Surface Potential Measurement of Organic Multi-layered Films on Electrodes by Kelvin Probe Force Microscopy

Abstract

SUMMARY We have investigated both the film thickness and sur-face potential of organic semiconductors deposited on two kinds ofelectrodes by the simultaneous observation with the dynamic force mi-croscopy (DFM)/Kelvin-probe force microscope (KFM). To clarify the in-terfacial properties of organic semiconductor, we fabricated samples thatimitated the organic light emitting diode (OLED) structure by deposit-ing bis [ N ; N ′ -(1-naphthyl)- N ; N ′ -phenyl] benzidine ( -NPD) and tris (8-hydroxyquinolinato) aluminum (Alq 3 ), respectively, on indium-tin-oxide(ITO) as anode and aluminum (Al) as cathode by the vacuum evapora-tion deposition using intersecting metal shadow masks. This depositiontechnique enables us to fabricate four different areas in the same sub-strate. The crossover area of the deposited thin films were measured bythe DFM/KFM, the energy band diagrams were depicted and we consid-ered that the charge behavior of the organic semiconductor depended onthe material and the structure.