Effect of Cu, CuO, and Cu-CuO Bilayer Source/Drain Electrodes on the Performance of the Pentacene Thin-Film Transistor

Abstract

Cu, CuO, and Cu-CuO bilayer films were deposited with radio-frequency sputtering by controlling the O(2)/Ar gas flow ratio and the performance of the pentacene thin-film transistor (TFT) with these films as a source/drain (S/D) electrode was measured. With an O(2)/Ar gas flow ratio higher than 1, CuO film was obtained with a resistivity of similar to 10(5) mu cm and a work function of similar to 5.0 eV close to the highest occupied molecular orbital energy level of pentacene. Pentacene TFT with CuO film deposited at (Ar:O(2)=0:50 sccm) showed better performance than Cu film because the barrier height between the electrode and the semiconductor layer was smaller. The pentacene TFTs with CuO/Cu and Cu/CuO bilayer S/D electrodes were fabricated through the shadow mask patterning, and the CuO/Cu structure showed better performance than Cu or Cu/CuO because hole injection was through the CuO layer. It was confirmed that the edge effect with a shadow mask had an influence on the electrode pattern formation due to the infiltration of the film-forming species through the microgap.