Detection of Charge Storage on Molecular Thin Films of Tris(8-hydroxyquinoline) Aluminum (Alq3) by Kelvin Force Microscopy: A Candidate System for High Storage Capacity Memory Cells

Retention and diffusion of charge in tris­(8-hydroxyquinoline) aluminum (Alq3) molecular thin films are investigated by injecting electrons and holes via a biased conductive atomic force microscopy tip into the Alq3 films. After the charge injection, Kelvin force microscopy measurements reveal minimal changes with time in the spatial extent of the trapped charge domains within Alq3 films, even for high hole and electron densities of >1012 cm–2. We show that this finding is consistent with the very low mobility of charge carriers in Alq3 thin films (