摘要:

Pb(Zr, Ti)O3(PZT) films with very thin PbTiO3(PT) buffer layers inserted between the film and the Si/SiO2/Ti/Pt substrate were prepared by radio-frequency (r.f.) magnetron sputtering. The effects of PT buffer layer to the PZT films phase formation, dielectric and ferroelectric properties was studied. By using the PT buffer layer, polycrystalline film without buffer layer changed to highly (100) or (111) oriented PZT films depending of the buffer layer preferred orientation. The buffer layer orientation was controlled by the growth temperature. Intermediate PT layers enhance the perovskite phase formation; the perovskite PZT films on PT buffer layer were obtained at annealing temperature as low as 450°C instead of 625°C without buffer layer.

ISSN:1058-4587    

DOI:10.1080/10584589908210136

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Rapid thermal annealing (RTA), conventional furnace annealing (CFA) and combined RTA and CFA annealing (RCA) were adopted for thermal treatment of lead lanthanum titanate (PLT) thin films. Through comparison of morphologies, dielectric and ferroelectric properties, current-voltage (I–V) and capacitance-voltage (C–V) characteristics as well as pyroelectric currents, the features of each thermal annealing process were discussed. Optimized thermal annealing process was proposed. PLT thin films prepared by RCA process have higher remanent polarization, flatI–Vcurve, sharper nonlinearity peaks ofC–Vcurve and larger pyroelectric current density.

ISSN:1058-4587    

DOI:10.1080/10584589908210137

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Asymmetric switching properties were measured and quantified in sol-gel derived PZT thin films. The hysteresis asymmetry is attributed to the presence of an internal bias field that has been correlated with the self-polarization during fabrication. Annealing the sample under a remanent polarization with the polarity opposite to that of self polarization can yield a partially compensated, completely canceled, or even a reversed internal bias, depending on the annealing temperature. Three dominant processes associated with charge trapping at elevated temperatures are clarified and correlated with the annealing effects. They are aging, de-aging, and the redistribution of trapped charges. A model using simplified domain configurations is proposed to explain the observed annealing effects on hysteresis asymmetry and switchable polarization.

ISSN:1058-4587    

DOI:10.1080/10584589908210138

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A mathematical model with a simple log-time dependence has been developed using a theoretical approach to describe the complicated depolarization effect (ΔP) observed in ferroelectric thin films. The model includes two driving forces responsible for ΔP. One is the depolarization field due to incomplete compensation of ferroelectric polarization at the interfaces. This leads to the polarity independent depolarization effect characterized by a symmetric ΔP. Another one is the internal bias which can be parallel or antiparallel to the applied field, leading to a polarity dependent or asymmetric ΔP. The model successfully predicts the changing ΔPwith time. Two important parameters are estimated by analyzing the results of the model. One is the internal bias field, responsible for asymmetric retention of polarization. Another one is the size of back switched domains. The values obtained are comparable to the field near the surface and the surface layer thickness predicted by earlier models. The model provides an excellent fit to experimental data for two different types of PZT films, and is expected to be generally applicable to all thin film ferroelectrics.

ISSN:1058-4587    

DOI:10.1080/10584589908210139

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Pb(Zr, Ti)O3(PZT) thin films were deposited on various Pt substrates using a Pb(Zr0.63, Ti0.37)O3and a Pb target by rf magnetron sputtering. The preferred orientation of PZT films was significantly influenced by a structure of Pt electrode. (100)-oriented PZT films grew on Pt/Ti/SiO2/Si substrate while (ill) PZT films formed on TiOx/Pt/SiO2/Si substrate. TiOx/Pt/Ti/SiO2/Si substrate structure favored growth of a mixed orientation of (100) and (111) PZT films. The preferred orientation could be explained using concepts of lattice matching and minimization of surface energy. Ferroelectric and fatigue characteristics were also investigated and their relationship with microstructure and electrode structure were discussed.

