摘要:

PLZT solutions were prepared from the as-received acetate precursors by means of a simple mixing procedure which produced a stock solution of approximately 10% oxide solids. Films were fabricated via dip coating and heat treating at 700°C for two minutes per layer. As many as 150 layers were deposited with an automatic dip coating system. All of the resulting films were optically transparent and well crystallized in the perovskite phase. The films were evaluated with respect to dielectric and electrooptic properties. Shutter contrast ratios as high as 1000 to 1 were measured.

ISSN:1058-4587    

DOI:10.1080/10584589308216713

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A ferroelectric memory field-effect transistor (FEMFET) where a ferroelectric thin film is incorporated directly into the gate structure of the transistor is attractive, because it provides not only nonvolatility, but also nondestructive readout (NDRO). At Westinghouse, we are currently developing a FEMFET using thin film barium magnesium fluoride (BaMgF4), a ferroelectric material that was discovered in 1969, but was not fabricated in thin film form until 1989. The BaMgF4films are grown by evaporation in an ultrahigh vacuum (UHV) chamber on clean Si(100). The natural tendency of these films to grow with the ferroelectric a-axis in the Si(100) plane has been overcome to obtain more random orientation with larger reversible polarization perpendicular to the film. A capping layer (SiO2) has been found to be essential for process integrability of these BaMgF4films. Ti-W metallization produced only a slight reduction in the capacitance-voltage (C-V) memory window. Switching speed of these films has been measured to be 40 to 45 nanoseconds. The first FEMFET fabricated with BaMgF4has exhibited 18 Volt memory hysteresis window with better than 105on/off current ratio for 20 Volt programming.

ISSN:1058-4587    

DOI:10.1080/10584589308216714

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Dielectric breakdown has been studied in several materials intended for high-dielectric DRAMs (dynamic random access memories), emphasizing lead zirconate-titanate (PZT) and barium strontium titanate (BST) ceramics. In this paper we present our results on PZT. A second paper will deal with BST. In order to distinguish among impulse thermal breakdown, de thermal breakdown, and avalanche breakdown mechanisms, studies have been carried out as functions of temperature, electrode material and shape, frequency and duration of applied fields, and specimen size and shape. Notable in the results is the fact that maximum breakdown field varies directly with electrode work function but is uncorrelated with electrode thermal conductivity; this militates against a purely thermal breakdown interpretation and instead favors an avalanche mechanism in which the iniation step is impact ionization of Ti ions from electrons emitted from the electrodes, followed by thermal run-away. Thickness dependence also favors avalanche mechanisms, but dependence upon applied field ramp rate favors an impulse thermal mechanism. Taken altogether, the data indicate characteristics of mixed impulse-thermal and avalanche mechanisms: i.e., electron-initiation followed by thermal run-away.

ISSN:1058-4587    

DOI:10.1080/10584589308216715

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Following polarization reversal, the strength of photovoltaic currents from lead-based perovskite film capacitors shows a dependence on time. An initial photovoltaic current decays rapidly to an almost steady-state current, which then decays slowly. We use a nonswitching surface layer model to explain remanent-polarization-dependent photovoltaic outputs in terms of photocarrier-generated screening of an incompletely compensated depolarization field within the film bulk. The rapid decrease in the initial photovoltaic current (photovoltaic transient) is explained as resulting from a change in the potential distribution within the film. The initial distribution results when charges compensating polarization are confined to the electrodes; the final distribution results when compensating charges occupy defect states within the volume of the surface layers. The slow decay in the steady photovoltaic current is explained as the result of changes in the potential distribution resulting from a slow decay in the remanent polarization. The log time rate of decay of the photovoltaic current is then equal to that of the remanent polarization, its determination serves as a measure of the log time decay rate of remanent polarization.

ISSN:1058-4587    

DOI:10.1080/10584589308216716

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A new optical probe method was developed by using electro-optic and piezoelectric effects and a phase sensitive detection to determine the polarization of domains in ferroelectric thin films. Ferroelectric domains within a region smaller than 1 μm were detected in annealed VDF(65)/TrFE(35) copolymer thin films. The switching dynamics of these individual domains were also investigated by using this method.

ISSN:1058-4587    

DOI:10.1080/10584589308216717

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Low temperature fired ceramics based on alumina/glass added oxide ceramics have been developed and are being used by several companies as substrates for high density assembled modular packaging.1–3The features of low temperature fireable substrates are the cofireability with highly conductive metals such as Ag, Ag-Pd, or Cu, and the cofireability with other passive component materials for L, C, R and relatively low dielectric constant elements. But most of these substrates have the disadvantage that their thermal expansion coefficient is not perfectly compatible with Si or GaAs. This paper reports the results of a newly developed cordierite/glass based substrate employing Cu as the surface and internal conductors and having the freedom of tuning the thermal expansion coefficient by changing the composition. The ceramic composition with adjustable thermal expansion coefficient value of 3 to 7 ppm/°C can be manufactured and easily matched with the thermal expansion coefficient of Si or GaAs without a big change of electrical performance.

ISSN:1058-4587    

DOI:10.1080/10584589308216718

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The microstructure and preferred orientation of PZT films deposited by spin-coating techniques are shown to depend on the morphology of the Ti/Pt bottom electrode. Annealing of the as-deposited Ti/Pt electrodes results in the formation of hillocks. These hillocks serve as nucleation sites for perovskite formation and thus determine the microstructure and preferred orientation of the crystallized PZT films. The microstructure features are investigated by X-ray diffraction analyses and scanning and transmission electron microscopies.

ISSN:1058-4587    

DOI:10.1080/10584589308216719

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor