摘要:

Ferroelectric films of composition Pb1−xLax(ZryTi1−y)1−x/4)O3(x=0−0.07, y=0.4−0.6) have been prepared on Pt/Ti/SiO2/Si substrates using an alcohol based solgel process reacted at room temperature. FTIR, NMR, DTA, and SAXS measurements have been used to address the chemistry of the alkoxide-alcohol-water-acetylacetone system. Films having 10% lead excess, dried at 150°C, fired at 420°C and RTP processed (ramp rate 100°C/sec., 650°C for 60 sec.) crystallized in the perovskite phase and showed Ps, Prand Hcranging from 25–30μC/cm210–15 μC/cm2and 60–90 kV/cm, respectively. A model for variations in dielectric constant with porosity has been used to correlate these parameters with the solvent content of the sol.

ISSN:1058-4587    

DOI:10.1080/10584589508019359

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

We report chemical vapor deposition (CVD) of PbLaTiO3films for integrated pyroelectric devices. Pb(thd)2, La(thd)3and Ti(O-Pr)2(thd)2were introduced to the reactor via a single liquid precursor solution that is vaporized. Substrate temperatures were approximately 535°C and post deposition annealing was not used. Films were deposited on fused silica and Pt metallized Si substrates. The liquid delivery technique permitted excellent composition control and films on fused silica were predominantly [100] oriented with trace amounts of [110] and [111] present. Pyroelectricity for 0.7μm thick films deposited on Pt metallized Si was measured using a modified Byer-Roundi technique and pyroelectric coefficients as high as 90 nC/cm2·K were observed. The high crystalline quality and pyroelectric properties are attributed to the excellent composition control afforded by the liquid delivery CVD technique.

ISSN:1058-4587    

DOI:10.1080/10584589508019360

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Using (C2H5)3PbOCH2C(CH3)3(triethyl n-pentoxy lead : TEPOL) as a new Pb precursor, PbO, PbTiO3and PZT thin films were successfully grown by MOCVD. The main reaction for the growth of the PbO thin films was oxidation of TEPOL. PbTiO3thin films, whose dielectric constants ranged from 50 to 200, were grown at substrate temperatures higher than 525°C. Tetragonal and rhombohedral PZT thin films were successfully obtained at substrate temperatures higher than 470°C and 500°C, respectively - these temperatures being 50°C and 40°C lower than when Pb(C2H5)4was used as a Pb precursor. The PZT films obtained showed good dielectric and ferroelectric properties, and showed dielectric constants between 190 and 1000, remanent polarizations of 15–20 μC/cm2and coercive fields of 70–90 kV/cm. The toxicity of TEPOL was also discussed.

ISSN:1058-4587    

DOI:10.1080/10584589508019361

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

To deposit PZT (Pb(Zr,Ti)O3) thin films on Pt films sputtered on thermally oxidized silicon wafers, we used Pb(thd)2, Zr(thd)4, and Ti(iOC3H7)4as metal-organic chemical vapor deposition sources. The good composition control resulting form the use of Zr(thd)4provided in-depth uniformity near the interface between Pt and deposited PZT. This uniformity was revealed by TEM observations and in-depth composition analysis using EDX with subnanometer probing radius. PZT films 80 nm thick had a leakage current of 2 × 10−7A/cm2when the applied voltage was 1.5 V, and equivalent to a SiO2thickness of 0.4 nm. The variation of composition and thickness over a 4″ wafer was about 1%. This surface uniformity achieved by optimizing the source supply and pumping system, results in the electrical uniform PZT thin films required for fabricating large-scale memory devices.

ISSN:1058-4587    

DOI:10.1080/10584589508019362

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Studies performed by our group on composition-structure-property relationships of Pb(ZrxTi1−x)O3(PZT)-based heterostructure capacitors are reviewed. The work discussed is related to the synthesis and characterization of ferroelectric PZT and conductive Pt, RuO2, and La0.5Sr0.5CoO3layers and their integration into heterostructure capacitors suitable for non-volatile memories. The main objective of our research was to determine the influence of deposition parameters and layer processing on the composition, structure, and properties of PZT-based capacitors, with the goal of controlling fatigue, retention, and imprint effects. The work discussed relates mainly to the synthesis of films by ion beam sputter-deposition (IBSD) and pulsed laser ablation deposition (PLAD), where the heterostructures are grownin-situwithout exposing the interfaces to uncontrollable atmospheric conditions. Limited comparisons are presented between structural characteristics and properties of PZT capacitors produced by IBSD and PLAD and those synthesized by the sol-gel technique.

