摘要:

We report on the low temperature process for depositing epitaxial LiNbO3(0001) thick films on sapphire (0001) substrates by radio-frequency magnetron sputtering. To obtain this objective, we have developed a multi-steps process. Structural studies carried out through x-ray Θ-2Θ and phi scans measurements revealed that the epitaxy is verified at a substrate temperature of 490°C whatever the film thickness. The crystalline properties and the surface morphologies are rather conserved in the multi-steps process of deposition. Optical prism coupling characterizations have been carried out to qualify the film and the interface between the film and the substrate. A discussion is proposed in relationship with transmission electron microscopy (TEM) analysis.

ISSN:1058-4587    

DOI:10.1080/10584580008215645

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

MFIS structures having excellent clear interfaces and well-crystallized ferroelectric layer were successfully fabricated by a newly developed ultra thin metal buffer layer process on SiO2/Si. We examined the effect of sputtered Zr or ZrO2ultra thin films as a buffer layer for PbxLa1−xTiO3(PLT) growth. TEM observation revealed that the buffer layer formation process in which Zr oxidized after the metal deposition had advantages to produce MFIS structures. This method is also superior for the crystallization and the control of the orientation of PLT thin film on amorphous SiO2. Especially, for buffer layer thicknesses below 10 nm, preferredc-axis oriented PLT thin films were grown. The I-V characteristics of MFIS-FET fabricated by the proposed method showed a clear memory window due to the remanent polarization of the ferroelectric thin film. This process is the most attractive candidate for realizing MFIS structure memory.

ISSN:1058-4587    

DOI:10.1080/10584580008215646

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The synthesis and characterization of lead cation-incorporated strontium bismuth tantalate ferroelectrics were investigated. Monophasic layered perovskites were successfully prepared, and the formation of solid solutions of lead-doped SrBi2Ta2O9was corroborated. The value of lattice parametercmonotonicly increased with an increase in the lead content. The sinterability of the formed powder was poor; however, adding excess bismuth oxide markedly facilitated the sintering process. After sintering, the specimens exhibited strong preferredc-axis orientation. The degree ofc-axis orientation significantly varied with the sintering temperature and the doping amount of lead species. SEM analysis indicated that the variation in the morphology of the grains was related to the degree ofc-axis preferred orientation. The lead-doped specimens exhibited ferroelectric properties with well saturated P-E loops. Both the remanent polarization and the coercive field increased with the doping amount of lead cations.

ISSN:1058-4587    

DOI:10.1080/10584580008215647

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

An outline is given of progress on Gbit ferroelectric memory cells over the past year, including botth e-beam direct writing and spontaneous self-patterning. The thickness limitations are finally understood to be 3 or 4 nm from experiments by Tybell et al. and the theory of Ghosez and Rabe. The effect of lateral area on coercive field is found from the experiments of Alexe et al. to be zero, in strong disagreement with the theory of Bratkovsky and Levanyuk. The confinement energy is also negligible, in complete disagreement with the work of Kohiki et al.

ISSN:1058-4587    

DOI:10.1080/10584580008215648

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

A new method for formation of large single grains as large as 40 μm in length of the sputter-deposited PZT(65/35) thin films has been developed in this research group. Crystallized PZT dots were used as a seed and the grains were laterally grown to form a square pattern on the Pt substrate. It turned out that the electrical characteristics of the single grained PZT thin films were much superior to those of the poly-grained PZT thin films. The leakage current was measured to be less than 8x10−8A/cm2, the breakdown field more than 1,240 kV/cm, the value of saturation polarization and remanent polarization as high as 42 μC/cm2, 30 μC/cm2, respectively. No degradation of the polarization properties was observed even after the 2×1011cycles at 1 MHz using a ± 10 V wave form in Pt/PZT/Pt structure. The accelerated retention test revealed that it takes more than 6×107years for the remanent polarization to be reduced down to 80% of the original value.

