The paper presents general information on LTCC materials, manufacturing processes and properties of fired modules. A Multichip Module package has been the main application of Low Temperature Cofired Ceramic (LTCC) technology. Recently, this technology is also used for production of sensors, actuators and microsystems. The research and development on the LTCC sensors and microsystems carried out in the Laboratory of Thick Film Microsystems at Wroclaw University of Technology are presented. LTCC microfluidic system is described in detail. Moreover, a short information is given on other LTCC applications .
Recently a new technology of piezoelectric transducers based on PZT thick film has been developed as a response to a call for devices working at higher frequencies suitable for production in large numbers at low cost. Eight PZT thick film based focused transducers with resonant frequency close to 40 MHz were fabricated and experimentally investigated. The PZT thick films were deposited on acoustically engineered ceramic substrates by pad printing. Considering high frequency and non-linear propagation it has been decided to evaluate the axial pressure field emitted (and reflected by thick metal plate) by each of concave transducer differing in radius of curvature - 11 mm, 12 mm, 15 mm, 16 mm.
All transducers were activated using AVTEC AVG-3A-PS transmitter and Ritec diplexer connected directly to Agilent 54641D oscilloscope. As anticipated, in all cases the focal distance was up to 10% closer to the transducer face than the one related to the curvature radius. Axial pressure distributions were also compared to the calculated ones (with the experimentally determined boundary conditions) using the angular spectrum method including nonlinear propagation in water. The computed results are in a very good agreement with the experimental ones. The transducers were excited with Golay coded sequences at 35-40 MHz. Introducing the coded excitation allowed replacing the short-burst transmission at 20 MHz with the same peak amplitude pressure, but with almost double center frequency, resulting in considerably better axial resolution. The thick films exhibited at least 30% bandwidth broadening comparing to the standard PZ 27 transducer, resulting in an increase in matching filtering output by a factor of 1.4-1.5 and finally resulting in a SNR gain of the same order.
Graphene is a very promising material for potential applications in many fields. Since manufacturing technologies of graphene are still at the developing stage, low-frequency noise measurements as a tool for evaluating their quality is proposed. In this work, noise properties of polymer thick-film resistors with graphene nano-platelets as a functional phase are reported. The measurements were carried out in room temperature. 1/f noise caused by resistance fluctuations has been found to be the main component in the specimens. The parameter values describing noise intensity of the polymer thick-film specimens have been calculated and compared with the values obtained for other thick-film resistors and layers used in microelectronics. The studied polymer thick-film specimens exhibit rather poor noise properties, especially for the layers with a low content of the functional phase.
LTCC-based pressure sensors are promising candidates for wet-wet applications in which the effect of the surrounding media on the sensor's characteristics is of key importance. The effect of humidity on the sensor's stability can be a problem, particularly in the case of capacitive sensors. A differential mode of operation can be a good solution, but manufacturing the appropriate sensing capacitors remains a major challenge. In the case of piezoresistive sensors the influence of humidity is less critical, but it still should be considered as an important parameter when designing sensors for low-pressure ranges. In this paper we discuss the stability of the sensors' offset characteristics, which was inspected closely using experimental and numerical analyses.
Studies of electrical properties, including noise properties, of thick-film resistors prepared from various resistive and conductive materials on LTCC substrates have been described. Experiments have been carried out in the temperature range from 300 K up to 650 K using two methods, i.e. measuring (i) spectra of voltage fluctuations observed on the studied samples and (ii) the current noise index by a standard meter, both at constant temperature and during a temperature sweep with a slow rate. The 1/f noise component caused by resistance fluctuations occurred to be dominant in the entire range of temperature. The dependence of the noise intensity on temperature revealed that a temperature change from 300 K to 650 K causes a rise in magnitude of the noise intensity approximately one order of magnitude. Using the experimental data, the parameters describing noise properties of the used materials have been calculated and compared to the properties of other previously studied thick-film materials.
Semiconductive - resistive sensors of toxic and explosive gases were fabricated from nanograins of SnO2 using thick-.lm technology. Sensitivity, selectivityand stabilityof sensors working in di.erent temperature depend on the way the tin dioxide and additives were prepared. A construction also plays an important role. The paper presents an attitude towards the evaluation of transport of electrical charges in semiconductive grain layer of SnO2, when dangerous gases appear in the surrounding atmosphere.
This paper presents the concept and modern technological approach to the fabrication of discrete, integrated and integral micropassives. The role of these components in modern electronic circuits is discussed too. The material, technological and constructional solutions and their relation with electrical and stability properties are analyzed in details for linear and nonlinear microresistors made and characterized at the Faculty of Microsystem Technology, Wrocław University of Technology.
