W. X. Cheng

Optical and electrical properties of ZnO nanocrystalline textured films prepared by DC reactive magnetron sputtering

ZnO thin films were deposited by DC reactive magnetron sputtering using a metal zinc target. The crystallinity microstructure and surface morphology of ZnO thin films were investigated by X- ray diffraction (XRD) and scanning electron microscopy (SEM). The composition of ZnO thin film was characterized by XPS. The optical properties of ZnO thin film were obtained by spectroscopy ellipsometry and UV-VIS spectrometry. The optical bandgap was found to be 3.29eV of direct-transition type. The low frequency (1kHz- 100kHz) dielectric properties of ZnO thin film were also discussed. The dielectric constant and dielectric loss at 10kHz are 13.4 and 0.03 respectively.

IMPRINT PROPERTIES OF YTTRIUM DOPED PZT THIN FILM

ABSTRACT Undoped and yttrium (Y) doped PZT (40/60) thin films have been deposited by spin-coating on Pt/Ti/SiO2/Si(100) substrates. The yttrium concentration, x, was varied from 1.5 to 3.5 wt% by 0.5 wt%. The annealing temperature and time of the thin films are 550–650°C for 5–10 min in 100% O2 atmosphere. The influence of the yttrium contents on the ferroelectric properties of PZT thin films has been studied. We investigated the imprint properties of Y-doped PZT (40/60) thin films at bias voltage and a temperature of 120°C. It is found that the imprint- resistant properties of the PZT thin films are enhanced by a suitable Y dopant concentration.

DIELECTRIC AND PIEZOELECTRIC PROPERTIES OF Mn DOPED (K, Na)0.96Sr0.02NbO3 CERAMICS

ABSTRACT Dense lead free ceramics with composition of (K0.5Na0.5)0.96Sr0.02Nb1-x MnxO3 (x = 0,0.01,0.02,0.03,0.04) were successfully prepared by conventional mixed oxide method, and their dielectric and piezoelectric properties have been investigated. The X-ray diffraction patterns indicated phase transition from peroveskite structure with orthorhombic symmetry to pseudo-tetragonal symmetry with increasing Mn content. Low loss tangent and relative high planar electromechanical coupling factor were obtained at x = 0.02 by the introduction of Sr and Mnion. The main parameters for the composition of x = 0.02 are: ϵ33 T/ϵ0 = 479, d33 = 121 kp = 41%, Qm = 298, tanδ = 1.6%, Tc = 391°C. The rates of resonant frequency variation, αfr, and planar coupling factor variation, αkp, with temperature 80°C are −1.85% and +1.19%, respectively. This material may be suitable for applications in ultrasonic transducers.

EPITAXIAL GROWTH OF PLZT THIN FILM ON SrTiO3 SUBSTRATE BY SPUTTERING METHOD

ABSTRACT PLZT thin films were prepared on SrTiO3 substrate by RF magnetron sputtering method. The electrical measurements were conducted on PLZT films in metal-ferroelectric-semiconductor capacitor configuration (MFS). The PLZT thin films annealed at 650°C showed well-saturated hysteresis loops with remanent polarization and coercive electric field values were 0.3 μ C/cm2 and 36 KV/cm respectively. The relationship between the orientation of thin film and thermal treating condition was discussed. The PLZT thin films with a thickness of 1.5 um were epitaxially grown on SrTiO3 substrate successfully.

STUDY ON DIELECTRIC AND FERROELECTRIC ANISOTROPY FOR HOT-FORGED PZN-PLZT CERAMICS

ABSTRACT Dielectric and ferroelectric properties of Pb0.88La0.12(Zn1/3Nb2/3)0.3(Zr0.4Ti0.6)0.67O3 ceramics prepared by hot forging method and conventional sintering have been studied. For temperature dependence, the maximum value of dielectric loss measured in the direction perpendicular to the pressing axis was 7 times higher than that measured in the parellel direction and a more broadened dielectric permittivity peak was also observed in the perpendicular direction. Taking into account the fact that no obvious grain orientation was evidenced from the XRD patterns of the compared samples, this anisotropy in dielectric property was attributed to difference in the distribution of stresses and defects in the parallel and perpendicular direction.