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  • 1
    Language: English
    In: Journal of Crystal Growth, 15 July 2012, Vol.351(1), pp.131-140
    Description: This work presents the results of a systematic study of mono- and poly-crystalline grain growth in directional solidification of silicon using different kinds of seed crystals. The seed orientation was varied between 〈100〉, 〈111〉 and 〈110〉. In some experiments the seeds were split into several seed pieces. The results show that the growth of misoriented grains at the crystal periphery as well as in the gaps between split seeds depends strongly on the crystallographic orientation of the seeds. It is shown that this problem can be minimized if certain seed orientations and combinations are chosen. Generally the 〈100〉 seed orientation turns out to be most difficult with respect to mono-crystalline growth. Heterogeneous nucleation originating from the crucible walls seems to be a minor problem. ► Growth of different oriented mono-crystals by casting technique is possible. ► Detailed investigation of the mc-grain structure in the crystals periphery. ► Proposal of a growth model which includes a twinning process. ► Validation of the model by experimental data.
    Keywords: A1. Crystal Structure ; A1. Directional Solidification ; A1. Growth Models ; A2. Seed Crystals ; A2. Single Crystal Growth ; Engineering ; Chemistry
    ISSN: 0022-0248
    E-ISSN: 1873-5002
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  • 2
    Language: English
    In: Journal of Crystal Growth, 01 April 2017, Vol.463, pp.1-9
    Description: Dislocation clusters are the main crystal defects in multicrystalline silicon and are detrimental for solar cell efficiency. They were formed during the silicon ingot casting due to the relaxation of strain energy. The evolution of the dislocation clusters was studied by means of automated analysing tools of the standard wafer and cell production giving information about the cluster development as a function of the ingot height. Due to the observation of the whole wafer surface the point of view is of macroscopic nature. It was found that the dislocations tend to build clusters of high density which usually expand in diameter as a function of ingot height. According to their structure the dislocation clusters can be divided into light and dense clusters. The appearance of both types shows a clear dependence on the orientation of the grain growth direction. Additionally, a process of annihilation of dislocation clusters during the crystallization has been observed. To complement the macroscopic description, the dislocation clusters were also investigates by TEM. It is shown that the dislocations within the subgrain boundaries are closely arranged. Distances of 40–30 nm were found. These results lead to the conclusion that the dislocation density within the cluster structure is impossible to quantify by means of etch pit counting.
    Keywords: A1. Characterization ; A1. Directional Solidification ; A1. Line Defects ; A2. Growth From Melt ; B1. Elemental Solids ; Engineering ; Chemistry
    ISSN: 0022-0248
    E-ISSN: 1873-5002
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  • 3
    Language: English
    In: Acta Materialia, October 2013, Vol.61(18), pp.6903-6910
    Description: The formation of dislocation pile-ups and related small-angle subgrain boundaries in block-cast multicrystalline silicon for photovoltaic applications has been studied by means of white-beam X-ray topography (WB-XRT). For this purpose, samples sliced perpendicular and parallel to the growth direction have been investigated in reflection and transmission geometry, respectively. During the growth process of the silicon ingot, the dislocation density increases. WB-XRT measurements revealed the formation of small-angle subgrain boundaries. The subgrains have a slightly changed orientation related to a rotation of ∼0.07–0.80° around an axis parallel to the growth direction. This tilt results from the high number of dislocations forming dislocation pile-ups and walls. The spacings between dislocations in such subgrain boundaries were found to be between 297 and 28 nm. A qualitative model for the formation of dislocation pile-ups is proposed.
    Keywords: Dislocations ; Grain Boundaries ; Synchrotron Radiation ; X-Ray Topography ; Multicrystalline Silicon ; Engineering
    ISSN: 1359-6454
    E-ISSN: 1873-2453
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  • 4
    Language: English
    In: Acta Materialia, July 2015, Vol.93, pp.129-137
    Description: Dislocations and dislocation networks in multi-crystalline (mc) silicon wafers for photovoltaic applications act as minority carrier recombination centers and thus limit the efficiency of solar cells. The literature shows results for a massive dislocation reduction by applying an annealing procedure in combination with and without an impurity gettering step. In this work different kinds of annealing experiments with mc silicon samples were carried out at 1200 °C and 1365 °C for 1 h to 96 h under an applied stress of up to 4.2 MPa under pure inert or boron containing atmospheres. The results show clearly that, under the used process conditions, a dislocation reduction could not be observed via defect selective etching using different kinds of etchants. It was found, that it is essential to carefully select the etching solution as the electrical resistivity of the samples might change after a respective thermal treatment, such that the eventually still present dislocations will not be overseen.
    Keywords: Multi-Crystalline Silicon ; Dislocation ; Characterization ; Photovoltaic ; Engineering
    ISSN: 1359-6454
    E-ISSN: 1873-2453
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  • 5
    Language: English
    In: Acta Materialia, 2015, Vol.93, p.129(9)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.actamat.2015.04.022 Byline: C. Reimann, J. Friedrich, E. Meissner, D. Oriwol, L. Sylla Abstract: Dislocations and dislocation networks in multi-crystalline (mc) silicon wafers for photovoltaic applications act as minority carrier recombination centers and thus limit the efficiency of solar cells. The literature shows results for a massive dislocation reduction by applying an annealing procedure in combination with and without an impurity gettering step. In this work different kinds of annealing experiments with mc silicon samples were carried out at 1200[degrees]C and 1365[degrees]C for 1h to 96h under an applied stress of up to 4.2MPa under pure inert or boron containing atmospheres. The results show clearly that, under the used process conditions, a dislocation reduction could not be observed via defect selective etching using different kinds of etchants. It was found, that it is essential to carefully select the etching solution as the electrical resistivity of the samples might change after a respective thermal treatment, such that the eventually still present dislocations will not be overseen. Article History: Received 27 February 2015; Revised 14 April 2015; Accepted 15 April 2015
    Keywords: Annealing ; Silicon
    ISSN: 1359-6454
    Source: Cengage Learning, Inc.
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  • 6
    In: Journal of Strength and Conditioning Research, 2017, Vol.31(7), pp.1994-1999
    Description: ABSTRACT: Altmann, S, Spielmann, M, Engel, FA, Neumann, R, Ringhof, S, Oriwol, D, and Haertel, S. Validity of single-beam timing lights at different heights. J Strength Cond Res 31(7): 1994–1999, 2017—The purpose of this study was to quantify the effect of different timing light heights on sprint time and the validity of measurement. Two single-beam timing gate systems were used to measure 30-m sprint time (splits at 5 and 10 m) in 15 healthy and physically active male subjects. System 1 was set up at a height of 0.64 m and system 2 at 0.25 m (initial timing light) and 1.00 m (each following timing light), respectively. Participants performed 3 valid trials. The recordings of a high-speed video camera were used as a reference. Sprint times of system 1 and system 2 differed significantly between each other and from the reference system at all distances (p 〈 0.001). Intraclass correlation coefficients and Pearsonʼs r values between both timing light systems and the reference system were low to moderate at 5 and 10 m and moderate to high at 30 m. Bland and Altman analysis revealed that the agreement intervals were considerably higher for the comparison between system 1 and the reference system than for system 2 and the reference system. A valid measurement of splits at 5 and 10 m via the systems used in this study is questionable, whereas 30-m times have an acceptable validity, especially when using system 2. This study confirms the influence of methodological approaches on sprint times. Coaches and researchers should consider that results gained by single-beam timing lights at different heights are not comparable.
    Keywords: Light ; Time ; Running -- Physiology;
    ISSN: 1064-8011
    E-ISSN: 15334287
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  • 7
    Language: English
    In: Footwear Science, 01 June 2011, Vol.3, pp.S125-S127
    Description: Footwear Science Variability analysis of laboratory running
    Keywords: Engineering
    ISSN: 1942-4280
    E-ISSN: 1942-4299
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  • 8
    Language: English
    In: Journal of Crystal Growth, 15 September 2016, Vol.450, pp.14-21
    Description: The Alexander–Haasen model is applied for the analysis of dislocation dynamics in quasi-mono crystalline silicon. Model constants are re-calibrated using stress–strain measurements on small silicon samples under uniaxial compression. It is observed that the activation energy may decrease at low temperatures and the hardening parameter generally increases due to the presence of grown-in dislocation clusters. The calibrated model is applied to an idealized cooling process which allows for a discussion of the basic physical mechanisms leading to residual stresses in quasi-mono ingots. Residual stresses can be reduced by minimizing thermal stresses during the elastic–plastic transition, which was observed approximately between 1100 °C and 750 °C in the present case.
    Keywords: A1. Computer Simulation ; A1. Line Defects ; A1. Stresses ; A2. Bridgman Technique ; B2. Semiconducting Silicon ; Engineering ; Chemistry
    ISSN: 0022-0248
    E-ISSN: 1873-5002
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  • 9
    Language: English
    In: Journal of Crystal Growth, 15 October 2016, Vol.452, pp.272-275
    Description: Single crystal production of silicon for solar cell substrates has relied on the Dash neck technique developed more than 50 years ago. The technique is simple and repeatable and enables truly dislocation free crystal growth. It does have drawbacks, however, including limits on throughput and some structural difficulties. It has long been assumed that dislocation-free growth is not possible by any other method. In the ‘quasi-mono’ crystal growth technique, one of the key elements is the use of large area single crystal seeds. By melting the seeds at near-equilibrium conditions, it is feasible to avoid the production of dislocations during melting. We will review the dislocation relevant details of the large area seeding process and present best case results for dislocation density, including measured minority carrier lifetimes in excess of 1 ms on p-type material. We will focus on dislocation density exclusive of seed boundaries, but we will also present a potential best-case limit for the technique.
    Keywords: A1. Directional Solidification ; B2. Semiconducting Silicon ; B3. Solar Cells ; A2. Seed Crystals ; Engineering ; Chemistry
    ISSN: 0022-0248
    E-ISSN: 1873-5002
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  • 10
    Language: English
    In: Footwear Science, 01 June 2011, Vol.3, pp.S148-S150
    Description: Footwear Science Gender and age related requirements of running shoes: a questionnaire on 4501 runners
    Keywords: Engineering
    ISSN: 1942-4280
    E-ISSN: 1942-4299
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