The metal-insulator transition in composite Al-Ge films has been extensively studied experimentally. Using the superconducting properties of percolating clusters composed of small aluminum grains in the presence of a magnetic field, the critical metallic volume fraction φc(sc) for the metal-insulator transition has been uniquely determined. The low temperature electrical conductivity data are examined using a number of criteria for φc. Some of these criteria are quite successful, yielding φc's to within one percent of φc(sc), the definitive value. However, one widely used criterion involving the fitting of the low temperature conductivity data to a T 1 2 dependence, which results from the electron-electron interaction theory, was found to yield a very different value of φc. Other methods and/or criteria, using room temperature conductivity data to determine φc, are evaluated. These also yield φc values that are within 1% of φc(sc).
|Number of pages||7|
|Journal||Physica A: Statistical Mechanics and its Applications|
|State||Published - 1 Jun 1994|