Investigation of space charge at pentacene/metal interfaces by a near-field scanning microwave microprobe

Space charge properties at the interface of pentacene thin films on gold (Au) and aluminum (Al) surfaces were investigated by using a near-field scanning microwave microprobe. The space charge was observed by measuring the microwave reflection coefficient S-11 and compared with the result of a Kelvin-probe method. The obtained Delta S-11 of the pentacene thin films on Al increased as the pentacene film thickness increased due to the accumulation of negative space charges. Using the pentacene field effect transistor with a Au source, hole injection from the Au electrode into pentacene with varying drain source biasing was imaged by near-field scanning microwave microprobe. (C) 2007 American Institute of Physics.