Wenjian Leng

Structural and optical properties of BaxSr1−xTiO3 thin films on indium tin oxide/quartz substrates prepared by radio-frequency magnetron sputtering

BaxSr1−xTiO3 (x=0.6 and 0.8) thin films have been prepared on indium-doped tin oxide (ITO) coated quartz substrates using radio-frequency magnetron sputtering. Their structural properties and surface morphologies were examined by x-ray diffraction and atomic force microscopy, respectively. The BaxSr1−xTiO3 (BST) thin films with x=0.6 and 0.8 annealed at 650°C for 20min exhibit good surface morphology and well-crystallized perovskite structure. High quality BST ferroelectric thin films were further investigated by electrical measurements, showing the remnant polarization (Pr) of 6.75μC∕cm2 and the coercive field (Ec) of 43.2kV∕cm. Optical transmittance measurement indicated that the Ba concentration has an effect on the band gap energy (Eg) structure of the BaxSr1−xTiO3 thin films. The Eg decreases linearly with the increase of the Ba content. The refractive index (n) and extinction coefficient (k) of the BST films with x=0.6 and 0.8 were obtained by fitting the spectroscopic ellipsometric data using a par...

Structure-related optical properties of (Pb,La)(Zr,Ti)O3 thin films on indium tin oxide∕quartz substrates

To be suitable for integrated optical devices, (Pb,La)(Zr,Ti)O3 (PLZT) ferroelectric thin films require high crystalline quality, low surface roughness, high optical index, and high transparency. In this paper, PLZT thin films have been grown in situ on indium tin oxide (ITO) coated quartz substrates by rf magnetron sputtering. X-ray diffraction, scanning electron microscopy (SEM), and atomic force microscopy (AFM) were used to investigate the structural properties of these PLZT films. The results show that the ferroelectric films exhibit satisfying crystallization with the highly (110)-oriented growth from 550°C, and the surface roughness value (∼3.1nm) in studied films is within the optimum range so that a low optical loss can be obtained. High quality PLZT ferroelectric thin films were further investigated by electrical measurements, showing that the remnant polarization Pr and coercive field Ec are approximately 11.3μC∕cm2 and 56.2kV∕cm, respectively. Spectroscopic ellipsometry (SE) was employed to ch...

Linear and nonlinear optical properties of (Pb,La)(Zr,Ti)O3 ferroelectric thin films grown by radio-frequency magnetron sputtering

Linear and nonlinear optical properties of lanthanum-modified lead zirconate titanate ( Pb0.92La0.08)( Zr0.65Ti0.35) O-3 ( PLZT 8/65/35) ferroelectric thin films are presented in this paper. The PLZT ferroelectric thin films were grown on quartz substrates by radio-frequency magnetron sputtering at 650 degrees C. Their crystalline structure and surface morphologies were examined by x-ray diffraction and atomic force microscopy, respectively. It was found that the PLZT thin films exhibit well-crystallized perovskite structure and good surface morphology. The fundamental optical constants ( the band gap energy, linear refractive index and absorption coefficient) were obtained through the optical transmittance measurements. A Z-scan technique was used to investigate the optical nonlinearity of the PLZT thin films on quartz substrates. The films display a strong third-order nonlinear optical effect. A large and negative nonlinear refractive index n(2) is determined to be 1.21 x 10(-6) esu for the PLZT thin films. All results show that the PLZT ferroelectric thin films have potential applications in nonlinear optical devices.

Large third-order optical nonlinearity in (Pb, La)(Zr,Ti)O3 ferroelectric thin film

Ferroelectric (Pb0.92La0.08)(Zr0.65Ti0.35)O3 (PLZT) film with good surface morphology and perovskite structure was grown in situ on quartz substrate by radio-frequency magnetron sputtering at 650°C. The fundamental optical constants (the band gap energy, linear refractive index, and absorption coefficient) of the film are obtained by optical transmittance measurement. The third-order nonlinear optical properties of the films were investigated by the Z-scan technique. The magnitude and sign of the nonlinear refractive index n2 were determined, as was the negative sign, which indicated a self-defocusing optical nonlinearity. A large nonlinear refractive index as high as 1.21×10−6esu is displayed in the film. All results show that PLZT ferroelectric thin film has potential applications in nonlinear optical devices.

