Preparation And Characterization Of Zinc-Tin-Oxide Films By MOCVD

Science and technology are developing rapidly today. Semiconductor material development has gone through the first-generation element semiconductor represented by silicon and germanium, the second-generation compound semiconductor represented by GaAs and InP and the third-generation compound semiconductor represented by wide bandgap semiconductor which generally have higher breakdown electric field, thermal conductivity, electronic saturated rate and higher resistance ability to radiation. ZnO and SnO2 which belong to wide bandgap semiconductor oxide materials are important optoelectronic information material and have lots of applications in transparent conductive oxides.Transparent conductive oxide films require different performances for different applications. Each kind of transparent conductive oxides materials have certain characteristics, it's impossible to satisfy all the requirements. In order to develop TCO films for special purposes, some research group do with TCO materials for various combinations to prepare some TCO films with new features. Some binary TCO materials (such as ZnO, SnO2 etc) can be combined with various proportion and prepared using a variety of methods. The performance of TCO films are closely related with the chemical components. Zn-Sn-O film may also have both advantages of ZnO and SnO2. The chemical stability and photoelectric properties changed with the components changing. With certain conditions and certain proportion of Sn and Zn, the new ternary TCO material called zinc stannate can be formed. According to the different proportion of Zn and Sn, zinc stannate include two different structural crystals which belong to ZnSnO3 and Zn2SnO4 respectively.The major work and results are as follows:1. Zn-Sn-O films were prepared by metal organic chemical vapor deposition (MOCVD) method onα-Al2O3 (0001) substrate. During the experiments, high-purity tetraethyl tin ((C2H5)4Sn, purity≥99.9999%) was used as the organometallic source of Sn and high-purity diethyl zinc ((C2H5)2Zn, purity≥99.9999%) was used as the organometallic source of Zn. High-purity O2 (purity≥99.995%) was used as oxidant. High-purity N2 (purity≥99.999%) was used as carrier gas. Under specific temperature, the XRD spectra showed that when the proportions of Sn and Zn are 1:5,1:10 and 1:20 respectively, only ZnO (002) diffraction peak s observed. When the proportion of Sn and Zn is 1:1, ZnSnO3 (303) is observed. When the proportion of Sn and Zn is 1:1, we do experiments of variable temperature from 550℃to 700℃as well. SEM, transmittance and Hall effect were performed and structural, optical and electrical properties were discussed.2. When the proportion of Sn and Zn is 1:10, crystalline ZnO was formed. When the proportion of Sn and Zn is 1:1, crystalline ZnSn03 was formed. The samples were annealed in air at the temperature of 650℃and 800℃after deposition. The crystal quality of the ZnO film was improved as the annealing temperature increases. The ZnSnO 3 film began to resolve and generate Zn2SnO4 and SnO2 at 650℃. With the annealing temperature increasing to 800℃, ZnSnO 3 is resolved thoroughly.This completely accords with the thermal decomposition chemical equations as follows, 2ZnSnO3(?)Zn2SnO4+SnO2...