Effect of the sputtering parameters on the physical properties and photocatalytic reactivity of TiO2 thin films prepared by an RF magnetron sputtering deposition method

Visible light-responsive TiO₂ (Vis-TiO₂) thin films were successfully developed by applying a radio-frequency magnetron sputtering deposition method by controlling various sputtering parameters such as the substrate temperature, Ar gas pressure, and the target-to-substrate distance. UV–Vis, XRD and SEM investigations revealed that optical property, the crystal structure, and photocatalytic activity of Vis-TiO₂ are strongly affected by the sputtering parameters during the deposition step. Vis-TiO₂ was found to act as an efficient photocatalyst for the H₂ and O₂ evolution from water under visible light irradiation (λ ≥ 420 nm). SIMS investigations have revealed that a slight decrease in the O/Ti ratio of the TiO₂ thin films plays an important role in the modification of the electronic properties of Vis-TiO₂ thin films, enabling them to absorb visible light.     

Orientation control of perovskite thin films on glass substrates by the application of a seed layer prepared from oxide nanosheets

Orientation control of perovskite compounds was investigated by the application of a seed layer prepared from oxide nanosheets. An aqueous suspension of oxide nanosheets was prepared by the exfoliation of a layered compound of KCa₂Nb₃O₁₀ oxide grains. A seed layer composed of (TBA)Ca₂Nb₃O₁₀ nanosheets (TBA = tetrabutylammonium) was formed on a glass substrate by simply dip coating it in the suspension. Two kinds of perovskite compounds, LaNiO₃ (LNO) and Pb(Zr,Ti)O₃ (PZT) with a preferred orientation of (00l) were successfully grown on this seeded glass substrate. In this study, the relation between lattice mismatch and electrical properties is investigated. A large, oriented PZT film with a size of 5 ×4 cm shows an improved P-E hysteresis behavior by use of this orientation control.     

Effect of swift heavy ion irradiation on the physical properties of CuIn(S0.4Se0.6)2 alloy thin films prepared by solution growth technique

Alloy thin films of CuIn(S_0.4Se_0.6)₂ material were deposited using the solution growth technique. The various deposition parameters such as pH of solution, time, concentration of ions and temperature have been optimized for the device grade thin films. The as-deposited films were annealed in a rapid thermal annealing (RTA) system at 450 °C in air for 5 min and subjected to high-energy Ag ion irradiations. Ag ion irradiation has been performed with an energy of 100 MeV at a fluency of 5×10¹² ions/cm² on the thin film. The changes in optical and electrical properties that occurred before and after post-deposition treatments in CuIn(S_0.4Se_0.6)₂ thin films were studied using X-ray diffraction (XRD) and AFM; increase in crystallinity was observed after annealing and irradiation. In addition, structural damages were observed in irradiated thin films. After annealing and irradiation, the surface roughness was seen to be increased. Decrease in resistivity was observed, which is consistent with the optical energy band gap. The results are explained by considering the high energy deposited due to the electronic energy loss upon irradiation, which modified the properties of the material.     

Effect of La3+ content on the properties of ferroelectric Bi4?xLaxTi3O12 (BLT) thin films prepared by aqueous chemical solution deposition

Lanthanum substituted bismuth titanate thin films were deposited using an aqueous chemical solution deposition method. Varying the composition of Bi_4−x La _x Ti₃O₁₂, with x = 0.5, 0.65, 0.75 and 0.85, is shown to have a large influence on the microstructure and properties of the films. Increasing the amount of La³⁺, x, from 0.5 to 0.85 led to a decrease of the remanent polarization (P _r) from 6.2 to eventually 0 μC/cm². This decrease of P _r is explained by means of X-ray diffraction (XRD) study, which shows that there is an increased preference for c-axis orientation upon increasing the La³⁺ concentration. Furthermore, a strong decrease of the grain size upon increasing x is observed in a scanning electron microscopic (SEM) study. The concurrent increase of domain pinning on the grain boundaries is a second effect which may be responsible for the deterioration of the ferroelectric property at larger x.