Preparations Of ITO And AZO Target Nanopowders And Growth Of Ⅲ-Ⅴ Semiconductor Alloy Films

This dissertation is focused on the preparations of ITO and AZO tagetnanopowders and the growth of III-V semiconductor alloy films, which is dividedinto two main directions. One is the preparations of large-scale SnO2and In2O3nanopowders for ITO target materials and ZnO nanopowders for AZO. The other isthe thermodynamic alalysis of ternary semiconductor alloys grown by SSMBE. Thereare four main parts in this work: the summaries of transparent conductive oxide thinfilm target materials; the preparations and process optimizations of ITO nanopowders;the preparations and process optimizations of AZO nanopowders; the study of III-Vsemiconductor alloy compounds grown by SSMBE. In the following, the primaryachievements in this dissertation are described.1. SnO2nanopowders of ITO target materials have been prepared byhydrothermal method with an autoclave. In the case0.5kg/batch production, theeffects of synthesis conditions including concentration of initial solution, pH value ofprecursor solution, reaction temperature, maximum pressure and reaction time ongrain size, particle morphology and crystal structure have been systematically studied.Unlike previous reports, some unusual dependences of the grain size of SnO2onreaction temperature and time have been found. There is a transition point (220℃) inreaction temperature effect on the production grain sizes. When the temperature isbelow220℃,grain sizes become larger with the temperature rising; when it is above220℃, on the opposite, grain sizes become smaller with the temperature rising. Andthere is also a transition point (12h) in reaction time effect. When the time is less than12h, SnO2particles begin to nucleate and grow up with the time rising; when the timeis more than12h, grain sizes become smaller with the time rising opposite.2. The batch preparations of In2O3nanopowders have been studied byhydrothermal method with an autoclave. The results show that the synthetic powdersby hydrothermal method are In(OH)3, and the hydroxides will be transformed intoIn2O3after sintering. By adjusting the sintering temperature, In2O3nanopowders canbe matched with SnO2nanopoeders, which lays the foundation for further sintering of the powder targets.3. ZnO nanopowders of AZO target materials have been prepared by directprecipitation method. The powders are characterized by means of X-ray diffractionand Scanning electron microscopy. The effects of synthesis conditions includingdifferent zinc salts as precursor, concentration of initial solution, solvent mixeddifferent proportions of ethanol and sintering temperature on grain size, particlemorphology and crystal structure have been systematically studied.4. A thermodynamic model for solid source molecular beam epitaxy growth ofternary III-V semiconductor alloys has been established. The energy of lattice strainand the decomposition of group-V element are both incoporated into this model, anda clear relational expression among growth temperature, flux ratio and alloycomposition is derivated. The calculation results are presented as well as comparisonswith existing experimental data. This setup model has some directions for the growthof other III-V semiconductor thin film materials.