Electrical transport properties in Co‐silicides formed by thin‐film reactions

Four different Co‐silicide compounds were obtained by solid‐state reaction at 800 °C in thin bilayers of amorphous silicon and cobalt evaporated on SiO2 substrates. Rutherford backscattering spectroscopy (2 MeV 4He+), x‐ray diffraction, and Auger electron spectroscopy were used to obtain information about the chemical and crystallographic characteristics of the samples. Results indicate that in each sample only one of the following phases is present: CoSi2, CoSi, Co2Si, and Co4Si, the latter identified on the basis of the stoichiometric ratio only. Electrical resistivity and Hall effect measurements on van der Pauw structures were carried out as a function of the temperature in the intervals: 10–1000 and 10–300 K, respectively. At room temperature the resistivity ranges from the value 19 μΩ cm for CoSi2 to the value 142 μΩ cm for CoSi. There are some analogies with the case of a classical metal, but remarkable differences are also detectable in the resistivity versus temperature behavior and in the order ...