Research On ZnO And The Related Multilayers Grown By Pulsed Laser Deposition

ZnO is an important wide gap material.Because of the wide band gap of 3.37 eV,large excition binding energy gap semiconductor of 60 meV,and high chemical stability,ZnO is an excellent candidate for the fabrication of nanoscale electronic and optoelectronic devices.The aim of this article is researching on ZnO and the related multilayers grown by pulsed laser deposition.The results are:1.The superlattices were directly grown by the pulsed laser deposition method.In low temperature PL,it can be observed that the coupling strength between excitons and longitudinal optical phonons is a decreasing function of wellwidth if the wellwidth is small. But if the superlattice was grown on the ZnO buffer layer,the buffer layer could not only increase the quality of superlattice,but also change the common morphology of the superlattice to the nanostructure morphology.Direction of the PL of superlattice is also almost perpendicular to the substrate and has nothing to do with the incident angle of the laser.This nanostructure would be useful for researching microcavity,or fabricating a 50-100 nm diameter beam of light with a strong orientation.2.ZnO/MgO multilayers samples were grown on sapphire(0001) substrate.The transmission and photoluminescence spectra show that the samples exhibit some Distribute Bragg Reflection phenomenon.3.ZnO films with different thickness MgO buffer layers have been grown on sapphire substrate.The SEM results show that the grain size in the direction parallel to the substrate surface increase with the MgO layer thickness.Thin MgO buffer layer and small growth rate of the ZnO layer are the key factors for depositing ZnO nanowires.The ZnO nanowires can be useful for frabricating solar cell.4.The MgO pores with thin ZnO layer at the bottom were also grown on sapphire.Thin ZnO layer on sapphire can form islands.When the substrate is sapphire,MgO is hard to be deposited on the ZnO small islands at high temperature and high vacuum.So this phenomenon can be used for fabricating the porous MgO.It is evident that porous material can be realized at high temperature and high vacuum by pulsed laser deposition method. Porous MgO can be used for fabricating the materials in which the shortest distance between the two nanoparticles is about 5 um. 5.The ZnO films coated with AlN layers were annealed.It can be observed from room temperature photoluminescence that the ZnO films coated with AlN layers do not show a deep level peak.Because the O atoms in ZnO surface would form oxygen and increase the concentration of oxygen vacancies,which is a donor defect in ZnO,by using the high temperature stability of AlN,the oxygen vacancies could be controlled for realizing the p-type ZnO.The peak at about 3.336 eV may be due to the dislocation.