Pseudo hysteresis current loop and negative differential resistance in cluster superlattice of tellurium in zeolite

摘要

We study electron transport properties of tellurium (Te) cluster superlattice in Linde type-A zeolite. Applying a constant voltage, current-voltage (I-V) curve shows a hysteresis loop with a pseudo negative differential resistance (PNDA). The current loop and the current peak are history dependent. Under the same experimental conditions, we find that the current peak position moves to a higher voltage when the sample temperature is increased. Applying a variable voltage, I-V curve can be both monotonic and non-monotonic, depending on the frequency of the source. If a biased source is applied on the sample, the I-V curve will change with time, and eventually reach a stable state at which the current is a monotonical function of voltage. We clarify that both the current loop and peak are transient phenomena. The main transport mechanism is identified as non-resonant electron tunneling. The observed I-V characteristics can be attributed to the structure change of Te clusters inside the zeolite cages under an external electric field. The current peak can be understood as the effect of the finite transient time during which the Te cluster structure changes from one to another under an applied voltage. The temperature dependence of the peak position can be well described by many small collision assumption. With a simple mean-field-type approximation, the peak position is found to be proportional to the square root of the temperature.