Electrical conductivity and hall effect of laser quenched amorphous Pt xSi 1−x alloys near the metal insulator transition

Abstract

We have measured the electrical conductivity σ and the Hall-coefficient R H of amorphous laser quenched Pt xSi 1−x thin films in the concentration range x = 7–35%. All samples were on the metallic side of the metal insulator transition (MIT). Our data show that the MIT in PtSi is dominated by Coulomb interaction. At low temperatures σ shows a √T factor g̃s 1 we have calculated the Coulomb gap parameter Δ. This quantity depends on the resistivity ϱ like Δ ∼ ϱ -2 and is in agreement with data taken from measurements of the tunneling density of states of amorphous Nb xSi 1−x and of granular aluminum. The conductivity as a function of Pt concentration x behaves like σ = σ 0(x/x c-1) ν with a critical concentration x c of about 5 % and a critical exponent ν=1.05±0.1. This exponent is in agreement with the relevant theories. Our Hall effect measurements performed at 77K show a concentration dependence as R H∼1/(x/x c-1) ν RH . The critical concentration x c of R H is the same as for the conductivity σ. The critical exponent ν RH was found to be 1.06±0.1.