Chuanren Yang

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...

Model for dielectric nonlinearity of ferroelectrics

Dielectric nonlinearity is an important characteristic of ferroelectrics. Based on the characteristics of hysteresis loops and e-E curves in ferroelectric materials, a model for dielectric nonlinearity of ferroelectrics is established. It is verified by the data of barium strontium titanate thin films.

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...

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.