Bias and temperature dependent charge transport in high mobility cobalt-phthalocyanine thin films

The temperature dependent current-voltage (J-V) characteristics of highly-oriented cobalt phthalocyanine films (rocking-curve width=0.11 degrees) deposited on (001) LaAlO3 substrates are investigated. In the temperature range 300-100 K, charge transport is governed by bulk-limited processes with a bias dependent crossover from Ohmic (J similar to V) to trap-free space-charge-limited conduction (J similar to V-2). The mobility (mu) at 300 K has a value of similar to 7 cm(2) V-1 s(-1) and obeys Arrhenius-type (ln mu similar to 1/T) behavior. However, at temperatures < 100 K, the charge transport is electrode-limited, which undergoes a bias dependent transition from Schottky (ln J similar to V-1/2) to multistep-tunneling (conductivity varying exponentially on the inverse of the square-root of electric field).