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To achieve significant reduction of dielectric loss and enhancement of dielectric tunability for actual applications, a Ba 0.51 Sr 0.34 TiO 3 film modified by Y/Mn alternate doping (Y/Mn-BST 0.85 ) is prepared by an improved sol-gel method, where the film is composed of 12 layers, and odd number layers are preheated. For comparison, BST 0.85 , Y-BST 0.85 and Mn-BST 0.85 films are also prepared. XRD shows four films are ABO 3 cubic perovskite structures. The BST 0.85 film shows the smallest lattice parameter and donor doping because rich Ti 4+ ions enter into A sites to replace some Sr 2+ and Ba 2+ ions. Besides the donor doping, three doped BST 0.85 films exhibit slightly larger lattice parameters and acceptor doping because Y 3+ or Mn 2+ ions replace some Ti 4+ ions at A sites. The Y/Mn-BST 0.85 film shows the largest lattice parameter and the strongest crystallinity because Y-BST 0.85 layer and Mn-BST 0.85 layer match well in lattice structure. Compared to stoichiometric films, four nonstoichiometric films show markedly decreased dielectric losses. The Y/Mn-BST 0.85 film exhibits the lowest dielectric loss with 0.45 ~ 0.54% under the conditions of − 40 to 40V and 100 kHz, and 0.43 ~ 2.29% under the conditions of 10 Hz ~ 1 GHz and 0 V, thus can satisfy actual applications including tunable microwave application at high frequencies. The related mechanisms are studied by measuring leakage current density, observing AFM and analyzing XPS besides analyzing the XRD patterns. [ABSTRACT FROM AUTHOR]

Abstract: Mn and Y alternately doped Ba0.6Sr0.4TiO3 (Mn/YBST) films were prepared by improved sol–gel method on Pt/Ti/SiO2/Si substrates. The effect of different doped concentrations (0.5%, 1.0%, 1.5%, 2.0% and 2.5%) on crystallization and dielectric properties of BST films was studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and HP4294A. All films grow along (110) orientation, possessed dense nodular microstructure, exhibited decreased grain size and improved morphologies with smaller average roughness. As a result, the doping behavior changes from donor doping to acceptor doping and again to donor doping and the dielectric constants and the dielectric losses tend to decrease with increasing doped concentration. 1.5% corresponds to the optimized dielectric properties with the dielectric losses of about 0.007 and the figure of merit (FOM) of 38.83 at 100kHz. Also, the related mechanisms and the dielectric properties at microwave frequencies are discussed. [Copyright &y& Elsevier]

Smooth and dense preheated cerium (Ce) and manganese (Mn) codoped barium strontium titanate (CeMn-BST) films with various thicknesses have been prepared by improved sol-gel method. Capacitance-voltage curves show that with increasing film thickness, combination of dielectric properties are significantly improved with optimized values of about 1300 moderate permittivity, less than 0.007 dielectric loss, more than 58% tunability and hence near 180 figure of merit (FOM) for eight-layer CeMn-BST film. The objective of this paper is to study the improved mechanisms for such excellent dielectric properties. XRD shows that the films layered-grow mainly along (110) orientation and exhibit ABO3cubic perovskite structure. As film thickness increases, Ce3+and/or Mn2+ions are showing doping modes from donor doping to acceptor doping, the crystallization of films is enhancing, but the average grain sizes of the films show gradually decreased trend from about 45nm to 25nm in terms of the intensities of (110) diffraction peaks. AFM indicates that the films are getting smoother with smaller roughness with increasing thickness. XPS reveals that the films reveal decreased non-perovskite structure, element core levels and Fermi levels with increasing thickness. Leakage current densities are significantly decreased almost at two orders of magnitude with increasing thickness. Pure BST films are compared. [ABSTRACT FROM AUTHOR]

Vanadium oxide thin films have been deposited by reactive DC magnetron sputtering. The results showed that the sputtering voltage has a special change behavior in Ar condition and Ar/O2mixed conditions. With O2gas flow input instantaneously, the sputtering voltage climbs quickly, and then tends to be stable shortly. Also, the sputtering voltage evolution appears a hysteretic loop characteristics with O2gas supplied increasing and decreasing. The sputtering voltage behavior observed is related to the ion induced secondary electron emission (ISEE) coefficient of the target material. The ISEE coefficient of the oxidized vanadium on target surface is lower than the ISEE coefficient of the pure vanadium metal, which is not in agreement with the generally accepted idea that the ISEE coefficient of oxides is much larger than for metals. [ABSTRACT FROM AUTHOR]

Abstract: Ba0.6Sr0.4TiO3 thin films were deposited on Pt/SiO2/Si substrate by radio frequency magnetron sputtering. High-resolution transmission electron microscopy (HRTEM) observation shows that there is a transition layer at BST/Pt interface, and the layer is about 7–8nm thickness. It is found that the transition layer was diminished to about 2–3nm thickness by reducing the initial RF sputtering power. X-ray photoelectron spectroscopy (XPS) depth profiles show that high Ti atomic concentration results in a thick interfacial transition layer. Moreover, the symmetry ν of ɛ r–V curve of BST thin film is enhanced from 52.37 to 95.98%. Meanwhile, the tunability, difference of negative and positive remanent polarization (P r), and that of coercive field (E C) are remarkably improved. [Copyright &y& Elsevier]