Numerous films, especially reinterpretations of the Gospel, can be read as loci theologici. Nevertheless, it’s important to recognize that the commercially motivated interest of filmmakers has its theological consequences: a resulting challenge is the catechetical use of apocryphal films in the pastoral praxis of the Church. The paper recalls main documents of the Church, relating to the cinema, stressing the absence of official teaching on the cinema in the last 20 years. Films, produced with commercial motivation, are often kitsch; it’s a result of tendencies to gain the possibly large audiences and to fulfill their expectations. An analysis of selected films (e.g. The Passion of the Christ and Son of God) indicates that the kitschy audiovisual apocrypha, superficial, emotional and lacking of authenticity, become a false filmic transformation of the message of the Bible. The paper postulates the need of constructing a theology of film: its object could be audiovisual texts, which extra-ecclesial theologies influence religious imagination and thinking of the viewers.
The aim of this work was to produce a thin SnO2 film by a technique combining the sol-gel method and electrospinning from a solution based on polyvinylpyrrolidone and a tin chloride pentahydrate as a precursor. The spinning solution was subjected to an electrospinning process, and then the obtained nanofiber mats were calcined for 10 h at 500°C. Then, the scanning electron microscopy morphology analysis and chemical composition analysis by X-ray microanalysis of the manufactured thin film was performed. It was shown that an amorphous-crystalline layer formed by the SnO2 nanofiber network was obtained. Based on the UV-Vis spectrum, the width of the energy gap of the obtained layer was determined.
Thin films of crystallized LaCoO3 were grown on Si substrate by Pulsed Laser Deposition at different temperatures (750°C, 850°C and 1000°C). The structural characterization of the LaCoO3 thin films was done by combining several techniques: Scanning Electron Microscopy (SEM), Atomic Force Microscope (AFM), Transmission Electron Microscopy (TEM) and Grazing Incidence X-Ray Diffraction (GIXRD). The thin films crystallized in the expected rhombohedral phase whatever the deposition temperature, with an increase of crystallite size from 70 nm at 750°C to 100 nm at 1000°C, and an average thickness of the thin films of less than 200 nm. At 850°C and 1000°C, the thin films are crack-free, and with a lower number of droplets than the film deposited at 750°C. The grains of LaCoO3 film deposited at 850°C are columnar, with a triangular termination. At 1000°C, an intermediate layer of La2Si2O7 was observed, indicating diffusion of Si into the deposited film.
The paper presents the idea to improve the performance of thin film photovoltaic cells by a light capture enhancement through the introduction of down shifting energy converters. Luminescent down shifting layers convert high-energy photons (UV light) into low-energy ones (visible light), which are more efficient in a photovoltaic conversion. For this purpose, the application of a thin layer composed of zinc oxide (ZnO) nanoparticles deposited onto a thin film solar cell is proposed. The paper presents both experimental and theoretical results of this approach. Conducted investigations include an analysis of ZnO nanoparticle layers, deposited in two independent technology methods. The results showed that ZnO nanoparticles have a great potential of application as down converting layers and can be implemented to improve the efficiency of photovoltaic cells, especially in the field of thin film PV structures. The proposed new deposition method can potentially be used in some industrial photovoltaic applications.
In this paper an analysis of the surface properties of (Ti,Pd,Eu)Ox thin films prepared by magnetron sputtering has been described. In particular, the results of composition and structure investigations were studied in relation to the surface state and optical properties. It was found that (Ti,Pd,Eu)Ox film was nanocrystalline and had a rutile structure. The average crystallites size was equal to 7.8 nm. Films were homogeneous and had densely packed grains. Investigation of the surface properties by XPS showed that titanium was present at 4+ state (in the TiO2form), palladium occurred as PdO2(also at 4+ state), while europium was in Eu2O3form (at 3+ state). In comparison with the unmodiffied TiO2, the coating with Pd and Eu additives had a rather high transparency (approx. 47%) in the visible light range, its optical absorption edge was shifted towards into the longer wavelengths (from 345 nm to 452 nm), and the width of optical energy gap Egopt was nearly twice lower (1.82 eV). Besides, the resistivity of (Ti,Pd,Eu)Ox at room temperature was 1×103 Wcm. In the case of the film as-deposited on Si substrate (p-type) the generation of photocurrent as a response to light beam excitation (λexc = 527 nm) was observed.
ZnO thin layers were deposited on p-type silicon substrates by the sol-gel spin-coating method and, then, annealed at various temperatures in the range of 573–873 K. Photoluminescence was carried out in the temperature range of 20–300 K. All samples showed two dominant peaks that have UV emissions from 300 nm to 400 nm and visible emissions from 400 nm to 800 nm. Influence of temperature on morphology and chemical composition of fabricated thin layers was examined by XRD, SEM, FTIR, and Raman spectroscopy. These measurements indicate that ZnO structure is obtained for samples annealed at temperatures above 573 K. It means that below this temperature, the obtained thin films are not pure zinc oxide. Thus, annealing temperature significantly affected crystallinity of the thin films.