Structure And Properties Of Doped Znic Oxide Films

TCO-doped ZnO films is one of the material which can replace ITO. It was widely used in many application, such as LCD monitor, solar battery, heat reflect mirror, electromagnetic shielding material and special function window. This paper had discussed the influence of different doped elements and different amount in the way of ceramic target preparation processing which could affect form TCO films. The thesis had used the traditional electronic ceramic manufacture method sintered X (X=Al2O3Ga2O3、B2O3) doped ZnO target, and deliberate the physical properties and microstructure characterization of those targets. Afterwards, different targets were used for deposited TCO films by Magnetron sputtering instrument. Finally, the author researched how the technological parameter affect the doped ZnO films’microscopic structure, film’s component and the the photoelectric properties. The related principle had been explained and some valuable experimental results was also achieved in experimental process.The conclusions are as follows:(1) Doped ZnO thin films were prepared by magnetron sputtering method. So the targets need to use doped ZnO powders by pressureless sintering at1395℃. The target’s performance had a direct effect on the merits of the films. Experiments show that sintering shrinkage of the ZnO powder is F=25%. the target diameter is60mm, homemade mold is Φ=80mm and heat the powder to1100℃before sintering with a certain gradient heating and insulation, then rubbed off the surplus amount and finally get the AZO and GZO target with the density of more than90%, the right size, and being available to DC magnetron sputtering method. As a binder to reduce shrinkage, PVP is easy to carbonize and form black spots during the sintering process in the surface of conductive ceramic target. During the preparation of BZO target, heating up445℃will make the boron oxide a large loss, loss of about50%, so the double content of the element boron were mixed when the experiment is designed. The AZO target of4%Al doping had the minimum sheet resistance of5-6Ω/□; the sheet resistance of the GZO target with the Ga-doped amount of4%was4Ω/□;the BZO target doped8%B gets of the optimal square resistance of32Ω/□;(2) The XRD analysis showed that the ZnO is wurtzite crystal structure, the doped elements caused the distortion of the crystal, and it shifts to syncline hexagonal system with the doping amount increase. In general, the ionic radius of Ga3+and Zn2+are closest, but in fact Al3+is easier to enter the lattice position of Zn2+. The diffraction peak at (002) of ZnO TCO film samples is most acute.(3) The average transmittance of visible light of prepared thin films is80%, the highest is83.7%, the optical and electrical properties of thin films were affected by slide substrate temperature, sputtering power and working pressure and other process parameters. The samples that their substrate temperature is250℃got maximum transmittance. UV cut-off boundaries move to the short wavelength direction with increasing temperature; the light transmittance of the film in visible light can be improved by improving the sputtering power, higher power made surface of the film gray; when argon pressure is1.0Pa, the film had the best performance, sheet resistance is6.08Ω/□, resistivity is6.08X10-4Ω cm, carrier concentration is4.840x1020cm-3the migration rate is21.96cm2(v· s)-1, thin film samples have "light trap" structure.(4) The optical and electrical properties of prepared GZO thin film are also subject to a variety of external conditions. Average visible transmittance of films is about85%. when substrate temperature is250℃, power is100W, the transmittance of films is87.07%,sheet resistance was7.9Ω/□, resistivity was6.559x10-4Ω·cm, The carrier concentration was1.311x1021cm-3, migration was7.26cm2(v· s)-1; With sputtering power increasing, the optical band gap decreases, the transmission range is narrower, the UV cut-off boundaries move to the direction of the long-wavelength and infrared cut boundaries move to the short wavelength direction; infrared move to the direction of the short wavelength cut-off boundaries because the increase in grain dense is higher when the temperature increased.(5) The best technological parameter of prepared BZO thin film was studied as follow: when substrate temperature is200℃, power is100W, the transmittance of BZO films is74.4%, resistivity was8.768x10-4Ω· cm, The carrier concentration was3.025x1020cm-3, migration was27.6cm2(v· s)-1(6) Optical and electrical properties is GZO> of AZO> BZO, the cost price is BZO <AZO <GZO; The surface microstructure, stability in hydrogen plasma atmosphere and excellent optical performance make it relatively more suitable as a thin-film amorphous silicon solar cell window layer material.