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Scanning electron microscopy image of palladium devices on Si/SiO2 substrate. (a) Array of several devices on a chip, each consisting on a nanowire contacted by a pair of electrodes (only the microscopic part is shown). (b) Detail of a nanowire contacted with the triangle-shaped ends of the microscopic electrodes.
Current (I)-Voltage (V) curves showing examples of the electromigration process on palladium devices. Four different devices belonging to the same chip are represented, showing the reproducibility of the process. In all four cases, the current increases linearly with the applied voltage, until the critical values (VC, IC) are reached and the current drops abruptly.
Critical voltage and current values (VC, IC) measured at the onset of electromigration of palladium nanowires in 75 devices. The graph shows two distinct groups of data. The initial total resistance values of the devices in kΩ (R0) are represented with a different code.
Critical voltage (VC) versus total device resistance values at the onset of electromigration (RC) corresponding to the palladium devices shown in Fig. 3 . The color code represents different intervals in the cross-section of the corresponding nanowires. The data corresponding to nanowires with a similar cross-section fall in a straight line of slope equal to IC.
Critical voltage and current values (VC, IC) measured at the onset of electromigration of gold nanowires in 44 devices. The initial total resistance values (R0) of the devices in Ω are represented with a different code.
Electrical characterization of two palladium devices after electromigration. (a) Current (I)-voltage (V) curve of a device with a final resistance of 100 kΩ showing characteristic steps of a metallic nanoconstriction. These features are more easily observed as peaks in the corresponding differential conductance curve. (b) I-V curve of a device with a final resistance of 10 GΩ with a typical shape of a tunneling junction. The fitted curve was calculated using the Simmons equation for tunneling current across an insulating barrier.
Experimental values of the average critical current density (JC) of palladium nanowires and their corresponding range of nanowire cross-section extracted from Fig. 4 .
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