In situ analysis of elemental depth distributions in thin films by combined evaluation of synchrotron x ray fluorescence and diffraction

Abstract In this work we present a method for in situ analysis of elemental depth distributions in thin films by a combined evaluation of synchrotron x ray fluorescence XRF and energy dispersive x ray diffraction EDXRD signals. We recorded diffraction and fluorescence signals simultaneously during reactive annealing of thin films. By means of the observed diffraction signals the time evolution of phases in the thin films during the annealing processes can be determined. We utilized this phase information to parameterize depth distributions of the elements in the films. The time dependent fluorescence signals were then taken to determine the parameters representing the parameterized depth distributions. For this latter step, we numerically calculated fluorescence intensities for a given set of depth distributions. These calculations handle polychromatic excitation and arbitrary functions of depth distributions and take into account primary and secondary fluorescence. The influence of lateral non uniformity of the films as well as accuracy limits of the method are investigated. We apply the introduced method to analyze the evolution of elemental depths distributions and to quantify kinetic parameters during a synthesis process of CuInS2 thin films by reactive annealing of Cu In precursors in sulfur atmospher

An Integrated Chemical Cytometry Method: Shining a Light on Akt Activity in Single Cells

Tools to evaluate oncogenic kinase activity in small clinical samples have the power to guide precision medicine in oncology. Existing platforms have demonstrated impressive insights into the activity of protein kinases, but these technologies are unsuitable for the study of kinase behavior in large numbers of primary human cells. To address these limitations, we developed an integrated analysis system which utilizes a light-programmable, cell-permeable reporter deliverable en masse to many cells. The reporter's ability to act as a substrate for Akt, a key oncogenic kinase, was masked by a 2-4,5-dimethoxy 2-nitrobenzyl (DMNB) moiety. Upon exposure to ultraviolet light and release of the masking moiety, the substrate sequence enabled programmable reaction times within the cell cytoplasm. When coupled to automated single-cell capillary electrophoresis, statistically significant numbers of primary human cells were readily evaluated for Akt activity

Time resolved investigation of Cu In,Ga Se2 growth and Ga gradient formation during fast selenization of metallic precursors

Ga segregation at the backside of Cu In,Ga Se2 solar cell absorbers is a commonly observed phenomenon for a large variety of sequential fabrication processes. Here, we investigate the correlation between Se incorporation, phase formation and Ga segregation during fast selenisation of Cu In Ga precursor films in elemental selenium vapour. Se incorporation and phase formation are analysed by real time synchrotron based X ray diffraction and fluorescence analysis. Correlations between phase formation and depth distributions are gained by interrupting the process at several points and by subsequent ex situ cross sectional electron microscopy and Raman spectroscopy. The presented results reveal that the main share of Se incorporation takes place within a few seconds during formation of In Se at the top part of the film, accompanied by outdiffusion of In out of a ternary Cu In Ga phase. Surprisingly, CuInSe2 starts to form at the surface on top of the In Se layer, leading to an intermediate double graded Cu depth distribution. The remaining Ga rich metal phase at the back is finally selenised by indiffusion of Se. On the basis of a proposed growth model, we discuss possible strategies and limitations for the avoidance of Ga segregation during fast selenisation of metallic precursors. Solar cells made from samples selenised with a total annealing time of 6.5 amp; 8201;min reached conversion efficiencies of up to 14.2 total area, without anti reflective coating . The evolution of the Cu In,Ga Se2 diffraction signals reveals that the minimum process time for high quality Cu In,Ga Se2 absorbers is limited by cation ordering rather than Se incorporatio

CdS/Cu(In,Ga)S2 based solar cells with efficiencies reaching 12.9% prepared by a rapid thermal process

In this letter, we report externally confirmed total area efficiencies reaching up to 12.9% for CdS/Cu(In,Ga)S2 based solar cells. These are the highest externally confirmed efficiencies for such cells. The absorbers were prepared from sputtered metals subsequently sulfurized using rapid thermal processing in sulfur vapor. Structural, compositional, and electrical properties of one of these champion cells are presented. The correlation between the Ga distribution profile and solar cell properties is discussed

The role of interparticle heterogeneities in the selenization pathway of Cu Zn Sn S nanoparticle thin films a real time study

Real time energy dispersive X ray diffraction EDXRD analysis has been utilized to observe the selenization of Cu Zn Sn S nanoparticle films coated from three nanoparticle populations Cu and Sn rich particles roughly 5 nm in size, Zn rich nanoparticles ranging from 10 to 20 nm in diameter, and a mixture of both types of nanoparticles roughly 1 1 by mass , which corresponds to a synthesis recipe yielding CZTSSe solar cells with reported total area efficiencies as high as 7.9 . The EDXRD studies presented herein show that the formation of copper selenide intermediates during the selenization of mixed particle films can be primarily attributed to the small, Cu and Sn rich particles. Moreover, the formation of these copper selenide phases represents the first stage of the CZTSSe grain growth mechanism. The large, Zn rich particles subsequently contribute their composition to form micrometer sized CZTSSe grains. These findings enable further development of a previously proposed selenization pathway to account for the roles of interparticle heterogeneities, which in turn provides a valuable guide for future optimization of processes to synthesize high quality CZTSSe absorber layer