Surface-type nonvolatile electric memory elements based on organic-on-organic CuPc-H₂Pc heterojunction

A novel surface-type nonvolatile electric memory elements based on organic semiconductors CuPc and H₂Pc are fabricated by vacuum deposition of the CuPc and H₂Pc films on preliminary deposited metallic (Ag and Cu) electrodes. The gap between Ag and Cu electrodes is 30–40 μm. For the current–voltage (I–V) characteristics the memory effect, switching effect, and negative differential resistance regions are observed. The switching mechanism is attributed to the electric-field-induced charge transfer. As a result the device switches from a low to a high-conductivity state and then back to a low conductivity state if the opposite polarity voltage is applied. The ratio of resistance at the high resistance state to that at the low resistance state is equal to 120–150. Under the switching condition, the electric current increases ∼ 80–100 times. A comparison between the forward and reverse I–V characteristics shows the presence of rectifying behavior. (paper)