Fabrication And Properties Of Titanium Doped Zinc Oxide Thin Films By Radio Frequency Magnetron Sputtering

Zinc oxide （ZnO） is a kind of special direct-gap semiconductor material with wideoptical energy gap （about3.3eV） which can be used in thin film solar cells, liquidcrystal display （LCD）, LED displays, because of its high transmittance and lowresisitance properties. Besides, the cost of ZnO is much cheaper than the cost of ITOmaterial, and non-toxic advance makes it is preferred than other oxide thin filmmaterials as a new transparent counductive oxide （TCO） materials. The conductivity ofZnO will be enhanced when it is doped. The structural, optical and electrical propertiesof Ti-doped ZnO （TZO） thin films are investigated in this work.In this work, TZO thin films were fabricated in different contents by RadioFrequency （RF） magnetron sputtering on glass substrates. Structural, wettability,optical and electrical properties were investigated by X-ray diffraction （XRD）, contactangle measurement systerm, spectrophotometer and four-point probe, respectively. Thepurpose of the work is to find out the optimal condition for preparation. The results are,1. The results of TZO thin films prepared in different contents show that the crystalstructure of TZO films belongs to polycrystalline nature with hexagonal wurtzitephase as the crystal structure of ZnO. The strong （002） peak indicates apreferential orientation along c-axis for all the samples. The patterns of XRDindicate that Ti atoms substrate the place of Zn atoms in the lattices. The results ofcontact angles show that Ti doped can enhance the wettability and increase thesurface energy of the TZO films. The resistivity of the film decreases from1.049Ω·cm to4.706×10^-3 Ω·cm when Ti doped in the films. The transmissivity ofTZO films is larger than86%of visible wavelebgth range for3wt.%TZO filmswhich is the optimal contents in our work.2. The influence of different substrates temperatures on structural, optical andelectrical properties of TZO thin films was studied. The effect of differentsubstrates temperatures on the structure property is limited. With the substratetemperature increasing, the transmissivity of the thin films in the visiblewavelength range is increased. The TZO thin films are appropriate for fabricatingin the low substrate temperature, the sheet resistances are14.1/,13.6/,14.8/,28.2/and36.2/, respectively, when the substrate temperaturesare unheated,150C,200C,250C and300C. The optimal substrate temperature of the experiment is150C according to the values of figure of merits.The film resistivity is1.453×10^-3 Ω·cm, and the film transmissivity of visiblewavelength range is84.65%, the optical energy gap is3.5eV.3. The preparation and study of TZO thin films on different sputtering pressureconclude that the sputtering pressure is important to structural property, too largeor too small pressure will be the main reason for bad crystallinity and unfairness ofthe film surface. The sputtering pressure increases, the wettability of the samplesincrease. Considering both transmissivity and conductivity of all the TZO films,the optimal sputtering pressure is0.6Pa in our work.In conclusion, the optimal conditions for the preparation of TZO thin films are asfollows: the substrate temperature,150C; the sputtering pressure,0.6Pa; and thedoping content:3wt.%.