Electric-field-induced semiconductor-semiconductor transition in V2O5

We report on DC I-V characteristics of two crystalline V2O5 fibers measured at room temperature over a range of currents of more than four orders of magnitude. At low currents, the resistances of the samples decrease exponentially with voltage, a behavior that can be attributed to field-enhanced tunneling. At higher currents, self-heating induces hysteretic nonlinear conductivity and small jumps toward lower resistances. In the highest range of currents, the I-V characteristics exhibit dramatic switching toward a new state with much lower resistance and memory. At first, switching could be repeated several times by cycling the sample between lower and higher currents. Eventually, a final state stabilized with smooth nonlinear I-V characteristics. The temperature dependence of the resistance of both the initial and final states is activated with similar activation energies; the voltage dependence of the resistance at low currents is also similar except for the large ratio of the pre-exponents. The final state of the samples was identified by the X-ray diffraction pattern of one of them, as the stable alpha-V2O5 phase. An interpretation of these results based on switching between metastable and stable phases of V2O5 is proposed.