Electrical and magnetoconductivity of binary and Fe-dopeda−RexSi1−xthin films ne

Abstract

The low-temperature electrical transport behavior of amorphous Re x Si 1Ϫx and Re x Fe y Si 1ϪxϪy thin films has been investigated as a function of temperature and magnetic field on the metallic side of the metal-insulator transition ͑MIT͒. In the temperature range above 20 K both undoped and Fe-doped films show the same approximately linear behavior of conductivity up to 300 K. At temperatures below 20 K the conductivity of the Re x Si 1Ϫx system can be understood on the basis of the theory of quantum corrections to the conductivity: The temperature dependence of the conductivity and the negative magnetoconductivity are caused by electronelectron interactions. The conductivity of Fe-doped films shows a completely different behavior. The comparison of undoped and Fe-doped films at the same ͑0͒ demonstrates that the width of the density of states anomaly near the Fermi energy ⌬ differs by two orders of magnitude. The positive contribution to the magnetoconductivity increasing strongly with decreasing temperature can be explained within a model of bound magnetic polarons and is related to additional spin scattering.

Variable-range hopping conduction and metal–insulator transition in amorphous RexSi1−xthin films

“…In samples 8 and 9, the local activation energy is zero within the error (see figure 5), exhibiting activationless or metallic behavior. The latter is in agreement with the previous results, addressed to the metallic side of the MIT [9]. Concerning samples 6 and 7, the reduced values of m for these samples are in agreement with the closest position of both samples to the MIT from the insulating side, as have been observed earlier (see [22] and references therein).…”

“…Recently, amorphous binary and Fe-doped Re x Si 1−x thin films were prepared [8,9]. Amorphous metal-semiconductor alloys represent a group of disordered materials with a length scale of disorder differing from that in highly doped crystalline semiconductors.…”

“…The low-temperature electrical transport of amorphous Re x Si 1−x and Re x Fe y Si 1−x −y thin films has been investigated as a function of the temperature and magnetic field on the metallic side of the MIT [9]. In the temperature range above 20 K both undoped and Fe-doped films demonstrated approximately the same linear behavior of conductivity up to 300 K. However, at low temperatures the resistivity and MR of these thin films exhibited significantly different behavior, and the larger the differences the shorter the distance to the MIT.…”