ISSN:1058-4587    

DOI:10.1080/10584589508019363

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The use of high-dielectric films for microwave devices, especially phased-array radar systems, in the tens of GHz regime requires very low-loss (0.01 to 0.1) films. Unfortunately most ferroelectrics have losses that diverge (greater than unity) in this frequency range. We develop in the present study quantitative models for dielectric loss in both SrTiO3and BaxSr1−xTiO3(BST) that give dependences upon temperature, frequency, and especially voltage or field. In pure strontium titanate we find that loss is intrinsic, with quality factor “Q” greater than 1000; and a dramatic voltage dependence of tan δ is observed to fit the C3/2(V) dependence upon capacitance predicted for three- and four-phonon anharmonicity for voltages up to 5V (E = 250 kV/cm). In most barium strontium titanate ceramic films the loss is extrinsic at 100 MHz, and the surface layer model of Neumann and Hofmann describes the dependence of tan δ upon thickness D rather well, with tan δ increasing from 0.001 at D = 5 microns to 0.10 at 50 nm. Typical values at 250 nm are ca. 0.015.

ISSN:1058-4587    

DOI:10.1080/10584589508019364

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

An economic and pollution-free technique for electroless chemical deposition of transparent and electrically conductive sub-micron films on the surfaces of glass, ceramics, transparent polyester films, metal, and ferroelectric thin films has been developed. The technique is based on hydrolytic decomposition of metal-thiosulfate or metal-selenosulfate complexes in aqueous solutions, and has been successfully used for deposition of transparent and electroconductive copper sulfide and copper selenide thin films of a variable composition. The basic optical and electrical characteristics of the as-deposited and annealed films are also reported.

ISSN:1058-4587    

DOI:10.1080/10584589508019365

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

After a short description of the structure and operation of a pyroelectric sensor, the thermal conditions of the sensing element, the thermal-to-electrical conversion and the signal processing of pyroelectric thin film sensors will be represented. By means of the complex normalised current responsivity TR(jω, s) and figures of merit Mv, M1and MD, an universal description of the sensor's internal operation is obtained. The influence of electrothermal coupling effects on the dielectric loss of the pyroelectric thin film is also discussed. Substantial requirements to the pyroelectric thin film and the sensor design are derived. A comparison of often used thin film ferroelectrics shows that the application of P(VDF/TrFE) in low cost sensors can be advantageous although the figures of merit are lower. Copolymer film can be easily deposited onto a silicon wafer in post-processing after read out circuit fabrication, for instance by spin coating of a copolymer solution. Furthermore, the very low thermal conductivity provides good thermal insulation between the pyroelectric film and readout circuitry. The chosen P(VDF/TrFE) with a molar content of 70 % VDF shows a spontaneous polarisation of 8 μCcm−2and a pyroelectric coefficient of 3.5 nCcm−2K−1, a dielectric constant of 8 and a dielectric loss of about 0.018 at 25 °C. By a computer simulation, an optimum sensor design was achieved for single-element sensors and linear arrays. The central feature is a self-supporting carrier membrane of Si3N4(about 150 nm) and SiO2(500 nm), processed by bottom side etching of silicone wafers covered with a spin coated P(VDF/TrFE) thin film of about (1…2) μm in thickness. A radiation sensitive area (1×1) mm2and (2×2) mm2was choosen for the single-element sensor. In the linear array 128 pixels are arranged with a pitch of 100 μm, the pixel area is (90×100) μ2. A CCD read out circuit with gate modulation input structure is used as multiplexer. The specific detectivity D* (500 K, 10 Hz) of the single-element sensor is 3·108cmHz½W−1. At a frequency of 40 Hz the linear array shows a NEP of 4.5 nW and a MTF of 0.32 at a spatial frequency of 3 lpmm−1.

ISSN:1058-4587    

DOI:10.1080/10584589508019366

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A dual element, point, infra-red detector is being developed from a solgel deposited PbTiO3thin-film on a micro-machined silicon substrate. Patterning of the ferroelectric film and the electrodes is accomplished by photolithographic techniques. Membranes to reduce the thermal conduction from the sensor elements are created in the underlying substrate by anisotropic etching of the silicon. The measured voltage responsivity (Rv) as a function of radiation modulation frequency is compared to theoretical predictions and to conventional pyroelectric detector characteristics. Optimisation of the performance with respect to the device design is discussed.

ISSN:1058-4587    

DOI:10.1080/10584589508019367

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A high performance pyroelectric infrared sensor array based on epitaxially grown Pt and La-modified PbTiO3(PLT) thin films is fabricated by RF magnetron sputtering and micromachining technology. A single detector element forms a ferroelectric thin film capacitor epitaxially grown on a single crystal MgO substrate. The heat loss and the noise level are minimized by etching the substrate that leads to reduced thermal mass. Micromachining technology is used to support the fragile MgO substrate membrane by coating polyimide on top of the detector elements. The sensor array is mounted on a dip-type package sealed by a Silicon filter with anti-reflection coating to transmit 8–10 μm wavelength infrared radiation from a human body. It shows a very high detectivity of 8.5 ×108cm·√Hz/W and it is primarily due to the highly c-axis oriented epitaxially grown PLT thin film capacitor with the minimized thermal mass.

ISSN:1058-4587    

DOI:10.1080/10584589508019368

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor