Thin (<1000 A) hydrogenated nanocrystalline silicon films are widely used in solar cells, light emitting diodes, and spatial light modulators. In this work the conductivity of doped and undoped amorphous-nanocrystalline silicon thin films is studied as a function of film thickness: a giant anisotropy of conductivity is established. The longitudinal conductivity decreases dramatically (by a factor of 10~9-10~(10)) as the layer thickness is reduced from 1500 A to 200 A, while the transverse conductivity remains close to that of a doped a Si:H. The data obtained are interpreted in terms of the percolation theory.
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