Current-voltage characteristics and layer coupling in amorphous W/Si multilayers

Current-voltage (I-V) characteristics have been measured on the amorphous W monolayers and W/Si multilayers in the absence of magnetic field. For the monolayers and the multilayers with thick Si layers, the I-V curves show straight lines on a log-log scale and the Kosterlitz-Thouless transition. On the other hand, for the multilayers with thin Si layers, they show negative curvatures on such a scale at low temperatures. This is attributed to the effect of interlayer coupling giving rise to the dimensional crossover of vortex configuration. Our results are discussed with the theories which take the coupling effect into consideration.