摘要:

A model of ferroelectric switching in thin films which also exhibit semiconducting properties is presented. The two principle assumptions upon which the model is based are (1) that the threshold field for reverse domain nucleation,Ecm, is much greater than the field required for domain wall motion,Ecm, and (2) that the electrode-film interface is modeled as a metal-semiconductor interface. A film thickness dependence of the coercive field is qualitatively predicted by the model. When applied to the experimentally determined thickness dependence of coercive field in lead-zirconate-titanate thin films, the model predicts a donor concentration,ND, of 1018cm−3and a space charge surface layer thickness,W, of 0.2 μm.

ISSN:1058-4587    

DOI:10.1080/10584589408018654

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

LiTaO3thin film from have been obtained by RF-magnetron sputtering from monocrystalline target. The films have been deposited on (111) silicon and platinum without substrate heating. The amorphous films were subsequently annealed in the electric field. The morphology, crystal structure and composition of the films were investigated by means of XRD, SEM and AES spectroscopies. The influence of the annealing treatment in the electric field on the morphology and crystal structure of films is significant. The films grown in this fashion are preferentially oriented with thec-axis perpendicular to the surface of substrates and stoichiometric.

ISSN:1058-4587    

DOI:10.1080/10584589408018655

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

We calculate the coercive field of thin ferroelectric films caused by the domain wall pinning by surface inhomogeneities. The Joanny-De Gennes formula is generalized to the elastic energy of the line of intersection of the domain wall with the surface of ferroelectrics. The coercive field induced by the pinning is shown to be inversely related to the film thickness and to have a magnitude of the order of that observed in experiments.

ISSN:1058-4587    

DOI:10.1080/10584589408018656

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Sputtered thin films of perovskite-structured ferroelectric Pb(Sc1/2, Ta11/2)O3, (PST), produced using near stoichiometric ratios of the constituent metals require a post-deposition anneal temperature of 900[ddot]C to promote crystallization of the films in the perovskite phase. In this paper, we report that modification of the metal targets, resulting in the inclusion of a large excess of Pb in the deposited films, forms perovskite structured PST at a much lower substrate temperature of 600[ddot]C. The results of the permittivity and dielectric measurements and transmission electron microscope studies carried out on a PST film deposited on MgO-sapphire substrate are presented in this paper.

ISSN:1058-4587    

DOI:10.1080/10584589408018657

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A static I-V measurement method for ferroelectric thin films is developed to distinguish the leakage current from the switching current. The initial polarization state and the exponential decay behavior of the switching current are considered in this method. The feasibility of this I-V measurement method is investigated by examining fatigue effects on sol-gel derived PZT thin films. Changes in polarization due to fatigue are correlated with the changes in the switching current and the leakage current.

ISSN:1058-4587    

DOI:10.1080/10584589408018658

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Sol-Gel derived PbTiO3films were prepared with a polar glass ceramic as the substrate. The crystallization was investigated by means of X-ray diffraction. A preferentialc-axis orientation in the film was observed. The grain size and the microstrain were determined by measuring the integrated width of the diffraction. The grain size increases with increasing firing temperature following an Arrhenius relation. The microstrain decreases with increasing firing temperature and it is much higher in the [001] direction than in the [100] direction.

ISSN:1058-4587    

DOI:10.1080/10584589408018659

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Thin lead zirconate-titanate (PZT) films withc-axis orientation have been grown on MgO(100) using the tripole magnetron sputtering system. This system makes it possible to sputter lead and zirconium-titanium alternately from one composite metal target. Lead concentration in the deposited films, estimated by X-ray microanalyzer, has a great influence on the crystal growth. At relatively short period of the lead sputtering cycle, the concentration increases proportionally with the transported amount to the substrate. At longer period it becomes saturated with perovskite structure due to a self-limiting process. Although a small amount of the lead deficiency affects the crystallinity and the orientation of the film, a further deficiency of lead results in the precipitation of a ZrO2phase.

ISSN:1058-4587    

DOI:10.1080/10584589408018660

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

We present a study of breakdown fields in BaxSr1−xTiO3ceramics as functions of thickness, temperature, applied voltage ramp rate, electrode material and cross-sectional area. The data show evidence of Zener-like breakdown mechanisms. The d.c. leakage currents at voltages below breakdown are dominated by tunneling injection and image forces at low voltages (≤3 V), Schottky behavior at intermediate voltagesVa(3 V ≤Va≤ 6 V; 150 kV/cm ≤E≤ 300 kV/cm), and Fowler-Nordheim tunneling at high voltages; it is shown that both the Schottky emission regime and the ultimate breakdown arise from inter-grain effects rather than the BST/electrode interface, in accord with the theory of Neumann and Arlt and of Waser and Klee. In contrast to PbZrxTi1−xO3(PZT), which displays avalanche breakdown and space-charge limited d.c. leakage currents at normal 5 V silicon IC voltages, BST exhibits Schottky-dominated leakage currents in this 5 V regime, and is dominated by Fowler-Nordheim tunneling in its breakdown regime (ca. 120 MV/m). The reason for these differences in two otherwise similar perovskite titanates is due, we believe, to the columnar grain structure in PZT thin films, where the grains extend from electrode to electrode; this eliminates Zener breakdown across grain boundaries in PZT films. But it permits large space charge currents along PZT grain boundaries. The role of double injection (of electrons and holes) is discussed, and comparisons are made with PZT leakage current characteristics.

ISSN:1058-4587    

DOI:10.1080/10584589408018661

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The current-voltage relationshipI(V) for several different ferroelectric thin films often exhibits an apparent negative differential resistivity. In the present paper we show that in lead zirconate-titanate (PZT) this is a spurious artifact arising from rapid (parametric) measurement techniques and that it disappears for d.c. measurements made with measuring times ≥300 s. However, in other ferroelectric materials (selected samples with unusually high trap densities) it appears to be a genuine effect characterized by anI= aV3current-voltage relationship at high current densities (≥100 nA/cm2),I(V) hysteresis above a “pseudo-breakdown voltage,” and distinctV2-to-V3cross-over threshold.

ISSN:1058-4587    

DOI:10.1080/10584589408018662

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Lead lanthanum zirconate titanate [PLZT(91/651/35)] thin films were fabricated by spin coating of the metallo-organic solutions onto ITO-coated Corning 7059 glass substrates and heat treated at 600[ddot]C for 2 hours with different heating schedules. Microstructure and perovskite phase content of the PLZT thin films were studied using X-ray diffraction analysis (XRD), optical microscope (OM) and scanning electron microscope (SEM). A typical microstructure of the PLZT(91/651/35) thin films prepared using sol-gel process consists of micrometer-scale (about 4–5 μm) circular perovskite grains surrounded nanometer-scale pyrochlore grains. Effects of heating schedule and atmosphere on the crystallization kinetics of the amorphous PLZT thin films were studied. Firing at higher heating rate increased the number of perovskite nuclei and decreased pyrochlore content in the films. Also, the film heat treated at higher heating rate had lower transmittance at visible light because the interface boundary and the grain boundary increased and acted as the light scattering source. The films heat treated in air and O2atmosphere have relatively higher perovskite phase content than the film heat treated in Pb atmosphere.

ISSN:1058-4587    

DOI:10.1080/10584589408018663

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor