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Research on Manufacture of AZO Transparent Conductive Oxide Targets and Its Films

Author: SunYiHua
Tutor: XiongWeiZuo；LiChenHui
School: Huazhong University of Science and Technology
Course: Materials Science
Keywords: ZnO-Al2O3 mixed powder Dispersion behavior Slip casting Sintering AZO thin films Magnetron sputtering Optical and electrical properties Bilayers
CLC: TB383.2
Type: PhD thesis
Year: 2009
Downloads: 906
Quote: 3
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Abstract


In recent years, with LCD touch panels, organic light-emitting displays, solar cells, etc., makes the transparent conductive film to become one of the key material. Currently used tin-doped indium oxide (ITO) transparent conducting films of metal indium is a scarce resource, development has translucent conductive properties \As the zinc oxide group (ZnO) transparent conductive film relatively cheap price and exclude toxic, having quite excellent in development. Therefore, for the material and its preparation of zinc oxide thin film technology R \u0026 D, caused by the extensive attention. To this end, this paper has engaged in the following areas of research: the development of ultra-high density of ZnO-based ceramic target using the the colloidal processing plus pressureless sintering low-cost route; ZnO-based ceramic target and the development of ultra-high density magnetron sputtering; different process parameters on the performance of thin film; and try to study the preparation of double-layer transparent conductive film. The main conclusions are as follows: Zeta potential, viscosity, sedimentation test additive content, pH value, solid content and milling time 2 O 3 mixed powder of ZnO-Al stability, flowability, etc. of the body of water-based suspensions. The experimental results show that: the addition of polyacrylic acid (PAA), ZnO and Al 2 O 3 higher Zeta potential pH8 ~ 10.3 alkaline range, Zeta potential were lower than-45mV. Compared with the separately added PAA, while adding polyethylene glycol (PEG), ZnO and Al 2 O 3 Zeta potential did not change significantly. 0.2wt% of PAA is a saturated adsorption amount. PAA is a saturated adsorption amount, the suspension in the range of pH8 ~ 10.3 low viscosity, good stability. When the pH value of about 9, PAA mass fraction of from 0.20%, the lowest viscosity of the suspension, the best stability. Can be prepared by solid-phase volume fraction of 55% suspension. The increase in the amount of addition of polyethylene glycol, so that the viscosity of the suspension increases, stability decreases. The viscosity of the suspension of the exponential relation between the increase of the solid content is increased. Milling time 40h better. XRD analysis showed that α-Al 2 O 3 particles are uniform and stable distribution between ZnO particles. By optimizing the ZnO-Al 2 O 3 water-based suspension process parameters, slip casting dense green body was prepared, the final sintered ultra-high density of ZnO-Al 2 O 3 ceramic composite. The additive content of the green and the density and strength of the sintered body. ZnO-Al 2 O with 0.2 wt% of the polymer electrolyte of PAA and 0.2 wt% of the binder PEG dispersion prepared in pH9, 30vol% of the solids content under conditions 3 water-based suspension of the mixed powder, grouting molding a relative density greater than 66.6% of the uniform and dense green body, ZnO-Al 2 O 3 mixture of green particles uniformly dense. 0.2wt% PAA for ZnO-Al 2 O 3 saturation adsorption capacity of the mixed powder to form a good dispersion of slurry. Other hand, adding 0.2wt% PEG The green radial crushing strength increased to 12.5MPa, is conducive to the subsequent process. PH9, PAA and PEG added amount of all of which are under the process conditions of 0.2% of the system, the green body by 1 400 ℃ 2h insulation without pressure sintering the obtained almost fully dense sintered body (relative density greater than 99.7%) . Add 0.3% PAA (PAA slight excess), and to promote the improvement of the strength and density of the sintered body. Α-Al 2 O 3 and ZnO reaction products of ZnAl 2 O 4 pointed sintering process The Spar phase. Microscopic analysis revealed that the microstructure uniform, no abnormal grain growth and other defects, and aluminum elements are uniformly distributed. In the preparation of the thin film, the substrate temperature increased for the improvement of conductivity and the transmittance of the AZO film have a significant role in promoting. An appropriate increase in the substrate temperature, adatom migration energy, preferred orientation and doping favorable for thin-film crystalline quality. But the glass substrate temperature should not exceed 450 ℃. The substrate temperature reaches 400 ° C, the film resistivity of 10 -4 magnitude, the transmittance reaches 90% or more. AZO thin film optical bandwidth greater than undoped the ZnO films bandwidth (3.2eV) is caused by the Burstein-Moss effect. With the increase in the thickness of the film, the grain size increases, the grain orientation becomes good, good crystalline quality, is conducive to the decrease of the resistivity. Visible light transmittance with increasing thickness decreased gradually found Lambert law. When the thin film thickness and optical bandwidth decreases with the increase in the film thickness is caused by the quantum size effect. The resistivity of the film increases with the increase of the target-substrate distance. Target-substrate distance is not very obvious, the film transmittance transmittance change is mainly caused by the film thickness effect. AZO film resistivity with increasing sputtering power 400W range monotonous downward trend. Sputtering power increases are conducive to the improvement of the crystalline quality and Al doped. With increasing sputtering power, sputtering efficiency is improved, and the film thickness increases. Transmittance decreases with increasing sputtering power caused due to the effect of film thickness. The test does not appear 180W at minimum resistivity inflection point, the author uses ultra-high density related to the sputtering target. Within the working pressure of 0.1 ~ 1.0 Pa, the film resistivity in different sputtering power minimum values ??appear in an appropriate working pressure, the mean free path of the sputtered atoms and plasma gas coordinated decision between the average interatomic distance. Working pressure on the film transmittance and optical bandwidth is not very significant. 200 ℃ and 400 ℃ glass substrate coating, the lowest resistivity up to 5.3 × 10 -4 Ω. cm and 1.09 × 10 -4 Ω. cm. The magnitude of the resistivity of the film was increased, the decrease with the number of oxygen vacancies in a higher oxygen partial pressure conditions. Visible light transmittance is increased, and the partial pressure of oxygen helps the film under the conditions of the oxygen partial pressure, the thin-film crystal quality improvement, the relevant defect decreased. But the low partial pressure of oxygen (0.1% O 2 ) is not conducive to AZO film (002) preferred orientation. Different oxygen partial pressure the optical bandwidth changes may be related to stress changes in the film. Plus plated ZnO buffer layer is conducive to improving the quality of the AZO film crystallization, the (002) peak of preferred orientation and residual stress relaxation. ZnO buffer layer has little effect on the transmittance of AZO thin films, the average visible transmittance of about 90%. Substrate temperature of 250 ° C, respectively, in a 40mm or 60mm target group distance sputtered AZO film having a low resistivity (10 -4 ) and a high visible light reflectance (51%), can be prepared or higher resistivity (10 -3 ) and the transmittance (87%) of the ITO / AZO bilayer films. Adopted in the 400 ° C substrate temperature, 60mm target group from the AZO film was prepared, double-layer film having a high visible light transmittance (85 to 90%) and a low resistivity (10 -4 Cover level). When the thickness of the ITO / AZO ratio of 1:9, to obtain the lowest resistivity of 4.89 × 10 -4 ω. cm.

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