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.
The Volta potential difference between Ih ice single crystals and different metals has been measured as a function of the temperature by using the vibrating electrode technique. Reproducible results have been obtained with ice–gold and ice–copper contacts, indicating that in these cases the equilibrium has been attained. At temperatures below −30 °C the dependence is linear, and we think that this is the effect of the impurity content on the ice Fermi level. At higher temperatures a term which is logarithmic in (Tm−T), where Tm is the melting temperature of ice, is added. This additional pd has proved to be localized at the ice surface and ranges from 0 to 150 mV; it can be directly related to the appearance and thickening of the polarized, liquidlike layer predicted by N. H. Fletcher, if we assume that a constant electric field exists in the layer interior. The preferred dipole orientation turns out to be that with the oxygens outwards. We also obtained the approximate value of 4.3 eV for the ice work function.
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.
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.
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