ISSN:1058-4587    

DOI:10.1080/10584589908210140

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

SrBi2(Ta,Nb)2O9ferroelectric thin film capacitors with RuO2electrodes were prepared for the first time by a full chemical route. Stable sols of SrBi2(Ta,Nb)2O9precursors were obtained from mixtures of niobium (tantalum) ethoxide, bismuth and strontium 2-ethylhexanoates. Ruthenium dioxide precursors was prepared by dissolving an aqueous solution of ruthenium nitrosylnitrate into 2-methoxyethanol. Capacitors were fabricated by sequential spin coating the precursors on silicon wafers according to the sequence Si/RuO2/SrBi2(Ta,Nb)2O9/RuO2. Fully crystallized crack-free materials were obtained by annealing at 700°C for 2 h. Hysteresis loops (3–10 V) are similar to those observed using platinum electrodes.

ISSN:1058-4587    

DOI:10.1080/10584589908210141

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Thin films of BaxSryTi1−x−yoxide where x+y <0.5 have been prepared by CVD on Pt coated substrates. Within the above composition space there exist compositions of BST which optimize the tradeoff between large capacitance per unit area and small dependence on applied DC voltage. Such films would be useful as on-chip capacitors where intermodulation distortion or harmonic distortion must be minimized. Capacitance densities > 15 fF/mum2and a2coefficients < 100ppm/(volt)2with low leakage and low loss have been obtained.

ISSN:1058-4587    

DOI:10.1080/10584589908210142

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The opportunity of using ferroelectric (Pb, La), (Zr, Ti)O3thin films has been extensively studied for making integrated optic devices since they are expected to have potential optical properties. The configurations of the optical waveguide and the metallic electrodes are considered as the basic elements in fabrication schemes. Design rules are given in this study for the analysis of three-dimensional structures using theoretical tools, i.e., the Effective Index Method and Beam Propagation Method. Definition of the optogeometrical parameters, i.e., film thickness, rib width and height, coupling length, is essential for enhancing waveguiding performances. The optimization has been proposed taking into account the actual advance of the etching technology. Results are reported for planar optical waveguides.

ISSN:1058-4587    

DOI:10.1080/10584589908210143

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A review of electronic structural data is given and an interface Schottky model has been developed. X-ray photoemission spectroscopy (XPS) and secondary electron emission data have been used to determine the electron affinity of SBT and the band match-up for the SBT/Pt junction. The results of X-ray absorption spectroscopy studies and XPS valence band measurements indicated the electronic states above and below the bandgap of SBT. These experimental data have been compared with the results of tight-binding calculations. Angle dependent XPS measurements indicated that metallic bismuth is diffusing to the surface of SBT which would have significant influence on the electrical properties of the SBT/Pt junction. The hydrogen distribution in SBT, also an inportant issue for the device properties, has been probed using elastic recoil detection.

ISSN:1058-4587    

DOI:10.1080/10584589908210144

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Pb1.05−xLax(Ti1−x/4)O3(x = 0.00, 0.05, 0.1, 0.15, 0.20, 0.25 and 0.30) thin films were deposited on sapphire (0001) substrates by an acetic acid modified sol-gel technique. The films were characterized, using various techniques, in terms of their phase formation behavior, composition, microstructure and electrical characteristics. It was observed that the sol-gel derived films crystallize into the perovskite phase without any paraelectric cubic pyrochlore phase formation. For less than 15 at% lanthanum composition, the films show a tetragonal phase which transforms into a cubic phase for higher lanthanum content. The observed reduction of the tetragonal distortion with La addition is due to the pronounced shrinkage of the ‘c’ axis. X-ray photoelectron spectroscopy (XPS) was used to analyze the chemical composition. The XPS results are in excellent agreement with the nominal composition of the films. All films are extremely smooth, crack- and pinhole-free, and have a dense uniform microstructure. The grains are not single crystalline, instead each grain is the aggregate of numerous tiny perovskite crystallites. The apparent grain size increases with La addition. The values of dielectric constant, remnant polarization, saturation polarization and coercive field are comparable with the best reported values of sol-gel derived PLT thin films.

ISSN:1058-4587    

DOI:10.1080/10584589908210145

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor