Xi Yao

Amorphous ferroelectric (Ba0.67Sr0.33)Ti1.02O3 thin films with enhanced H2 induced interfacial polarization potential

Ferroelectric (Ba0.67Sr0.33)Ti1.02O3 thin films have been prepared by the sol-gel technology and characterized using thermogravimetric analysis, differential thermal analysis, x-ray diffraction, dielectric characterizations, and gas sensing measurements. The (Ba0.67Sr0.33)Ti1.02O3 thin film capacitive devices are made on Si substrate to detect hydrogen gas and to study hydrogen induced interfacial polarization potential. Experimental results show that the Schottky I–V behavior appears in these Pd/amorphous (Ba,Sr)TiO3 thin film/metal capacitive devices, both in air and in diluted hydrogen gas environment, and that the enhanced interfacial dipole potential as large as 4.5 V at 1042 ppm hydrogen gas in air has been observed. Compared with the available data in the literature, the obtained value of hydrogen induced interfacial polarization potential in our experiment is about seven times larger than the best one reported under similar testing conditions. It has been clearly shown that the hydrogen induced in...

FT-IR, structure and dielectric property investigation of strontium zirconate thin films prepared by MOD technique

Abstract Strontium zirconate (SrZrO 3 ) oxide thin films on Pt/Ti/SiO 2 /Si substrate were prepared by the metal-organic decomposition wet chemical technology followed by post-annealing at different temperatures in flowing oxygen atmosphere. Strontium acetate Sr(CH 3 COO) 2 and zirconium (IV) acetylacetonate [CH 3 COCHC(O)CH 3 ] 4 Zr were chosen as precursors, separately and thoroughly dissolved in glacial acetic acid CH 3 COOH. Those prepared thin films were investigated using X-ray diffraction and Fourier transform infrared reflectivity spectroscopy to study the mechanisms of phase transformation and crystallinity, and using calculated dielectric constants and dielectric losses vs. sweeping frequency to study dielectric characteristics as well. The results show that the film annealed at 550 °C is amorphous with existing of carbonates, while annealed at 600 °C and above the carbonates are decomposed and those films crystallize into perovskite phase without preferred orientation. Dielectric results show that the films have their dielectric constants higher than 22.0 with very little dispersion in a frequency range from 100 Hz to 1 MHz.

Structural and gas-sensing properties of nanometre tin oxide prepared by PECVD

A low-temperature plasma-enhanced chemical vapour deposition (PECVD) technique has been employed to produce ultrafine tin oxide powders. The structural features and phase transition of this material have been characterized using differential thermal analysis (DTA), thermogravimetric analysis (TGA), X-ray diffraction, infrared spectroscopy (IR) and transmission electron microscopy (TEM). The oxygen absorption behaviour and gassensing properties have been investigated by electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy (XPS) and electrical measurements. Thick film gas sensors made from such ultrafine SnO2 powders yield better sensitivities than those of normal undoped SnO2 gas sensors. A gas-sensing reaction mechanism is also proposed.

d31 Type inplane bending multilayer piezoelectric microactuators—a design concept and its applications

Abstract A design concept for multilayer piezoelectric microactuator using piezoelectric coefficient d 31 was particularly stressed. Accordingly, two kinds of novel piezoelectric multilayer microactuators, called a split-morph and an annular split-morph, have been proposed and discussed for the dual stage actuation systems in high track density hard disk drives. The novel piezoelectric multiplayer microactuators possess a useful compromise performance to displacement, resonance frequency and generative force. Together with their thin plate-like features and low drive voltage, they are particularly suitable for mounting on the suspension of a head gimbal assembly (HGA) or between the flexure tongue and slider as the secondary fine-tuning actuator. The configuration, stroke and resonance frequency of the HGA integrated with the proposed microactuators have been described and introduced. The results reveal that the new design concept provides a valuable alternative for multilayer piezoelectric actuators.

Preparation and Characteristic Study of MOD Derived Dielectric SrZrO 3 Thin Films

We report in this paper our success in preparation of dielectric SrZrO 3 thin films on Pt/Ti/SiO 2 /Si substrates using wet chemical metallo-organic decomposition (MOD) technique and systematic characterizations in their structural development, optical band gap, and dielectric properties. The results of UV optical reflection spectroscopic measurement show the optical band gaps of these films are larger than 5.50 eV, which meets the requirement for the high-K CMOS application. These films exhibit very low leakage current density and high breakdown strength, such as the film annealed at 600°C has its low leakage current density of 4.2 2 10 m 10 A/cm 2 at the field strength of 580 kV/cm. The MOD derived SrZrO 3 thin films also have their dielectric constants higher than 22.0 with very little dispersion in a frequency range from 100 to 1 M Hz.

Investigation of influence of hydrogen gas on Pd/BST/Pt device by impedance spectroscopy

A new application using barium strontium titanate (BST) thin films to fabricate the Pd/BST/Pt heterostructure for hydrogen gas detection has been investigated. To further understand the mechanism of this novel hydrogen sensing properties, impedance spectroscopy of the Pd/BST/Pt has been systematically studied and interpreted satisfactorily based on an equivalent circuit model. The alternate current (AC) electrical data of the extracted parameters and the properties of dielectric permittivity are discussed. The influence of hydrogen on the impedance spectra demonstrates that the charges induced by hydrogen ions mainly occur at the interface rather than in the bulk of the film. These experimental results provide clear evidence for the hydrogen sensing mechanism in the Pd/BST/Pt capacitive device.

SPM studies on surface charge and local piezo-response of ferroelectric thin films

Abstract Ferroelectric (Ba0.67Sr0.33)TiO3 and Pb(Zr0.53Ti0.47)O3 thin films have been prepared by the RF magnetron sputtering process, and characterized using scanning probe microscopy. Two distinct grain-boundary space charge regions are observed in the BST films by the contact KPFM. Such charged grain-boundaries are correlated to their leakage current behaviors. The ferroelectric domain and retention properties of the PZT 53/47 thin films are also investigated using EFM. The time dependence of the remnant polarization is identified to follow a stretched exponential decay.

Domain imaging and local piezoelectric response of sol-gel PbTiO3 thin films using SPM

Abstract Ferroelectric PbTiO3 thin films have been prepared by sol-gel route, and characterized using scanning probe microscopy. The ferroelectric domain images are obtained in the piezo- response, phase and amplitude measurements respectively, and the resultant contrast is interpreted by the induced local domain piezo-vibration. In particular, 90° and 180° domain walls appear as a transition region and a dark region in the amplitude image with a thickness of 70 nm and 8 nm, respectively. In our randomly oriented PbTiO3 films, the local hysteresis loop measurements exhibit a variety of piezoelectric behaviors, and the additional non-switchable polarization is believed to originate from the asymmetric PbTiO3/Pt heterostructure. Moreover, PbTiO3 film shows an excellent polarization retention performance at the nanometer scale, which may be related to the high tetragonality of PbTiO3 structure.