COMPARISON OF TUNNELING RATES IN 2 LANGMUIR-BLODGETT QUANTUM-WELL STRUCTURES DIFFERING ONLY IN BARRIER WIDTH

Langmuir-Blodgett multilayer structures were fabricated from two homologous, amphiphilic phthalocyanine molecules and differed only in interlayer separation. Sandwiching such multilayers between electrodes and using a pulsed photoconduction technique it proved possible to excite mobile carriers and to observe their motion directly as an accumulation of charge at the electrodes. From such observations the interlayer tunnelling time was measured for each structure and the differences in this parameter correlated with the change in tunnelling barrier width, which is known for each multilayer structure. Such correlation leads to a successful prediction of the barrier height and the attempt rate for tunneling in these molecules.