摘要:

Thin film PZT ferroelectrics have been fabricated in Canada since 1976 by magnetron sputtering and more recently by acetate-based sol gel processing and are now being considered for implementation into commercial communications systems. Processing based on rapid thermal annealing has shown marked advantages for crystallization into the required perovskite phase. Applications based on the piezoelectric properties of PZT films are shown to have an interesting potential for a range of devices.

ISSN:1058-4587    

DOI:10.1080/10584589208215708

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Recent developments in ferroelectric thin film deposition involving plasma based approaches, are described, which include a) multi-magnetron sputter deposition, b) Multi-ion-beam reactive sputter (MIBERS) deposition, c) Pulsed excimer laser ablation and d) ECR (Electron cyclotron resonance) plasma assisted deposition. These methods commonly prevailed intrinsic low energy ion bombardment during the growth process, which may be used for the control over composition, crystallization temperature and microstructure. A low energy (60–75 eV) ion bombardment of the ferroelectric Pb(Zr, Ti)O3thin films indicated a reduction in the phase formation/crystallization temperature, improved the electrical properties, microstructure and the surface smoothness. Discussion is presented exphasizing the effects of low energy bombardment in different deposition processes. Recent findings using rapid thermal annealing process are also described.

ISSN:1058-4587    

DOI:10.1080/10584589208215709

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Highly oriented, dense, and crack-free ferroelectric and paraelectric thin-films on three inch diameter Pt/Ti/Si3N4/Si (100) substrates were obtained by polymeric sol-gel processing. Ferroelectric PZT thin-films were fabricated at temperatures as low as 550°C within 15 minutes by rapid thermal annealing. The films heat treated at 700°C for 5 minutes were single grain thick and exhibited Pr, Psp, and Ecin the ranges of 29–32 μC/cm2, 44–53 μC/cm2, and 50–60 kV/cm, respectively, and high speed switching times below 5 ns on 30×30 μm2electrodes. A switching time of 2.7 ns was observed on 19×19 μm2area electrodes at a field of 200 kV/cm. Results of low and high field characterization on paraelectric PLT thin-films which were conventionally heat treated indicated that it has an excellent potential for use in ULSI DRAMs and as decoupling capacitors. These films showed a high charge storage density (15 μC/cm2) and a low leakage current (0.5 μA/cm2) at a field of 200 kV/cm. Also, the charging time for a capacitor area of 1 μm2at 200 kV/cm was estimated to be 0.10 ns.

ISSN:1058-4587    

DOI:10.1080/10584589208215710

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The remanent polarization (2Pr) of thin-film PZT capacitors was examined using a voltage pulse method. The amount of polarization remaining after a “write” pulse was found to be a function of both the time between the write and read pulses and the duration of the write pulse. The 2Prwas found to decrease significantly from 3 μs to 100 ms after the initial write. In some cases the remanent polarization decayed by almost 70 percent in this time regime. The fast decay component of 2Prwas also observed to be dependent on the duration of the write pulse (the write, pulse width). The longer the write pulse was applied the smaller the fast decay component became, leaving more measurable charge retained after 100 ms.

ISSN:1058-4587    

DOI:10.1080/10584589208215711

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Using a combination of pulsed laser deposition and sol-gel processing, we have fabricated epitaxial PbZr0.2Ti0.8O3/YBa2Cu3O7-x heterostructures on single crystalline [001] LaAlO3. Rutherford back-scattering studies show the composition to be the same as the nominal starting composition. Transmission electron microscopy shows the existence of a randomly oriented polycrystalline microstructure in the PZT layer with a grain size of about 500–1000Å. Microscopic pores were also observed in the PZT layer. The PZT film exhibits ferroelectric hysteresis with a saturation polarization of 22–25μC/cm2(at 7.5V, 1kHz), a remanence of 5–6μC/cm2and a coercive field of about 40kV/cm.

ISSN:1058-4587    

DOI:10.1080/10584589208215712

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

In this paper we describe recent successes of growth of epitaxial bismuth titanate (BTO) films by pulsed laser deposition (PLD) suitable for electro-optic and electrical switching device structures, and fabrication of an improved gate structure for a ferroelectric memory FET (FEMFET). TEM and x-ray results indicate that excellent crystalline quality BTO films were achieved on LaAlO3. Polarization switching was demonstrated for BTO capacitors with epitaxial superconducting YBa2Cu3O7as the lower electrode. Using an SiO2buffer layer, a BTO/Si structure was fabricated and direct charge modulation in the Si by polarization reversal in the BTO was demonstrated.

