Solid State Phenomena Vols. 97-98

Abstract: Modern sonar and radar measurement systems are widely used in the field of nondestructive testing for a long time. Usually reference signal is emitted towards the object to be investigated and we get a signal, which is the sum of reference signal reflected from different plies. The task of signal processing is to determine time instances corresponding positions of certain ply, which allow analyzing structure of object. Usually the cross correlation function (CCF) of transmitted sequence and received sequence is calculated. If peaks were clearly identified in the cross correlation function (CCF), it would be easy to determine time instances. Due to the noise some coherent peaks, additive to the expected peaks, appear on the CCF, which are confusing in regard to the clear distinction of target. In order to cancel effects of noise as much as possible some measures have to be taken for data manipulation noise cancellation, such as averaging, inverse filtering and so on. These signal-processing methods need a lot of floating point floating point operations and are time consuming. That is why the usage of such ultrasonic systems is limited in real time systems, which are the base for self-organizing systems. Amount of calculations depends on the length of reference signal, the length of reflected signal to be processed and the noise reduction method used in such system. A new system with reduced amount of calculations is considered in this article. In this system only parts of reflected signal corresponding peaks of CCF are processed. These parts are defined in acquisition mode and afterwards system enters measurement mode. New noise reduction method based on wavelet transforms coefficients thresholding is applied in this system. The length of reference signal impacts system noise immunity and amount of calculations. The main problem in ultrasonic non-destructive testing systems is to cancel out effects of the noise. The optimal length of reference signal for wavelet based signalprocessing method is defined. All these measures allowed significantly reduce amount of calculations in the self-organizing systems.

Abstract: Self-formation as a concept for irreversible evolution of the artificial object with complexity increase was introduced for understanding of the processes existing in microelectronics technology [1]. The concept of self-formation by itself was to some extend influenced by principles existing in biological world therefore from the very beginning there was an open question about limits of self-formation application: are we limited to the understanding of some technological processes or we can think about predicting new technological applications by applying selfformation concept. Recently developed tools for simulation of technological processes for Solar Cells manufacturing [2] clearly indicates that self-formation is becoming interesting tool for technologists trying to create and optimize microelectronic devices. The next step exploring selfformation application boundaries can be analysis of possibilities of the self-formation to demonstrate usual in biological life development and reproduction of the object. This presentation will be dedicated to the analysis of the conditions and possibilities by applying self-formation present self-formation, development and reproduction of artificial object.

Abstract: Eight-dimensional topological space providing an object evolution in time, including causes of evolution is presented. Part of Euclidean space separated by any close surface from complementary space, where any Euclidean point of space is juxtaposed with parameter, is being felt as an object. Coplanar approximation of flat planar devices is based on the flat, homogeneous, isotropic planar object and chaotic medium. The new, more general approximation of the topological space by equidistant surfaces, suitable for spatial planar objects, is presented. Selfformation of spatial objects (homogeneous, non-homogeneous, anisotropic), medium (chaotic, chaotic oriented, homogeneous oriented, structural) based on non-homeomorpheous mapping in peculiar points and evolution irreversibility, is discussed.

Abstract: The paper discussed the solar cells based on Cu-CdS contact assimilated to a heterojunction. Two methods were considered for our analysis: the rate equations approach and the stochastic equation one. The both permitted to obtain interesting information concerning the specific contact and are characterized by the order parameter.

Abstract: This report is devoted to the investigation of self-organized microrelief morphology control and optimization of the microrelief processing leading to obtain hotosensitivity of solar cells (SC) enhancement. The use of the heterostructures (HS) with the corrugated interface as active element allows one to increase SC photoresponse due to the front surface reflection reduction (optical losses). Surface barrier HS of Au/GaAs were used as model structures to reveal general relationship between the scattered light intensity and morphology peculiarities of HS interfaces.

Abstract: Relatively high cost of energy produced by solar cells prevents them from being used widely. One of the ways to address this problem is to create new, cost efficient solar cell production technologies. This presentation analyzes how, by applying self-formation principles it is possible to decrease number of photolithography processes used in high efficiency solar cell production, thus significantly reducing the cost of solar cell itself. All known planar technologies can be described based on self-formation principles; new microchip and integrated circuit technologies were created using self-formation as well. It is therefore natural to extend self-formation to solar cell technology. This presentation provides specific aspects of self-formation simulation as related to solar-cell technology. The object of the simulation is a cross-section of solar cell in two-dimensional Euclidean space and it.s evolution over time. Such kind of solar cell approximation simplifies the model, yet keeps all essential characteristics of the solar cell. The cross-section contains geometrical figures which approximate objects in the solar cell. Each figure is assigned with an integer parameter, approximating physical material. According to self-formation principles, evolution of each figure depends only on geometrical configuration of the figure itself, the parameter and interaction rules. Interaction rules define change of neighbouring points and approximate technological processes (etching, oxidation, coating etc). Combination of such processes enables construction of required solar cell configuration, with only minimum use of photolithography processes. Self-formation is simulated by two-dimensional 8-neighbour cellular automata based mechanism.

