We report the atomic scale observation of a thin film growth mode related to grain boundaries in multilayers of polycrystalline gold and amorphous silicon. Using differential scanning calorimetry, in situ x-ray diffraction, and high-resolution electron microscopy, we observe silicide nucleation to take place at grain boundaries in the polycrystalline gold films followed by lateral silicide growth parallel to gold ͞silicon interfaces. This growth mode is related to solid-state reactions at low temperatures where atomic transport is restricted to grain and interphase boundaries. It demonstrates the importance of thin film microstructure for phase selection during thin film reactions at low temperatures.[S0031-9007(97)05118-1] PACS numbers: 81.10. Aj, 61.72.Mm, 81.15.Tv Metal silicides are of still growing interest as low resistivity contact materials for silicon devices. As device dimensions shrink, the controlled and reliable fabrication of silicides increasingly requires the understanding of basic mechanisms of thin film reactions. Thin film diffusion couples represent nonequilibrium systems frequently exhibiting large driving forces (¿k B T , k B : Boltzmann's constant) for phase formation. The final state to which such systems develop is simply determined by the minimum of the Gibbs free energy of the alloy system. The number of intermediate phases accessible by the system increases with increasing driving force. Which of these phases is selected in the early stages of the reaction is determined by the kinetics of the system when it follows the path towards this phase. Frequently, relaxation occurs via metastable intermediate phases, a prominent example being the well-known solid-state amorphization reactions between early and late transition metals [1].For the high-temperature regime where bulk interdiffusion is possible, bulk thermodynamics and kinetics can be used to describe phase selection in terms of nucleation [2] and growth kinetics [2-5] of the competing phases. It is commonly assumed that the product phase nucleates homogeneously at the interface between the parent phases ("a͞b interface") [2] or heterogeneously at triple points with grain boundaries followed by coalescence of the nuclei along the a͞b interface [2,6,7]. In both cases, nucleation evolves into the frequently observed planar growth of the product phase.In the low-temperature regime of negligible bulk diffusion, atomic transport is restricted to defective regions like interfaces, dislocations, and grain boundaries [8][9][10][11]. As a consequence, certain intermediate phases may no longer be accessible from the initial state by thermal fluctuations implying bulk thermodynamics and kinetics to be of lim-ited use for the prediction of the reaction path towards equilibrium. Instead, it seems obvious that microscopic details of the available diffusion paths are of increasing importance. This has been recognized in a recently proposed model which uses irreversible thermodynamics to calculate the effective driving force for product phase nuc...

A stabilized total‐area efficiency above 10% (ISC = 1.46 A, VOC = 148 V, FF = 67%, Pmpp = 145W, total area of 1.43m2) has been achieved on Gen 5 modules for the first time with an amorphous/microcrystalline silicon solar cell. The efficiency was enhanced by improving the light management and reducing the light induced degradation. The short circuit current density Jsc was enhanced by the introduction of internal light trapping using textured ZnO as the front transparent conductor, the implementation of an innovative µc‐SiOx based p‐layer and by an optical filter between the top and bottom cells of the tandem junction. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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