Electrical and optical properties of lanthanum-modified lead zirconate titanate thin films by radio-frequency magnetron sputtering

(Pb,La)(Zr,Ti)O-3 (PLZT) thin films were grown on Pt/Ti/SiO2/Si and fused quartz substrates by radio-frequency magnetron sputtering at 650 degrees C. X-ray diffraction analysis shows that the PLZT films are polycrystalline with (100)-preferential orientation. The Al/PLZT/Pt capacitors have been fabricated and show good ferroelectric properties with the remanent polarization of 24.3 mu C/cm(2) and coercive field of 142 kV/cm. The leakage current density is only about 0.86x10(-7) A/cm(2) at 200 kV/cm. The energy gap E-g of the films is estimated to be about 3.54 eV by optical transmittance measurements. Their fundamental optical constants are obtained by a Filmetrics F20 reflectance spectrometer (F20). These results show that the PLZT ferroelectric thin films are promising materials for optoelectronic devices. (c) 2006 American Institute of Physics.

Nonlinear optical properties of the lanthanum-modified lead zirconate titanate ferroelectric thin films using Z-scan technique

Lanthanum-modified lead zirconate titanate (Pb,La)(Zr,Ti)O3 (PLZT) ferroelectric thin films with perovskite structure were fabricated on quartz substrates by rf magnetron sputtering at 650 °C. Their optical fundamental constants (the band gap, linear refractive index, and absorption coefficient) were obtained through optical transmittance measurements with the envelope method. The nonlinear optical properties of the PLZT films were investigated by the Z-scan technique. The films display strong nonlinear optical effects. A negative nonlinear refractive index n2 is determined to be 1.21×10-6 esu in the films. These results show that the PLZT ferroelectric thin films are promising materials for nonlinear optics.

MICROWAVE-INDUCED NANOCRYSTAL LINES ON THE Ba0.6Sr0.4TiO3 THIN FILMS SURFACE

ABSTRACT Ba0.6Sr0.4TiO3 (BST) thin films were deposited on Pt/Ti/SiO2/Si (100) substrates by radio-frequency magnetron sputtering. Nanocrystal lines on the BST films surface were obtained by microwave electrical field irradiation annealing. Atomic force microscopy (AFM) results reveal that microwave annealing can give rise to certain self-assembled nanocrystal lines on the BST films surface, and the length and the width of the nanocrystal lines are dependent on annealing time. After the films further annealed for 20 min or more, the nanocrystal lines broke up into spherical nanocrystals of about 25 nm in diameter. The directions of BST nanocrystal lines are determined by microwave electrical field. X-ray diffraction (XRD) shows that the microwave-annealed BST films are (110) preferred orientation. Specular X-ray reflectivity (XRR) measurement shows that the surfaces of the microwave-annealed BST thin films exhibit anisotropy.

An Analytic Theory of Dielectric and Optic Nonlinear Effects of Ferroelectrics

An analytical theory of dielectric and optic non-linear effects of ferroelectrics is presented in this paper. The theory includes the intrinsic relations between the ferroelectricity (P-E), dielectric nonlinear (ε-E) and optic nonlinear (△n-E) in ferroelectric materials. An analytic equation for dielectric and optic nonlinear effects of ferroelectrics is obtained, and then the simple polynomial functions of P(E), ε(E) and △n(E) are used to describe the mechanism of dielectric and optic nonlinearity. From the experimental hysteresis loop, e.g., ε-E and △n-E curves in ferroelectric materials, the boundary conditions and original conditions are obtained, and the related coefficients are also determined in the terms of P<inf>m</inf>, P<inf>s</inf>, P<inf>r</inf>, E<inf>A</inf>E<inf>c</inf>, and E<inf>D</inf>. Moreover, this analytic theory is verified by the data from Ba<inf>0.9</inf>Sr<inf>0.1</inf>TiO<inf>3</inf>and PLT/PZT films.