| The fact that classical percolation theory has some limitations to explain the giant Hall effect and other phenomena of granular films, promoted the development of quantum percolation theory. Based on quantum interference effects model, Wan and Sheng proposed a quantum-percolation theory, which have explained some abnormal phenomena in the percolation systems near the quantum-percolation threshold. X. X. Zhang's group observed the giant Hall effect from Cu-SiO2 granular films, which was consistent with the quantum-percolation model. However, expect for Zhang's observation, there is no other report about the giant Hall effect of nonmagnetic percolation systems. Therefore, we have prepared the Mo-SnO2 and Al-AlN nonmagnetic granular films by Rf magnetron sputtering method, and its microstructure and electrical transport properties are investigated systematically. The giant Hall effect is observed in Mo-SnO2 composites, and the influence of microstructure on the electrical transport properties has been discussed. The microstructure analysis of our films shows good nanopaticle structure, that a mass of nanometer level metal particles are distributed among the amorphous state matrix.With decreasing metal volume fraction, the two systems reveal more obvious nonmetallic characteristics in transport properties gradually, and metal-insulator transition is found in the Al-AlN system. For Mo-SnO2 system, the dependence between resisitivity and Mo volume fraction at lower temperature is much stronger than that at higher temperature. We have analyzed the resistivity data using three dimensional classical percolation theory, and the classical-percolation threshold has been determined as 0.32, which is quite comparable to the theoretical value of 0.3117±0.0003 in three dimensional bond percolation models. For Al-AlN system, a lnT dependence of the conductivity is found within a certain range of temperature, which is consistent with the theory of K. B. Efetpov.The Hall coefficient of two systems increases with decreasing metal volume fraction. For Mo-SnO2 system, it reaches maximum 1.55×10-8 m 3/ C when metal volume fraction reduces to 0.359, the ratio of the highest value of Hall coefficient to the lowest is about 800, enhances almost 3 orders of magnitude. Both of the two systems reveal positive magnetoresistance. The magnetoresistance increases with increasing nitrogen partial pressure for Al-AlN system, and it increases with increasing metal volume fraction for Mo-SnO2 system. Base on three dimensional weak localization theory, in which the spin-orbit scattering and the Maki-Thompson superconducting fluctuation effect are also included, we can analyze the magnetoresistance data and extract the dephasing length Lφ. When metal volume fraction is near the quantum-percolation threshold (x=0.359), the size of the small substructures in the sample are range from 0.7 nm to 3 nm, which is obviously smaller than the electron dephasing length extracted from fitting process. In this case, the local quantum interference effect among the particles plays important role in the electrical transport properties of the composites, leading to the occurrence of quantum Hall effect, therefore, our experimental results provide strong supports for the validity of quantum percolation theory of P. Sheng.
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