Study On Preparation Of Solution-Processed IGZO And IZO Thin Films

In recent years,the oxide thin-film transistors have gradually become a research hotspot due to the popularity of high-resolution flat panel displays,sensors,and large-area flexible electronic devices.One of the obvious advantages is the amorphous indium gallium zinc oxide thin film transistor?a-IGZO TFT?.Compared with the traditional polysilicon material,a-IGZO material which is active layer structure of TFT has a higher mobility(>10 cm²V^-1s^-1),good uniformity,high transmission in visible light,and adaptability to low temperature preparation.Solution process is one of the significant methods to achieve the preparation of large-area a-IGZO thin films with low process cost and temperature.The method by a solution process could be prepared in a large area,and has a lower temperature than a vacuum process preparation method such as magnetron sputtering.The IGZO and IZO thin films studied in this article were prepared by this process.In this thesis,effects of different annealing atmosphere and pressure treatment at same temperatures on microstructural and optical properties of the IGZO thin films fabricated by solution process were investigated.And the effects of the optical properties of IZO and IGZO/IZO thin films were studied at different annealing temperatures.The major content of this thesis can be summarized as follows.?1?The structure and conduction mechanism of IGZO and IZO thin films were briefly introduced.The advantages the of solution method for preparing thin films were analyzed in different films preparation processes The basic models for characterizing thin films were summarized as follows:Cauchy model,Bruggeman effective approximation model?B-EMA model?and Forouhi-Bloomer model?F&B model?.The optical properties and surface morphology of IGZO and IZO thin films were analyzed by ellipsometry?SC630?and atomic force microscopy?AFM?.?2?The effects of different annealing atmospheres and pressure on the optical properties of IGZO thin films were studied.The results indicated that compared with the 1.5 MPa-N₂atmosphere,the optical properties of IGZO thin films prepared under 1.5 MPa-O₂ atmosphere were superior.Observation of the surface morphology of the sample film by AFM showed the same trend.When the pressure was increased from 0.1 MPa-O₂ to 1.5 MPa-O₂,the thickness of the rough surface layer of the IGZO thin films decreased,and the optical bandgap of the thin films increased from 3.23 eV to 3.31 eV by F&B model analysis.It was further illustrated that the IGZO thin films could be superior under 1.5 MPa-O₂ atmosphere.?3?By changing the annealing temperature,the optical properties of the IZO thin films prepared by the solution process were studied and compared with the IGZO thin films prepared under the same conditions.The results indicated that when the annealing temperature increased from 220?to 300?,the refractive index and the optical band gap of the IZO thin films increased,and the extinction coefficient shifted to blue,in other words,increased the annealing temperature could improve the optical properties of the IZO thin films.?4?The effects of different substrate structures on the optical properties of IGZO and IZO thin films were studied.The IGZO/IZO thin films has superior optical properties,and the IGZO/IZO thin films is more dense as the annealing temperature increases from 220?to300?.