Wei-Gen Luo

Determination of the optical properties of sol-gel-derived BaxSr1-xTiO3 thin film by spectroscopic ellipsometry

The optical properties of amorphous and polycrystalline BaxSr1-xTiO3 (BST) thin films fabricated on Si(100) substrates by a sol-gel spin-coating technique were investigated by spectroscopic ellipsometry (SE). The spectrum of the extinction coefficient k was obtained by using the refractive index and structure parameters determined by SE in the photon energy range of 2.1-5.2 eV. A four-phase fitting model was employed to describe the optical properties of the BST thin films; the spectra of their optical constants and the band gap energy Eg were determined by means of optimization. In addition, the refractive index dispersion data related to the short-range-order structure of the films agreed well with the single-oscillation energy model. The dependence of the refractive index, k and Eg on annealing temperature were analysed. The variation of optical band gap energy with composition was investigated by changing the content of barium in the films.

Preparation of PZT(53/47) thick films deposited by a dip-coating process

Crack-free polycrystalline PZT (PbZrTiO3) thick films up to 15 µm with perovskite structure have been prepared from a dip-coating process. The influence of substrate characteristics, withdrawal speed and ionic concentration of precursor solution on the morphology and microstructure of PZT film was examined. The dielectric, ferroelectric and piezoelectric properties of PZT thick films on Pt/Ti substrate were measured and evaluated. PZT(53/47) thick films on Pt/Ti substrate exhibits a excellent electric properties, e.g. Pr: 35 µC/cm2; Ec: 32 kV/cm; er: 830; tan δ: 0.01-0.03; d33: 142.

Preparation of PZT thick films by one-step firing sol-gel process

Abstract A one step firing process was used in preparing PZT(53/47) thick films to prevent the film cracking. Films with a single layer thickness over 0.6 μm have been prepared. XRD and SEM studies were carried out to verify the crystal growth mechanism in the firing process. The microstructures, crystallinity, ferroelectric and dielectric properties of the films were compared with those of the films prepared by the conventional sol-gel firing process. The influences of lead excess and film thickness on the film properties were also studied.

Spectroscopic Ellipsometry of BaxSr1—xTiO3 Thin Films Prepared by the Sol–Gel Method

Stoichiometric Ba x Sr 1-x TiO 3 (BST) thin films with various values of x were prepared on Si(100) substrates by the sol-gel method. The influence of Sr content on the structure and the optical properties was studied by X-ray diffraction (XRD) and spectroscopic ellipsometry (SE) in the UV-visible region. The measured SE spectra were analyzed with an appropriate procedure to accurately determine the thickness and the optical constants of thin films. It has been found that the optical constants of the BST films are functions of the film composition. The optical bandgap energy increases with the increasing of Sr content.

Optical properties of polycrystalline and amorphous thin films of Pb(ZrxTi1−x)O3 prepared by a modifed sol-gel technique

Abstract Pb(ZrxTi1−x)O3 (PZT, x=0, 0.8, 1) thin films on fused quartz and Pt-coated Si substrates were prepared by a modified sol-gel process. Without using reflux and distillation to remove water. Phase structure, refractive indices n of amorphous and polycrystalline PZT thin films were obtained by X-ray diffraction, spectroscopic ellipsometry, and UV-VIS spectroscopy. PbZrO3 thin films on fused quartz substrates annealed at various temperatures, the absorption edges shifted is mainly due to phase structure changed from amorphous to polycrystalline. The refractive indices n of crystalline PbZrO3 thin film on Pt-coated Si substrates, compared with that of crystalline thin films of PbTiO3 and PZT80/20 were discussed.

Influence of top electrode of PZT capacitor on ferroelectric properties

PZT thin films were prepared by a modified sol-gel technique. Au was used as a top electrode of PZT capacitor. An influence of the process of the top electrode on the PZT ferroelectric capacitor was investigated. The relationship between remnant polarization, coercive electric field and the conditions of thermal treatment for the top Au electrode was discussed. The diffusion of Au and the interface between PZT and Au were analyzed by Auger spectra too. The proper heat treatment condition for optimal ferroelectric performance in the PZT capacitor was suggested.

Preparation and properties of IrO2 thin films grown by dc magnetron reactive sputtering method

Iridium oxide (IrO2) thin films were successfully grown on SiO2/Si(100) substrate by DC magnetron reactive sputtering method with an Ir target (99.99% purity). The effects of sputtering parameters and annealing conditions on the crystalline nature and morphology of IrO2 thin films were discussed. High orientation at (110) or (200) of IrO2 thin films were occurred by annealed films. For fatigue properties, PZT thin films using an IrO2 electrode have largely improved than that using a Pt/Ti electrode.

The influence of Y-dopant on the properties of BST films derived from a sol-gel process

Abstract The optical and dielectric properties of Y-doped Ba0.7Sr0.3 TiO3 thin films were investigated. The strong correlation was observed between the dopant concentration and materials properties. The optical band gap energy decreases with Y-dopant in BST thin films, whereas there was an increase of the band gap energy as the Y-dopant concentration increases. The dielectric constant decreases when the Y-concentration increases from 1 to 10 mol%.

Preparation of PZT fine powders for fabricating PZT thick films

Abstract A new process for preparation of PZT fine powder was proposed. By adding acetone and ammonia water to the precursor solution at suitable stages, nanosized powders with minimum agglomeration can be obtained. The effect of these additives on the powder preparation is analyzed according to the principle of the growth dynamics and the agglomeration mechanism of powders. Uniform powders with a perfect perovskite-type PZT phase have been obtained and the size of the powder is in the range of 100–200nm. Pb(Zr.40Ti.60)O3 thick film with 10 μm thickness and excellent properties have been successfully prepared by mixing PZT powders into a PZT sol-gel solution to form a 0/3 ceramic-ceramic composition.

Preparation of PZT thick films by 0-3 composite method

PbZr0.40Ti0.60O3 (PZT) thick films are prepared on Pt/Ti/SiO2/Si substrate by a sol gel based 0 - 3 composite method. The influence of processing variable including powder characteristics, solvents feature and annealing condition is investigated. Microstructure and electric property of PZT thick films are examined and analyzed. Optimum parameters of process are suggested. PZT thick film of 10 micrometers thickness with excellent ferroelectric and dielectric properties has been obtained (Pr 24 (mu) C/cm2, (epsilon) r 680 at 1 kHz.