| Transparent conductive oxide films (TCOs) with high electrical conductivity, high optical transparence in the visible range and high optical reflectance in the infrared range have been widely used in flat panel displays and building glass. Among all the TCOs, indium tin oxide (ITO) has been widely used because of its low resistivity and high transmittance. However, indium is a scarce metal, which results in the high cost of ITO films. So, saving indium is an important topic.Recently, ZnO has been widely investigated because of its abundant and inexpensive. However, up to now, the optical and electrical properties of ZnO is not as good as that of ITO. With the development of flat panel displays, the TCOs are required to have reduced resistivity and sufficient transmittance. So, reducing the resistivity of TCOs is another important topic.This paper is focused on the following researches:(1) preparation of gallium doped ZnO (GZO)/Ag/GZO multilayer films, (2) preparation of ITO and aluminum doped ZnO (AZO) films with buffer layer, (3) preparation of yttrium doped ZnO (YZO) films.In chapter 3, GZO/Ag/GZO sandwich films were prepared on glass substrates by RF magnetron sputtering of GZO using a GZO target and ion-beam sputtering of Ag using an Ag target at room temperature. The structural property and morphology were measured with XRD and SEM. The electrical property was determined by four-point probe measurements. The optical ransmittance measurements were performed with a spectrophotometer. The dependence of structural, electrical and optical properties of the films on Ag layer, upper layer GZO and under layer GZO thickness has been studied in detail. The following conclusions can be drawn according to all experiments in this paper.1. The XRD spectra reveal that all the films are polycrystalline. The GZO layer is polycrystalline with a hexagonal structure and a preferred orientation of (002) with the c-axis perpendicular to the substrates. The Ag layer is cubic structure and has a preferred orientation of (111).2. Metal layer thickness plays an important role in determining the photoelectric property of sandwich films. In order to investigate the effect of Ag layer thickness on the properties of sandwich films, the thickness of under and upper layer GZO is fixed to 40 nm. With the increase of Ag layer thickness, the intensity of Ag (111) peak increases, the FWHM decreases, and Ag crystallite size increases, which implying improvement of the crystallinity of Ag layer. As the thickness of Ag layer increases from 6 to 10 nm, the resistivity of the films decreases from 2.4×10-4 to 9.0×10-5Ωcm, and the transmittance increases. When the Ag layer thickness increases further, the resistivity increases slightly, and the transmittance decreases. When the Ag layer thickness is 10 nm, the best photoelectric properties of the GZO/Ag/GZO sandwich films is obtained. Thus, the optimum Ag layer thickness is 10 nm.3. In order to investigate the effect of upper layer GZO thickness on the properties of sandwich films, the thickness of Ag and under layer GZO is fixed to 10 and 40 nm, respectively. As the thickness of upper layer increases from 20 to 60 nm, the intensity of (002) peak increases slightly, the FWHM decreases, and ZnO crystallite size increases. For all the films with different thickness of upper layer, the FWHM of Ag (111) peak and Ag crystallite size vary little, which suggests that the crystallinity of Ag layer is independent of the upper layer. As the thickness of upper layer increases from 20 to 30 nm, the average transmittance increases from 85.4% to 90.7%. As the upper layer thickness increases further, the transmittance decreases obviously. As the thickness of upper layer increases from 20 to 60 nm, the resistivity decreases monotonously. When the upper layer thickness is 30 nm, the figure of merit is the maximum. Thus the optimum thickness of upper layer is 30 nm.4. The thickness of Ag and under layer GZO is fixed to 10 and 30 nm, respectively. With the increase of under layer thickness, the intensities of ZnO (002) and Ag (111) peaks increase simultaneously, the FWHM of Ag (111) peak decreases and Ag crystallite size increases, which indicating the improvement of the crystallinity of Ag layer. Thus, the crystallinity of Ag layer is mainly determined by the under layer GZO crystallinity. With the increase of under layer thickness, the average transmittance shows a first increase and then decreases, and the resistivity increases monotonously. The GZO/Ag/GZO sandwich film with thickness of 40/10/30 nm owns the largest figure of merit with a resistivity of 5.6×10-5Ω2 cm and an average transmittance of 90.7%. 