ISSN:1058-4587    

DOI:10.1080/10584589208215713

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

A modification of the conventional pulsed laser deposition technique was employed, whereby a low energy electron emitting filament was placed between the target and the substrate (-20 V filament/substrate bias) in order to produce reactive species (O2-and O−) during deposition. Using this modification, epitaxial thin films of PbZrxTi1−xO3 (PZT, 0 ≤ × ≤ 0.6) were preparedin situon virgin (100) MgO and (100) Pt/(100) MgO substrates at a substrate temperature of 550°C and in an oxygen ambient (0.3 Torr). The topography of films prepared without a filament on virgin MgO were porous and composed of grains of about 1000 Å in diameter. As the emission current was increased from 0 to 400 μA, the grain size decreased to less than 100 Å with a concomitant decrease in the porosity. The nucleation of crystallites of other orientations was observed at emission currents greater than about 500 μA. Trilayer structures (Pt/PZT/Pt/<100>MgO) were fabricated for electrical measurements. Non-filament-assisted PZT cells usually failed because of a high probability of conductive paths through the PZT layer. Filament-assisted films were much less prone to this problem. Typical remanent polarizations and coercive fields were 15–20 μC/cm2and 30–50 kV/cm, respectively.

ISSN:1058-4587    

DOI:10.1080/10584589208215714

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Ferroelectric thin films of BaTiO3and lead zirconate titanate, PbZr0.53Ti0.47O3(PZT), have been prepared by pulsed excimer laser deposition. The microstructure and crystallography of these films have been studied by scanning electron microscopy (SEM), energy dispersive x-ray spectrometry (EDX), transmission electron microscopy (TEM), x-ray diffraction (XRD), and differential scanning calorimetry (DSC). Electrical properties, including remanent polarization, dielectric loss, and dielectric constant, have been measured. Also, switched remanent polarization has been measured under conditions of continuous cycling.

ISSN:1058-4587    

DOI:10.1080/10584589208215715

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Pulsed UV excimer laser ablation was employed to deposit multi-axial, bi-axial and uni-axial ferroelectric compositions of PZT, bismuth titanate and lead germanate respectively. In general, a fluence lower than 2 J/cm2caused a preferential evaporation of volatile components, resulting in stoichiometric imbalance. However, the fluences beyond 2 J/cm2enabled the deposition of stoichiometric thin films of multi-component oxide systems. The intrinsic bombardment due to the energetic ablated species during the thin film deposition seemed to influence the composition, structure, orientation and the electrical properties. The electrical characterization of ferroelectric films indicated a dielectric constant of 800–1000, a Prof 32μC/cm2and Ecof 130KV/cm for polycrystalline PZT films and the corresponding quantities were measured to be 150, 7 μC/cm2and 20 KV/cm forin-situcrystallizedc-axis preferred oriented bismuth titanate films. Lead germanate thin films oriented alongc-axis (003) showed a dielectric constant of 30, a Prof 2.5 μC/cm2and Ecof 55 KV/cm.

ISSN:1058-4587    

DOI:10.1080/10584589208215716

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Studies of electrical properties and an equivalent circuit model is developed for ferroelectric PZT(Ti = 60%) thin film capacitors made by sol-gel spin coating with Pt electrodes. The equivalent circuit consists of two major parts: serial space charge capacitors demonstrating surface effects and parallel elements modeling the inner polycrystalline ferroelectric regions. This model is based on device physics which can demonstrate both the measured capacitance voltage characteristics and hysteresis curves. From the model fit to the data, an estimate of the space charge concentration at the surface and inner grain boundary region of 57times;1020cm−3and 1×1018cm−3respectively is made. Further electrical characterizations such as pulse switching and polarization degradation (fatigue) have also been studied. Using the equivalent circuit, other characteristics such as the switching time can be studied showing its dependence on applied voltage and capacitor area. The applied voltage dependence of fatigue is shown via an empirical equation where the degradation rate is electric field activated.

ISSN:1058-4587    

DOI:10.1080/10584589208215717

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor