Development of Al2O3 Gate Dielectrics for Organic Thin-film Transistors

The focus of this thesis is on radio frequency magnetron sputtered aluminum oxide thin films developed for use as the gate dielectric for organic thin film transistors. The effect of top metal electrodes on the electrical characteristics of aluminum oxide metal-insulator-metal capacitors has been studied to determine an optimum material combination for minimizing the leakage current, while maximizing the breakdown field. The leakage current and breakdown characteristics were observed to have a strong dependence on the top electrode material. Devices with Al top electrodes exhibited significantly higher breakdown voltages compared to devices with Au, Ni, Cu and Ag electrodes. Introducing an Al diffusion barrier dramatically increased the breakdown field and reduced the leakage current for capacitors with Ag, Au and Cu top electrodes. The electrical characteristics were found to relate well to material properties, of the contacting metals, such as ionization potential and diffusion coefficient. ii