Du-Cheng Tsai

Structures and Characterizations of TiVCr and TiVCrZrY Films Deposited by Magnetron Sputtering under Different Bias Powers

In this study, TiVCr and TiVCrZrY films were deposited on Si substrates by magnetron sputtering with the application of radio-frequency substrate bias of different powers from 0 to 15 W. The crystal structures, microstructure, and mechanical, electrical, and optical properties under the effect of bias were characterized. Both the TiVCr and TiVCrZrY films constructed simple solid solutions from all alloyed elements. The TiVCr films possessed a body-centered cubic crystal structure with a pyramid-like surface, while the TiVCrZrY films had a hexagonal close-packed crystal structure with a domelike surface. The microstructure and properties of the films varied with bias power. As the bias power increased, the microstructure of the films obviously changed from a porous to a dense columnar feature, and the density of the voids existing between the columns decreased. Accordingly, the physical properties of the films were improved. The hardness of the TiVCr and TiVCrZrY films was enhanced to about 11 and 14 GPa, and the electrical resistivity was lowered to 80 and 100 μΩ cm, respectively.

Effect of Annealing on the Sn-Doped TiO2 Films Prepared by DC/RF Cosputtering

Nb-doped titanium oxide (TiO 2 ) thin films were deposited on glass by dc/radio-frequency (dc/rf) magnetron cosputtering, in which dc and rf were utilized for Ti and Nb targets, respectively. The coated samples were postannealed at temperatures ranging from 473 to 773 K for 1 h in ambient air. Glancing incidence X-ray diffraction revealed a polycrystalline phase for the Nb-doped films postannealed at 523 K, in contrast to the undoped one that has to be annealed at 723 K, indicating that Nb dopant can enhance the crystallization of amorphous TiO 2 . Furthermore, the as-deposited Nb-doped film postannealed at 673 K was found to have an anatase-dominated phase with a fine-grain microstructure observed by transmission electron microscopy. Heat-treatment also induces a change in the surface morphology of the TiO 2 films examined by field-emission scanning electron microscopy. The optical properties of the TiO 2 films were characterized by UV/visible spectrophotometry. The average transmittance of the films is higher than 85%, and a small absorbance zone occurs in the visible region. Under visible light irradiation, all the Nb-doped TiO 2 films exhibit better photocatalytic activity than that of undoped ones. Among them, the Nb-doped TiO 2 film annealed at 673 K shows the best photocatalytic performance.

Investigation of the Characteristics of Undoped and Sn-Doped ZnO Films Prepared by an Acidic Sol

Transparent conducting thin films of undoped and Sn-doped zinc oxide films were prepared on glass substrate by a dip-coating method using an acidic sol. The effect of metal sources, zinc chloride (ZnCl 2 ) and zinc acetate dihydrate [Zn(OAC) 2 ·2H 2 O], on the crystalline structure and properties of the films was investigated in detail. X-ray diffraction analysis reveals that the acidic sol leads to ZnO crystals with a hexagonal wurtzite structure after annealing treatment. Transmission electron microscopy results evidence that the Sn-doped ZnO thin films are a mixed phase of wurtzite ZnO and tetragonal SnO 2 nanocrystals. Field-emission scanning electron microscopy shows that the morphology of the films is largely affected by the zinc metal sources, and optical and electrical properties of the films are closely related to their microstructure. The undoped films prepared with the zinc chloride source exhibit a lower transmittance in the visible wavelength between 600 and 800 nm, compared with that using the zinc acetate dihydrate source. The electrical resistivity of the undoped films is high (p > 2.0 X 10 4 Ω cm) but can be reduced by a Sn doping treatment. The optimum electrical resistivity of the Sn-doped films can reach to about 1.5 X 10 1 Ω cm.

A Study of Low-Temperature Sintering of (Ba0.6Sr0.4)(Ti0.94Cu0.06)O3 Ceramics with B2O3 Addition

The low-temperature sintering of (Ba0.6Sr0.4)(Ti0.94Cu0.06)O3 (BSTC) ceramics was investigated by conventional ceramics processing using a B2O3 sintering aid, and the dielectric properties and microstructures of the ceramics were examined. BSTC powders without B2O3 could not be fully densified at sintering temperatures lower than 1150°C. However, the addition of B2O3 markedly enhanced the sinterbility of BSTC powders, and the sintering temperature decreased from 1150 to 980°C. This may be due to the promotion of liquid-phase sintering. The 3 at.% B2O3-doped BSTC ceramics sintered at 980°C for 2 h exhibited a high density of 5.48 g/cm3. Transmission electron microscopy examination indicated that there are two kinds of secondary phases produced in BSTC ceramics during B2O3 addition; one is BaTi(BO3)2 with rhombohedral structure, and the other is Ba4Ti12O27 with monoclinic structure. The BSTC ceramics with 3 at.% B2O3 sintered at 980°C in air for 2 h exhibited a maximum permittivity, ϵ max = 1216, and a bulk density > 96% of theoretical density.

Influence of deposition parameters on the structure and optical property of Zn(S,O) films

This paper presents the influence of process parameters, including sputtering power, oxygen partial pressure (RO), and substrate temperature on the optical property of Zn(S,O) thin films fabricated by radio frequency magnetron sputtering technology and deposited on glass substrates. The chemical composition, structural and optical properties of the samples were investigated by electron spectroscopy for chemical analysis, X-ray diffraction, and spectrophotometer. All the films mainly exhibited β-ZnS phase with (111) preferred orientation. [S]/([S]+[O]) ratio increased at high sputtering power, low RO, and low substrate temperature. Moderate ranges in sputtering power and substrate temperature and low RO resulted in large grain size. Adatoms are expected to exhibit increased mobility under these conditions. Average transmittance exceeded 75% in the visible wavelength region. Bandgap under these conditions was dominated strongly by the change in grain size and [S]/([S]+[O]) ratio. Optical properties of Zn(S,O) thin films could be modified, which is promising for optoelectronic applications.