Room-temperature negative differential resistance in polymer tunnel diodes using a thin oxide layer and demonstration of threshold logic

Conjugated polymers, with pi molecular orbitals delocalized along the polymer chain, are useful organic semiconductors that provide the possibility of molecular electronics for low-power organic-based memory and logic. Quantum functional devices based upon carrier tunneling processes open vistas into very efficient and low-power consumption circuitry that would be ideal for these applications. We demonstrate here strong room temperature negative differential resistance (NDR) for poly[2-methoxy-5-(2(')-ethyl-hexyloxy)-1,4-phenylenevinylene] (MEH-PPV) polymer tunnel diodes (PTD) using a thin TiO2 tunneling layer (similar to 2-8 nm) sandwiched between the MEH-PPV and the indium tin oxide anode. A key advantage is the pronounced NDR using a thick polymer layer with a large active area, circumnavigating the need for molecularly-sized junctions. Current-voltage measurements show large and reproducible NDR with a PVCR as high as 53 at room temperature. We also demonstrate basic logic circuit operation using a pair of these PTDs connected in series to form a monostable-bistable transition logic element (MOBILE) latch. (C) 2005 American Institute of Physics.