The temperature and volume fraction dependence of the resistivity of granular Al-Ge near the percolation threshold

摘要: Extensive measurements of the temperature and Al volume fraction dependence resistivity granular Al-Ge have been made near percolation threshold phi c. The results at 295 K are analysed using equations, as modified by Efros Shklovskii, Straley, for systems where two components finite conductivity ratios, fitting to general effective media (GEM) equation, which also takes into account conductivities both components. parameters these equations (resistivities) components, critical exponents s t, (percolation) experimental value c, obtained from magnetoresistivity below superconducting transition Al, agrees remarkably well with values GEM equations. observed found be high, width region surprisingly large. Attempts extend this type analysis lower temperatures proved unsuccessful, it is concluded that more insulating component, namely amorphous Al-doped Ge, depends on total content sample. It shown c cannot identified versus curves between 5 K, nor derivatives curves. Graphs Ge individual samples extracted equation.