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  • 1
    Keywords: Forschungsbericht ; Akkumulator
    Type of Medium: Online Resource
    Pages: Online-Ressource (PDF-Datei: 34 S., 2.253 KB) , Ill., graph. Darst.
    Language: German
    Note: Unterschiede zwischen dem gedruckten Dokument und der elektronischen Ressource können nicht ausgeschlossen werden , Förderkennzeichen BMBF 03X4618B. - Verbund-Nr. 01088625 , Systemvoraussetzungen: Acrobat reader.
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  • 2
    ISSN: 1432-0630
    Keywords: PACS: 64.60.Ak; 68.45.-v; 82.40.-g; 82.45.+z; 82.65.-i
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The physical character of local oscillators on a nm scale will be outlined. Next-neighbor coupling leads to percolation areas of about 100 nm as result of Monte Carlo simulations. The percolation provides an intrinsic synchronization mechanism leading to macroscopic oscillations.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 8 (1975), S. 319-331 
    ISSN: 1432-0630
    Keywords: Self-interstitials in silicon ; Swirls ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Point defect agglomerates in dislocation-free silicon crystals, usually called “swirls”, have been investigated by means of high-voltage electron microscopy. It was found that a single swirl defect consists of a dislocation loop or a cluster of dislocation loops. By contrast experiments it could be shown that these loops are formed by agglomeration of self-interstitial atoms. Generally the loops have a/2〈110〉 Burgers vectors, but in specimens with high concentrations of carbon (∼1017 cm−3) and oxygen (∼1016 cm−3) also dislocation loops including a stacking fault were observed. In crystals grown at growth rates higher thanv=4 mm/min no swirls are observed; lower growth rates do not markedly affect the size and shape of the dislocation loops. With decreasing impurity content (particulary of oxygen and carbon) the swirl density decreases, whereas the dislocation loop clusters become larger and more complex. A model is presented which describes the formation of swirls in terms of agglomeration of silicon self-interstitials and impurity atoms.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 63 (1996), S. 153-159 
    ISSN: 1432-0630
    Keywords: 68.00 ; 82.45 ; 85.30
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The development of a micromachining technique for processing arbitrary structures with high aspect ratios in bulk silicon is presented. It is based on utilizing standard microelectronic processes and electrochemical macropore formation onn-type silicon in electrolytes containing hydrofluoric acid. This pore-etching technique allows us to produce very regular pore arrays with pore diameters and distances in the micrometer range and pore lengths up to wafer thickness. Samples with prefabricated pore arrays which differ in pore spacing, pore diameter and geometry are used as substrates for a micromachining process. The pores will facilitate the anisotropic etch profile which is required for the desired high aspect ratios although an isotropic etch process is used. Very deep microstructures with steep pore walls and aspect ratios of 10–15 are produced with this technique. It is shown that smaller pore array dimensions improve microstructure resolution.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 53 (1991), S. 8-19 
    ISSN: 1432-0630
    Keywords: 82.45 ; 61.70 ; 68.45
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A number of interesting and still not fully understood phenomena occur if silicon is used as an electrode in an electrochemical cell. Effects include porous silicon layer (PSL) formation with features on a nanometer scale, surface roughening on a micrometer scale, quantum efficiencies for light generated currents much larger than 1, preferential etching of defects, electropolishing, and voltage or current oscillations. It is shown that despite the complexities of chemical reactions involved, a basic understanding of the electrode behavior is possible from a semiconductor physics point of view and that it can be advantageous to use the silicon — electrolyte junction for analytical purposes. Topics such as defect characterization, measurements of minority carrier diffusion length, or surface recombination velocities can be addressed in unique ways by taking advantage of particular properties of the silicon — hydrofluoric acid system. Based on the general description of the Si — electrolyte junction given in this paper, strengths and limitations of some electrochemical methods are discussed in some detail and illustrated by examples.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 52 (1991), S. 52-59 
    ISSN: 1432-0630
