Electrical conduction mechanism of an individual polypyrrole nanowire at low temperatures

Conducting polypyrrole (PPY) nanowires doped with p-toluene sulfonamide (PTSA) were synthesized by a template-free self-assembly method. Electrical transport characteristics, i.e. current-voltage (I-V) behavior, of an individual PPY/PTSA nanowire have been explored in a wide temperature range from 300 down to 40 K. The fitting results of I-V curves indicated that the electrical conduction mechanism can be explained by the space-charge-limited current (SCLC) theory from 300 down to 100 K. In this temperature range, traps play an important role for this non-crystalline system. The corresponding trap energy and trap concentration have also been calculated based on the SCLC theory. Interestingly, there is no trap at 160 K, different from other temperatures. The obtained carrier mobility for the polymer nanowires is 0.964 cm(2) V(-1) s(-1) on the basis of trap free SCLC theory. In the temperature range of 80-40 K, little current can flow through the nanowire especially at lower voltages, however, the current follows the equation I ∞ (V/Vt-1)(ζ) at higher bias, which could be attributed to Coulomb blockade effect. Additionally, the differential conductance dI/dV curves also show some clear Coulomb oscillations.