Study On Photoelectric Properties Of Ion Implanted Polar ZnO Films

ZnO is a wide band gap II-VI semiconductor material,which is about 3.3 eV at room temperature,and exciton is up to 60 meV.ZnO has good photoelectric,transparent conductivity,gas sensitivity,and piezoelectric,and easy to achieve integrated.These excellent properties make ZnO materials have a large actual application value,such as ultraviolet detectors,pressure sensitive devices,surface acoustic waves.In recent years,people focus on the polarization structure and optical,electrical and magnetic properties of ZnO materials.A large number of experimental results show that doping can change the photoelectric properties of ZnO materials,especially for the band gap of ZnO films,doping can regulate the band gap of the material.The band gap of ZnO materials is very important in design and preparation of heterojunction,quantum well structure,and optoelectronic devices based on ZnO.Ion implantation is a very important doping method with the advantages of high concentration control accuracy,low temperature doping and good uniformity.It has unique advantages in the field of manufacturing semiconductor devices and integrated circuits.Since the asymmetry of the crystal structure of wurtzite ZnO,the spontaneous polarization of ZnO occurs along the c-axis,with ZnO[0001]Zn polarity and[000-1]O polarity.Different polarizers have differences in chemical and photoelectric properties.The thermal stability,doping efficiency and catalytic performance are all affected by the polarity.There are many preparation methods of polar ZnO films,among them,the molecular beam epitaxy method carried out under ultra-high vacuum conditions has low growth temperature,observing growth process,and high film formation quality.In this thesis,the properties of ion implanted polar ZnO films are explored by the following characterization methods.The structure of polar ZnO thin films was characterized by X-ray diffraction(XRD),and the grain size and lattice constant were calculated by the formula.The morphology of the films was observed by atomic force microscope(AFM).X-ray photoelectron spectroscopy(XPS)was used to qualitatively analyze the film composition.The optical properties of the polar ZnO film were analyzed by a spectrophotometer,photoluminescence(PL),and spectroscopic Ellipsometry(SE).In this paper,polar ZnO films were prepared by MBE,and inert Kr ions and transition metal Co ions were implanted into it by ion implantation to obtain ion-implanted polar ZnO film.The research results are as follows:1.After the Kr ion is injected into the O polar ZnO film,the surface form is changed from the planar shape,and the absorption of the ultraviolet region increases The band gap of the film is red shift after ion implantation,which may be caused by Kr ion implanted into the crystal lattice,which causes the crystal lattice to be broken and the crystal grains become smaller.In addition,the elliptical result shows that the film adds a transition peak at 3.56 eV,which may be caused by injection impurities.2.After Kr ion implantation of Zn polar ZnO film,the properties of the film change with the increase of Kr ion implantation concentration,and the surface pit morphology becomes more obvious with the increase of Kr ion concentration.The grain size change is small,indicating that most of the Kr ions are implanted at the Zn polar grain boundary.The absorption of the film increases,and the extinction coefficient increases.According to the results of spectral ellipsometry,it is found that the band gap is red-shifted after ion implantation,and the concentration has no obvious effect on the band gap.3.After transition metal element Co ion implanted different polar ZnO films,compared with pure ZnO material,Co ions partially replace Zn ions,causing the band gap of the film to become significantly smaller after ion implantation,and the band gap of the O polar film is smaller than Zn Polar ZnO film.The exploration of this thesis provides a reference for the application of ion implanted polar ZnO materials.