5. The changes in structural, optical and electrical properties of the sandwich films with the thickness of 40/10/30 nm at different post-deposited annealing temperature in vacuum were investigated. As the increase of annealing temperature, the intensity of (1 11) peak increases significantly and the intensity of (002) peak increases slowly. As the annealing temperature increases from 200 to 350℃, the intensity of ZnO (002) peak is weaker than that of Ag (111) peak. With the increase of annealing temperature, the FWHM decreases monotonously and the Ag crystallite size increases continuously, which implying that the crystallinity of Ag layer is improved obviously. With the annealing temperature increase from 100 to 350℃, the average transmittance of the films increases and the resistivity decreases. The lowest resistivity of 3.2×10-5Ωcm is obtained at the highest annealing temperature of 350℃.In chapter 4, the TiO2/ITO,ITO/ITO and AZO/AZO films were prepared on glass substrates by RF magnetron sputtering. The structural property and morphology were measured with XRD and AFM. The electrical property was determined by Hall effect measurements. The optical transmittance measurements were performed with a spectrophotometer. The dependence of structural, electrical and optical properties of the films on buffer layer thickness has been studied in detail.1. The XRD spectra reveal that all the TiO2/ITO films are polycrystalline. The thickness of all the ITO films is maintained constant at 180 nm. The ITO film favors (2 11) and (440) orientations without the TiO2 seed layer. When the TiO2 seed layer is applied, the crystalline structure of ITO films transforms into lower preferential structure with (211), (222), (400), (431), (440) and (622) etc. orientations. When the TiO2 seed layer thickness is 2 nm, the crystallite size of (211) and (440) peak is the largest, and the root mean square roughness (Rrms) of the film is larger than that of the glass/ITO film. With the increase of TiO2 thickness, the Rrms decreases firstly, then nearly maintains constant. When the TiO2 thickness is 2 nm, the resistivity of the film achieves minimum value of 3.4×10-4Ωcm due to both the increase of Hall mobility and carrier concentration. The resistivity of the ITO film with TiO2 seed layer of 2 nm has a remarkable 41% decrease comparing with that of the single layer ITO film, and the transmittance is about 93.1%. 2. The XRD spectra reveal that all the ITO/ITO films are polycrystalline. The thickness of all the ITO films is maintained constant at 250 nm. The Rrms of the film is larger than that of the glass/ITO film. As the buffer layer thickness increases from 0 to 20 nm, the resistivity of the film decreases from 3.8×10-4 to 2.7×10-4Ωcm. As the buffer thickness increases further to 32 nm, the resistivity increases to 4.2×10Ωcm. The resistivity of the ITO film with homo-buffer layer of 16 nm has a remarkable 30% decrease comparing with that of the single layer ITO film.3. The thickness of all the AZO/AZO films is maintained constant at 400 nm. The XRD spectra reveal that all the films are polycrystalline with a hexagonal structure and a preferred orientation with the c-axis perpendicular to the substrates. As the buffer layer thickness increases from 0 to 66 nm, the diffraction angle of (002) peak varies from 34.20°to 34.28°, the crystallite size increases from 26.1 to 47.1 nm, and the stress decreases from 3.03 to 1.88. As the buffer thickness is 66 nm, crystallite size achieves maximum implying that the crystallinity of the film is the best. As the buffer layer thickness increases further, the crystallite size decreases and the stress increases. Comparing with AZO film without buffer layer, the AZO film with the homo-buffer layer of 66 nm has a remarkable 59% decrease in resistivity. The transmittance of all the films exceeds 90.0%.In chapter 5, the YZO films were prepared on glass substrates by RF magnetron sputtering using an YZO target (ZnO:Y2O3=97:3 wt %). The structural property and morphology were measured with XRD and SEM. The electrical property was determined by Hall effect measurements. The optical transmittance measurements were performed with a spectrophotometer. The following conclusions can be drawn according to the experiments in this paper.The film thickness was 600 nm for all the samples. The RF power is maintained constant at 100 W As the deposition pressure increases from 0.8 to 2 Pa, the resistivity decreases from 1.3×10-3 to 8.9×10-4Ωcm. When the deposition pressure increases from 2 to 3 Pa, the resistivity shows a little increase. The deposition pressure is maintained constant at 2 Pa. As the RF power increases from 40 to 50 W, the resistivity decreases from 1.0×10-3 to 8.7×10-4Ωcm. However, when the power increases from 60 to 110 W, the resistivity varies little, and it is 9.0×10-4Ωcm or so. It can be concluded that the optimum deposition condition is as follows:pressure is 2 Pa, and RF power is 50 W. The XRD spectra reveal that the film is polycrystalline with a hexagonal structure and has a preferred orientation with the c-axis perpendicular to the substrate. SEM image reveals that the surface morphology is a porous structure. The average transmittance in the visible range is about 92.3%.In conclusion, a new sandwich transparent conductive GZO/Ag/GZO film was successfully prepared by RF magnetron sputtering and ion beam sputtering. The lowest resistivity achieved is 5.6×10-5Ωcm. The resistivity of ITO and AZO films with buffer layer has a remarkable decrease comparing with that of the single layer films. A new transparent conductive oxide YZO film was successfully prepared by RF magnetron sputtering.
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