Relation of nanoscale and macroscopic properties of mixed-phase silicon thin films

Scanning probe methods (SPMs) such as conductive atomic force microscopy (C-AFM) can be used to probe the structure and local conductivity of the mixed phase silicon thin films with nanometer resolution. Effective medium approximations (EMAs) were used to relate the nanoscale properties with effective macroscopic properties for the dark conductivity measured with coplanar contacts. Comparison of the percolation threshold predicted by diffferent EMAs show partial correlation of the structure, with resistive amorphous phase coating the conductive grains. In sandwich structures (such as solar cells) the local fields may play important role: concentration of both optical and electrical internal fields to the tips of spherically capped conical microcrystalline grains. Adaptive higher-order polynomial finite-element methods (FEMs) were used to calculate the internal field distributions in the C-AFM. The calculated values agree with the experimental C-AFM, providing the first quantitative description of the relation of the nanoscale and macroscopic properties of the mixed phase Si films. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim