Key Engineering Materials Vol. 301

Abstract: Diffusion behavior at the interface of (001)-epitaxially grown (Ba,Sr)TiO3(BST)/electrode/buffer layer/Si thin films was examined by use of secondary ion-microprobe mass spectrometer (SIMS) and transmission electron microscope (TEM) attached with energy dispersive X-ray fluorescence spectrometer (EDX). As the (001)-epitaxially grown film, following three kinds of structure was grown; (1)BST/(La,Sr)CoO3(LSCO)/CeO2/yttria-stabilized zirconia(YSZ)/Si, (2)BST/PLD-deposited Pt/SrTiO3(ST)/LSCO/CeO2/YSZ/Si and (3)BST/sputter-deposited Pt/ST/LSCO/CeO2/YSZ/Si. For sample (1), uphill diffusion of Sr and Ti was observed at the interface of YSZ and SiO2. Diffusion of Co into CeO2 layer was also detected. These tendencies of diffusion were also observed for samples (2) and (3). In addition to these tendencies, apparent uphill diffusion of Co at the Pt layer was observed for sample (2). However, this diffusion was not observed for sample (3). It was also observed that oxygen diffusion was prevented for sputter-deposited Pt. On the other hand, oxygen diffusion was observed for PLD-deposited Pt.

Abstract: Epitaxial Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) thin films for electrooptic applications were fabricated on a Si substrate using buffer layers. The PMN-PT/SrRuO3/SrTiO3/(La,Sr)CoO3/CeO2 /YSZ/Si hetrostructure was fabricated by pulsed laser deposition. A PMN-PT thin film with a thickness of 2μm was successfully deposited. The optical characteristics of PMN-PT epitaxial film were measured by prism coupling method. The morphology of the PMN-PT films was drastically improved by introducing a mask between the target and substrate during the deposition. The PMN-PT thin film showed a columnar structure, where the width of each column was approximately 180nm. A refractive index of 2.48 with zero bias voltage was obtained for the epitaxial PMN-PT thin film using the prism coupler method.

Abstract: This paper describes the deposition of PZT/oxide electrode thin film capacitors on Si(100) substrate with a CSD (Chemical Solution Deposition). Highly (100)&(001)-oriented SRO/LNO electrode films with a perovskite structure were obtained by the annealing at 700 °C from a precursor solution of Sr and RuCl3·2H2O for SRO and from a precursor solution of La(NO3)3 and Ni(CH3COO)2 for LNO. In addition, highly (100)&(001)-oriented PZT/oxide electrode capacitor were deposited on SRO/LNO/Si substrate by annealing at 650 °C, showing a good ferroelectricity of Pr=22μC/cm2 and Ec=55 kV/cm. In addition, the resultant PZT/oxide electrode thin film capacitors exhibited no fatigue up to 108 switching cycles.

Abstract: Micromachined sensors are a new generation of sensor technology combining existing integrated circuit fabrication technology with novel deposition and etching processing. In the viewpoint of low-power operation, high sensitivity and fast response speed of thermoelectric hydrogen sensor (THS), we prepared the micromachined thermoelectric hydrogen sensor (micro-THS) with the combination of the thermoelectric effect of SiGe thin film and the Pt-catalyzed exothermic reaction of hydrogen oxidation. The power consumption of the micro-THS was greatly reduced to be 50 mW for 100 °C operating, by the Pt-micro-heater on single membrane. The micro-THS with 40 wt.% Pt/alumina catalyst showed voltage signal of 10 mV for 1 % H2 in air.

Abstract: To integrate the ceramic Pt/alumina catalyst on micro-hotplate of micro-thermoelectric hydrogen sensor (micro-THS), a dispenser technique was used in this study. This micro-THS with the Pt/alumina catalyst is capable of sensing wide range hydrogen concentration of 50 ppm to 3 % at room temperature. For hydrogen/air mixture gas of 50 ppm, voltage signal is measured to be 0.03 mV at room temperature.

Abstract: The effects of Mn and Co addition on the electrical degradation of ZnO varistors were investigated on the basis of voltage-current (V-I) characteristics, X-ray diffraction (XRD), capacitance-voltage (C-V) characteristics, and isothermal capacitance transient spectroscopy (ICTS). The optimum Co content for preventing electrical degradation was determined to be approximately 0.5mol% in Bi-Mn(0.5mol%)-Co(0~1.0mol%)-added ZnO varistors. Correlations between the improvement of electrical degradation and the structural changes of additives were investigated by XRD. It is suggested that the crystal structure of a-Bi2O3 at the grain boundary changes to a different structure, such as d-Bi2O3 or Bi7.65Zn0.35O11.38 with a fluorite-type structure, at the optimum Co content. It is speculated that the structural change of Bi2O3 at the grain boundary contributes to the improvement of electrical degradation characteristics. Three trap levels were detected in all Bi-Mn-Co-added samples by ICTS. These trap levels showed a local maximum at the optimum Co content.