Abstract: Considering optimization of the technology and production of Solar Cells an overall goal is to lower the production costs per Watt through optimization of the parameters of Solar Cell. The dominant material up to now for the majority of commercially produced solar cells is crystalline silicon (c-Si). A lot of efforts has been undertaken to increase the electrical efficiency of Si based solar cells above 20% [3-5]. Unfortunately, efficiency improvements are often reached only with the help of costly process steps and as result without possibility to use such improvements in industrial products. One of the trends in achieving higher efficiency in monocristalline Si based Solar Cells is introduction of complicated spatial structure on absorbing surface of SC. Reports indicates expectations of efficiencies as high as 24% in laboratory samples but with significant raise in costs for Spatial SC production (Fig. 1). It is clear that optimization of technological steps and parameters must be considered thinking about introduction of Spatial SC. Optimization in the case of Spatial SC must be provided by two steps: first of all we need to evaluate impact of spatial structure to physical properties of the SSC and in the next step evaluate technological possibilities for production of the SSC with optimized physical characteristics.

Abstract: Battery powered mobile appliances have been booming for years. Examples include power tools, laptop computers and mobile phones. A photovoltaic power supply makes batterypowered appliances more practical for users, since the batteries don't go flat. The idea of a solar bag for PDAs and mobile phones was born to satisfy energy needs while traveling, hiking, climbing, sailing, cruising especially for sales people and businesspersons when electricity is not available. The success of the photovoltaic power supply is largely determined by lighting conditions: outdoors, a device is exposed to solar intensities of up to 1000w/m but indoors, under artificial desktop lighting or outdoors during overcast weather, the value decreases to 100w/m. The cells should provide close to maximum voltage already for very low illumination and for a very small area of cells for cellular phones, laptops and PDAs. These specifications are well met by highefficiency cells exceeding 14-15% efficiency in our devices. We have developed a solar charging device for commercially available PDAs, mobile phones and laptops. The charging device consists of a 9-30 solar cell generator connected in string using black on black technology with an area of 5×12 cm and 1.5 watt related power with a low loss charge controller for the Li-Ion battery in the PDAs and mobile phones, and a 33×33 cm 10w power device for the laptops. The present invention is related to solar power devices, which are capable of performing the conversion of solar energy to electrical energy (photovoltaic principle), and in particular which are useful for providing power to handheld devices, whether indoors (inside of a building or other enclosure) or outdoors (outside of a building or other enclosure).

Abstract: Solar cell (SC) cost reduction remains the main problem in PV development. Selfformation technology implementation is one of the ways to decrease this cost. It is known planar object.s evolution approximation by 8-dimensional topological space, containing object geometry, set of parameters, medium set and matrix of interaction. There we can have some different cases: external formation, self-formation, development and reproduction. However in case of self-formation, these attributes are not sufficient, because the different sequences of media can be created from the same set of medium. In external formation all structured and chaotic media are brought from outside and technological graph is created from recurrent parts. There we see an object interaction with different structured media, which structures are transferred to evolving object, and recurrent sequence of chaotic media (deposition, exposure, development, etching, diffusion and oxidizing). Initial technological object, interaction matrix and set of interactions are not sufficient to unambiguous technological process describing in self-formation case as well. Some technological graphs may be valid to one interaction matrix and result different final object. Medium there are changed from outside but the initial object changes as the result of interaction with medium. In optimal case one structured medium (for initial object formation) and the sequence of chaotic media are necessary to manufacture the solar cell from the silicon wafer. The approach of technological graph to solar cell technology is presented. Graphs of external formation and self-formation of solar cell are compared.

Abstract: Periodic precipitation pattern formation in reaction diffusion systems is interpreted as a moving boundary problem. All the existing laws are reexamined on the basis of the moving boundary assumption. Experimental observations were found to be in good agreement with the new equations suggested.