the luminescence characteristic of ZnO film was studied in this dissertation.Theoretically,a finite-difference time-domain(FDTD)method is used to study the resonance of loop random cavities of random laser.Maxwell-Bloch equations adaptive to random laser are presented.The threshold and number of saturation mode are studied.The results are as follows:The crystallinity of ZnO film deposited on quartz glass is considerably improved by using a TiO₂ buffer layer.The co-emission of UV,violet and green luminescence is observed from ZnO/TiO₂ film.When the Si was used as substrates,the ZnO films are amorphous.And the high-quality luminescence of amorphous ZnO film was observed. ZnO films have been deposited on Si substrates using amorphous SiO₂ as buffer layers, and thermal retardation was used to increase the optical quality of the ZnO film.PL spectroscopy showed that UV luminescence at only 374 nm was firstly observed.There are broad prospects for applications of ZnO in optoelectronic devices,especially in the UV light emitting devices and UV laser.The depolarization behavior of backscattered linearly polarized light from ZnO thin film was investigated experimentally.There is an optimal incident angle for depolarization of linearly polarized light with different wavelength,which is equal to their each effective Brewster's angle,respectively.It provides some references for studying the multi-scattering in disorder media.A finite-difference time-domain(FDTD)method is used to study the structure,consition of formation and mode characteristic of loop random cavities of random laser.It provides some theoretical basis for the design of random laser.A finite-difference time-domain method is used to solve Maxwell-Bloch equations.The localized modes and number of lasing modes are obtained.It provides some valuable references for studying the distribution of the spectrum of random laser.