Experimental And Theoretical Research On Buffer Layer In Improving The Performance Of The Transparent Conductive Film

AZO films with TiO2 buffer layers were successfully prepared on glass substrates by radio frequency magnetron sputtering. The structure and surface morphology of films were characterized with XRD, SEM. The electrical and optical properties of films were measured with Hall Effect and UV-Vis Spectrophotometer. The effect of the thickness of the buffer layer on the properties of films was analysized. The samples were rapid thermal annealed in vacuum, The effect of the rapid thermal annealed on the properties of films was studied in detail. The samples prepared at room temperature were heated in air atmosphere, the effect of the change of temperature were studied, the effect of the buffer layer on the stability in films was analysized.X-ray diffraction indicates that the glass/TiO2/AZO films are polycryst-alline films. The thickness of AZO films was 610 nm. The ZnO (002) diffraction peak was observed in the angle of 20= 20°-80°range of X-ray diffraction pattern. The grain sizes of the films increased with the thickness of the buffer layer increased. Test results showed that glass/TiO2/AZO were n-type semiconductor films. When the thickness of TiO2 buffer layer was 3.6 nm, the resistivity of film reached a minimum value of 5.9×10-4Ω·cm, a remarkable 65.3% decreased compared with that without buffer layer. The band gap of the glass/AZO films and glass/TiO2(3.6 nm)/AZO films were 3.52 eV and 3.58 eV, respectively.The samples prepared at room temperature were rapid thermal annealed in vacuum at 500℃with 120 s. Compared to the as-deposited glass/TiO2/AZO, all annealed films had high merit figure. The (002) peak intensity of AZO films with TiO2 buffer layer was stronger than that of the films without TiO2 buffer layer, the resistivity of AZO films with TiO2 buffer layer decreased and the average transmittance increased slightly. The properties of as-deposited glass/TiO2(3 nm)/AZO film and annealed glass/ TiO2(3 nm)/AZO film were studied. It was found that the position of diffraction peak of annealed glass/TiO2(3 nm)/AZO film was closer to the standard value. After annealing, the grain size of glass/TiO2(3 nm)/AZO film increased, the stress and the resistivity decreased. Transmittance curves shifted to short wavelength, the absorption edge showed blue shift. The band gap of the as-deposited glass/TiO2(3 nm)/AZO film and the annealed glass/TiO2(3 nm)/AZO were 3.58 eV and 3.61 eV, respectively.The samples were heated in air atmosphere in a tube furnace with half an hour and the film stability was studied. The properties of films changed little when the heating temperature was below 300℃. When the heating temperature was higher than 300℃, the properties of films were destroyed. However, the sheet resistance increased slowly with the increase of the thickness of TiO2 buffer layer, while the average transmittance of the heated glass/TiO2/AZO films were maintained at 90%. At the same heating temperature, the grain size of the glass/TiO2(4.8 nm)/AZO film was larger than that of glass/AZO film. Absorption edge of glass/TiO2/AZO films shifted to the long wavelengths after the 400℃heated. The band gap of the glass/TiO2(4.8 nm)/AZO film was wider than that of the single AZO film after heated in 400℃.