    Keywords: 81.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Rapid thermal processing (RTP) of silicon wafers is a promising technique for submicron device structures. Heating is achieved by an intense light-source which allows one to obtain very high temperatures in very short times. Problems arise from temperature gradients. Both experiments and theoretical calculations show that a nonuniform lamp intensity improves the temperature uniformity only in a stationary state when only nonuniform back-reflection of heat radiation by the reflector has to be compensated. This measure, however, causes a dramatic transitory nonuniformity which hampers future applications of RTP especially with larger wafer sizes. The deteriorating influence is demonstrated with shallow junction formation, plastic deformation of the wafer (slip), and aluminum alloying as examples.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 50 (1990), S. 141-150 
    ISSN: 1432-0630
    Keywords: 81.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A theory of wafer heating during rapid thermal processing is presented. It is demonstrated that temperature uniformity is not only limited by radiation loss at the wafer edge in the stationary state but also influenced by transient effects during temperature ramping. Whereas a compensation of edge losses call for enhanced illumination intensities at the wafer periphery, the avoidance of transient temperature gradients would require uniform illumination. Calculations for various system configurations lead to optimized processing cycles and suggest possible improvements of RTP equipment.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Journal of porous materials 7 (2000), S. 201-204 
    ISSN: 1573-4854
    Keywords: macroporous silicon ; photonic crystal ; microstructuring ; waveguides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Uniformity and high refractive index contrast make macroporous silicon an ideal two-dimensional photonic crystal, that can be tailored over a wide range of frequencies. For optical transmission measurements the porous silicon has to be structured further. Light has to be coupled in perpendicular to the pore axis and to traverse a well defined number of pore layers. For this purpose a lateral structuring technique has been developed that allows to remove the porous silicon with a precision of less than one pore lattice constant. Bars of macroporous silicon which are 100 μm high, 2–200 μm wide and several mm long have been prepared. These bars have been aligned with designed defect structures like linear or bent waveguides in the porous silicon. The achieved samples are well suited to investigate the optical properties of these defects with light traveling perpendicular to the pore axis.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1573-4854
    Keywords: macropore formation ; crystal orientation dependence ; 〈113〉 orientation ; anodic potential dependence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The formation of macropores on anodically biased n-type silicon with backside-illumination was investigated as a function of crystal orientation and bias voltage. Specimens were cut from bulk crystals with various orientations from {100} to {111}, polished and subjected to anodic etching in HF. The resulting pores were investigated on cleaved samples by SEM. All pores were found to grow in either a 〈100〉 direction or a 〈113〉 direction, depending on the misorientation angle. This finding applies also to the branching of a single pore. The results can be understood if the valence for the dissolution reaction is approximately 2.6 in 〈100〉 and approximately 4 in the 〈113〉 direction, and if all other directions are not allowed for the growth of pores in Si.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1573-4854
    Keywords: macropore formation ; illumination ; temperature dependence ; anodic potential ; doping dependence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Applying an anodic bias on a silicon HF contact and illuminating the backside of a n-type silicon wafer allows to create macropores. The formation of “random macropores” is studied in this paper by determination of the influences of the potential, the temperature and the doping level. A statistical approach is used to evaluate the micrographs. The formation of the macroporous layer consists of two phases. Beginning with a plane surface and homogeneous dissolution of silicon, first pores occur after some time. In this nucleation phase the thickness of the homogeneously dissolved Si depends strongly on the doping level and the temperature but only weakly on the applied bias. In a second phase of stable pore growth the density of pores is investigated as a function of temperature and anodic potential. For low doped material we find a strong stabilisation influence of the deep space charge region (SCR) in the nucleation as well as in the stable pore growth phase. Thus an increased anodic bias decreases the density of pores. For highly doped silicon no stabilisation influence of the SCR is found. The pore growth is dominated by the electrochemical dissolution rate, i.e. increasing the potential increases the density of the macropores.
    Type of Medium: Electronic Resource
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