ISSN:1058-4587    

DOI:10.1080/10584580008215649

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Applying voltage between the conductive tip in atomic force microscopy (AFM) and bottom electrode through Pb(Zr, Ti)O3(PZT) films can cause switching of ferroelectric domains. Formation and imaging of ferroelectric domains in nanometer scale could be applied to develop the future ultrahigh-density memory device. Relevant issues, i.e. bit (induced ferroelectric domains) size dependence on applied voltage and pulse width, are discussed. The bit size showed a log-linear dependence on the pulse width and a linear dependence on the pulse voltage. Using the analysis of electric field distribution, the size of the induced bits under certain pulse voltage and width was estimated.

ISSN:1058-4587    

DOI:10.1080/10584580008215650

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Effects of Ar ion damage prior to the phase transformation from pyrochlore to perovskite structure of PZT thin films have been investigated. As the degree of damage increased by increasing the acceleration voltage in the ion mass doping system, the phase transformation temperature decreased such that the temperature could be lowered down to 550°C when the film was damaged at 15kV for 5 minutes. When the films were damaged prior to the heat treatment, the final grain size of the perovskite thin films became less than 300Å. The microstructure showed the granular type rather than columnar structure after ion damage treatment and annealing. It turned out that relatively high value of the remanent polarization (about 30 μC/cm2) as well as improvement of the fatigue characteristics to a large extent are closely related to the fine grain size of thus obtained PZT films.

ISSN:1058-4587    

DOI:10.1080/10584580008215651

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Nanocrystalline thin films of different relaxor materials, namely Pb(Sc0.5Ta0.5)O3(PST), Pb(Sc0.5Nb0.5)O3(PSN), Pb(Mg1/3Nb2/3)O3(PMN) have been produced by RF-sputtering to investigate whether it will affect their dielectric properties if their grain size is reduced to the dimensions known from their nanodomains. The XRD shows that the amorphous film crystallizes in pyrochlore structure at lower temperatures and short times. Annealing at higher temperatures and far longer time intervals leads to an increasing amount of perovskite phase with a grain size in the nanometer range. These results including dielectric measurements will be presented and discussed.

ISSN:1058-4587    

DOI:10.1080/10584580008215652

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

In this work, the microstructural defects in SrBi2Ta2O9(SBT) ferroelectric thin films were investigated at the atomic-scale by high-resolution transmission electron microscopy (HRTEM). A stacking fault with an extra inserted Bi-O plane normal to thec-axis was observed in SBT film with 10mol% excess bismuth prepared by metalorganic deposition. Edge dislocations with an average space about 3nm were observed at the small misorientation angle (8.2°) tilt grain boundary of SBT film with (001)-orientation prepared by pulsed laser deposition. The Burgers vectorbfor the edge dislocation was determined to be 1/2[110]α0, where α0is the parameter of SBT unit cell. Chemical compositions of grains and grain boundaries in SBT films annealed in forming gas at 450°C and 500°C for 60 minutes were analyzed by using energy dispersive spectra at the nano-scale. Effects of the microstructural defects and microchemistry of the grain boundaries on the leakage current of SBT films are briefly discussed.

ISSN:1058-4587    

DOI:10.1080/10584580008215653

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

A number of basic materials issues need to be solved to successfully realize the stacked ferroelectric capacitor cell concept, which is needed for FERAM with densities beyond about 1Mb. This paper discusses barrier materials selection and the role of bottom electrode microstructure for future PZT-based FERAM based on the stacked cell concept. Conventional methods for PZT texture control, employing Pt as a template layer, are less suited for stacked cell layouts, because of the poor diffusion barrier properties of Pt. Modification of the microstructure of RuO2bottom electrodes has allowed us to eliminate the effect of underlying layers on the texture of PZT. The advantages of this approach in view of increasing circuit density of PZT-based FERAMs are discussed.

ISSN:1058-4587    

DOI:10.1080/10584580008215654

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor