Intermixing at the heterointerface between ZnS Zn S,O bilayer buffer and CuInS2 thin film solar cell absorber

The application of Zn compounds as buffer layers was recently extended to wide gap CuInS2 CIS based thin film solar cells. Using a new chemical deposition route for the buffer preparation aiming at the deposition of a single layer, nominal ZnS buffer without the need for any toxic reactants such as, e.g. hydrazine has helped to achieve a similar efficiency as respective CdS buffered reference devices. After identifying the deposited Zn compound, as ZnS Zn S,O bi layer buffer in former investigations [M. Bär, A. Ennaoui, J. Klaer, T. Kropp, R. S ez Araoz, N. Allsop, I. Lauermann, H. W. Schock, and M.C. Lux Steiner, Formation of a ZnS Zn S,O bilayer buffer on CuInS2 thin film solar cell absorbers by chemical bath deposition , J. Appl. Phys., accepted.], this time the focus lies on potential diffusion intermixing processes at the buffer absorber interface possibly, clarifying the effect of the heat treatment, which drastically enhances the device performance of respective final solar cells. The interface formation was investigated by x ray photoelectron and x ray excited Auger electron spectroscopy. In addition, photoelectron spectroscopy PES measurements were also conducted using tuneable monochromatized synchrotron radiation in order to gain depth resolved information. The buffer side of the buffer absorber heterointerface were investigated by means of the characterization of Zn S,O ZnS CIS structures where the ZnS Zn S,O bi layer buffer was deposited successively by different deposition times. In order to make the in terms of PES information depth deeply buried absorber side of the buffer absorber heterointerface accessible for characterization, in these cases the buffer layer was etched away by dilute HClaq. We found that while out leached Cu from the absorber layer forms together with the educts in the chemical bath a Zn 1 Z ,Cu2Z S like interlayer between buffer and absorber, Zn is incorporated in the uppermost region of the absorber. Both effects are strongly enhanced by postannealing the Zn S,O ZnS CIS samples. However, it was determined that the major fraction of the Cu and Zn can be found quite close to the heterointerface in the buffer and absorber layer, respectively. Due to this limited in the range of one monolayer spatial extent, these diffusion mechanisms were rather interpreted as a CBD induced and heat treatment promoted Cu Zn ion exchange at the buffer absorber interface. Possible impacts of this intermixing on the performance of the final solar cell devices will also be discusse

The Digital Fish Library: Using MRI to Digitize, Database, and Document the Morphological Diversity of Fish

Museum fish collections possess a wealth of anatomical and morphological data that are essential for documenting and understanding biodiversity. Obtaining access to specimens for research, however, is not always practical and frequently conflicts with the need to maintain the physical integrity of specimens and the collection as a whole. Non-invasive three-dimensional (3D) digital imaging therefore serves a critical role in facilitating the digitization of these specimens for anatomical and morphological analysis as well as facilitating an efficient method for online storage and sharing of this imaging data. Here we describe the development of the Digital Fish Library (DFL, http://www.digitalfishlibrary.org), an online digital archive of high-resolution, high-contrast, magnetic resonance imaging (MRI) scans of the soft tissue anatomy of an array of fishes preserved in the Marine Vertebrate Collection of Scripps Institution of Oceanography. We have imaged and uploaded MRI data for over 300 marine and freshwater species, developed a data archival and retrieval system with a web-based image analysis and visualization tool, and integrated these into the public DFL website to disseminate data and associated metadata freely over the web. We show that MRI is a rapid and powerful method for accurately depicting the in-situ soft-tissue anatomy of preserved fishes in sufficient detail for large-scale comparative digital morphology. However these 3D volumetric data require a sophisticated computational and archival infrastructure in order to be broadly accessible to researchers and educators

Linking phenotypic correlations from a diverse set of laboratory tests to field behaviors in the crayfish, Orconectes virilis

