Measurement of ultralow injection current to polymethyl-methacrylate film

Ultralow electron/hole injection currents from an electrode to a polymethyl-methacrylate (PMMA) film can be accurately decided by measuring the slow shift in the flatband voltage of a metal-insulator-semiconductor (MIS) device. It has been found that both the electron and hole injection currents are limited by the metal/PMMA interface and can be roughly described with a modified Richardson-Schottky equation. The space charge or dipole relaxation in PMMA films has been observed as well, which induces an instant change in flatband voltage of the MIS devices. These properties are critical issues for the stability of organic thin film transistors with PMMA gate insulator. (c) 2008 American Institute of Physics.