The resistivity by the two-wire method before FIB processing increased with decreasing temperature, which indicates
that the contact resistance is not negligible, even if the resistance of SB203580 the nanowire was extremely large, such as over the kilo-ohm level. Although many researchers have reported the resistivity of bismuth nanowires measured by the two-wire method, due to difficulty of the four-wire method with a very small diameter nanowire [6–12], the accuracy of the resistivities measured by the two-wire method should be carefully considered. The resistivities determined by the two-wire method using 1(I +,V +)-5(I −,V −) and 2(I +,V +)-6(I −,V −) electrodes became larger than those determined by the four-wire method, which implies that the contact resistance of the electrodes fabricated by FIB is not negligible. The temperature dependence of resistivity showed a sharp drop at very low temperature (ca. 3.7 K), which was caused by the superconductivity transition of the tungsten deposit MS275 fabricated by FIB. Although the superconductivity transition temperature of pure tungsten
is 0.01 K, it was already reported that the transition temperature of amorphous tungsten including carbon became larger than that of pure tungsten . Therefore, if the electrodes are fabricated with only the tungsten deposition, ideal superconductivity electrodes could be 3-deazaneplanocin A order applied for measurement at very low temperature. Figure 5b shows the temperature dependence of the resistivity for the bismuth nanowire measured at various electric currents from 100 nA to 300 μA using the four-wire method with the A(I +)6(I −)-2(V +)4(V −) electrodes. The inset of Figure 5b shows the dependence of the temperature variation on the current from the temperature at 100 nA (ΔT) due to joule heating calculated from the temperature coefficient and the difference in the resistance. It was selleck kinase inhibitor confirmed that obvious temperature variation was shown to be higher than 100 μA. Thus, electric
current up to 10 μA can be applied to the 521-nm-diameter bismuth nanowire for Hall measurements. It is surprising that such a high current density of 47 A/mm2 could be applied to the very narrow diameter nanoscale wire. This result indicates that almost all of the joule heat from the nanowire is absorbed into the surrounding quartz template, which possesses much larger heat capacity than the bismuth nanowire, as reported in . This is an advantage of covering the nanowire with the template because the high current makes it easier to measure the Hall voltage of the bismuth nanowire. Figure 5 Temperature dependence of the resistivity of the 521-nm-diameter bismuth nanowire. (a) Temperature dependence of the resistivity for the bismuth nanowire measured with various electrode combinations.