The presence of phenotypic behavioral correlations and their connection to fitness consequences of organisms have received considerable debate within the literature. Yet, little work has been carried out to connect any behavioral correlates found within a set of laboratory studies to natural behavior observed under complex environmental conditions. To help fill this gap, individual crayfish, collected from the same local population, completed five different behavioral assays in a laboratory setting in a random order. These data were used to reveal any possible correlations for behavioral scores across all of the laboratory tests. Subsequently, these same individuals were placed into the field and video recorded for 24 hr. A separate set of field behaviors, related to the laboratory assays, were quantified from the field videos. The normalized laboratory and field behaviors were used in three stepwise statistical analyses. First, normalized data were loaded into a PCA to generate a priori hypotheses on potential behavioral correlates. These hypotheses were subsequently tested using general multiple linear regression. Finally, structural equation modeling was performed to elucidate any behavioral modules from the laboratory assays that correlated with behavioral patterns present from the fieldwork. Three laboratory‐based behavioral modules were connected to three separate field assays: exploration–avoidance, bold–shy, and aggressiveness. Yet, some behaviors exhibited in the laboratory assays were uncorrelated with any behaviors found in the field and vice versa. Results from this study provide evidence that although many different behavioral correlates may exist within laboratory settings, these same modules may not translate directly into predicting behavior under natural settings.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/143757/1/eth12734_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/143757/2/eth12734.pd

Erzeugung dreidimensionaler Mikrostrukturen. Teilvorhaben: Herstellung und Charakterisierung metallischer Mikrospulen und induktiver Sensoren Abschlussbericht

SIGLEAvailable from TIB Hannover: DtF QN1(85,23) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman

Thermo-mechanical behavior and reliability issues for high temperature interconnections

Transient liquid phase (TLP) soldering is one option for high temperature interconnects with the advantage of processing conditions being close to those for conventional soldering. In the Cu-Sn system addressed in the paper, a high post-processed melting point of the solder interconnects is achieved due to the formation of Cu6Sn5 and Cu3Sn intermetallic compounds (IMC). A specific low melting solder paste under development can be used if applications for both power and logic electronics are addressed. Metallic particles are embedded in the solder paste. New challenges concerning the thermo-mechanical reliability of these devices arise as the materials properties of the TLP interconnect differ substantially from those known for soft solders. Based on material characterization of pure IMC effective material characteristics of the TLP joint, consisting of a mixture of different constituents, have been derived based on a micromechanical cell model. A cell model was additionally embedded in a resistor joint with effective TLP properties and the local stresses were studied. It is shown that the higher material stiffness and strongly decreasing ductility of the joining material change the potential failure modes of an assembly made by TLP soldering. The new thermo-mechanical failure risks are evaluated for a mounted chip resistor and a power module, an IGBT on DCB substrate, by both conventional FEA and cohesive zone modeling

Phase segregation, Cu migration and junction formation in Cu(In, Ga)Se

A reinvestigation of the phase diagram of the Cu–In–Se system along the quasi-binary cut In2Se3–Cu2Se reveals an existence range of the chalcopyrite α-phase that is much narrower than commonly accepted. The presence of 0.1% of Na or replacement of In by Ga at the at.% level widens the existence range of the α-phase, towards In- and Ga-rich compositions. We also investigate the interplay between phase segregation and junction formation in polycrystalline Cu(In, Ga)Se2 films. Here, we attribute the band bending observed at bare surfaces of the films to a positively charged surface acting as a driving force for the formation of a Cu-poor surface defect layer via Cu-electromigration. The electrical properties of this defect layer are different from those found for the bulk β-phase. We suggest that Cu-depletion is self-limited at the observed In/(In+Cu) surface composition of 0.75 because further Cu-depletion would require a structural transformation. Capacitance measurements reveal two types of junction metastabilities: one resulting from local defect relaxation, invoked to explain a light-induced increase of the open-circuit voltage of Cu(In, Ga)Se2 solar cells, and one due to Cu-electromigration