Resistivity, Hall-effect, and magnetoresistance measurements have been performed in the temperature range 4.2-300 K on thin fihns of the er-Cu3Ge phase that has a long-range ordered monoclinic crystal structure. The results show that et-Cu3Ge is a metal with a room-temperature resistivity of -6 @ cm. The temperature dependence of resistivity follows the Block-Griineisen model with a Debye temperature of 240*25 K. The density of charge carriers, which are predominantly holes, is -8 X 10z2/cm3 and is independent of temperature and 8lm thickness. The Hall mobility at 4.2 K is -132 cm2/V s. The elastic mean free path is found to be -1200 A, which is surprisingly large for a metallic compound film. The results show that the residual resistivity is dominated by surface scattering rather than grain-boundary scattering. An increase in Ge concentration above 25 at. % (but less than 35 at. %) is found to affect the resistivity and Hall mobility, but not the density of charge carriers.
Articles you may be interested inElectronic transport properties on transition-metal terminated zigzag graphene nanoribbons Electrical resistivity in the temperature range of 2-1100 K and Hall-effect measurements from 10 to 300 K of CoSi 2 , MoSi 2 , TaSi 2 , TiSi 2 , and WSi 2 polycrystalline thin films were studied. Structure, composition, and impurities in these films were investigated by a combination of techniques of Rutherford backscattering spectroscopy, x-ray diffraction, transmission electron microscopy, and Auger electron spectroscopy. These silicides are metallic, yet there is a remarkable difference in their residual resistivity values and in their temperature dependence of the intrinsic resistivities. For CoSi 2 , MoSi 2 , and TiSi 2 , the phonon contribution to the resistivity was found to be linear in temperature above 300 K. At high temperatures, while a negative deviation from the linearity followed by a quasisaturation was observed for TaSi 2 , the resistivity data ofWSi 2 showed a positive deviation from linearity. It is unique that the residual resistivity, p(2 K), of the WSi 2 films is quite high, yet the temperature dependent part, i.e., p(293 K) -p(2 K), is the smallest among the five silicides investigated. This suggests that the room-temperature resistivity of WSi 2 can be greatly reduced by improving the quality of the film, and we have achieved this by using rapid thermal annealing.
GdSi2 and ErSi2 polycrystalline thin films were studied using electrical resistivity in the temperature range 10–900 K, Hall effect from 10–300 K and reflectivity spectra from 0.2–100 μm at room temperature. Composition and structure in these films were investigated by Rutherford backscattering spectroscopy and x-ray diffraction techniques. These silicides are metallic with (i) a remarkable difference in their residual resistivity, (ii) a phonon contribution to the resistivity which showed a negative deviation linearity, and (iii) low energy interband transitions. Resistivity data indicated that GdSi2 and ErSi2 have a Debye temperature of 328 and 300 K respectively and a limiting resistivity value much higher than that observed in other transition metal disilicides. The charge carrier concentration was estimated to be 4×1021 cm−3 at room temperature according to Hall measurements, and the mean free path was 63 Å and 320 Å for GdSi2 and ErSi2, respectively, at 10 K. The parameters obtained by the optical analysis are in good agreement with those extracted from the transport measurements, thus permitting one to obtain a reasonable value for the Fermi velocity.
The electrical resistivity of monocrystalline TiSi2, TaSi2, MoSi2, and WSi2 has been measured from 4.2 to 1100 K. These disilicides are metallic, yet there is a remarkable difference in the temperature dependence of their intrinsic resistivities. TiSi2 and TaSi2 are found to exhibit a T5 dependence in the temperature range of 13<T<30 K and 15<T<28 K, respectively, while MoSi2 and WSi2 show a T3.8 dependence from 15 to 40 K. For TiSi2, along the three crystallographic directions 〈100〉, 〈010〉, and 〈001〉, the phonon contribution to the resistivity was found to be linear in temperature above 300 K. The same behavior was observed for TaSi2 along the 〈0001〉 axis, while a negative deviation from the linearity followed by a quasisaturation was observed with the current, parallel to the 〈101̄0〉 axis. The resistivity data of WSi2 and MoSi2 with the current parallel to 〈001〉 and 〈110〉 crystallographic directions showed a positive deviation from linearity. The data are fitted to several theoretical expressions at low temperatures and in the full range of temperatures. The results are discussed in light of these theories.
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 of magnitude of the resistivity and of the Hall coefficient. In particular, at T>300 K the resistivity of the CoSi2 samples linearly depends on temperature and is well fitted by the classical Bloch–Grüneisen expression. The other silicides show, in the same temperature range, a deviation from linearity (d2ρ/dT2<0), while a quasi saturation of the resistivity can be extrapolated at higher temperatures. This saturation phenomenon can be described by the parallel of an ideal conductivity and of a saturation conductivity, and associated with the electron mean free path approaching interatomic distances. A similar model already has been put forth to describe the saturation of the resistivity in systems, such as A-15 superconducting compounds, characterized by a high value of the room-temperature resistivity. The transport parameters, deduced in a free electron framework from the resistivity curves of the Co silicides, show values which are consistent with the proposed model. Hall coefficient versus temperature behavior indicates that between 10 and 300 K a multicarrier effect is present. Conduction is predominantly n type in CoSi and p type in the other silicides.
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