Structure, sodium ion role, and practical issues for β-alumina as a high-k solution-processed gate layer for transparent and low-voltage electronics.

Sodium β-alumina (SBA)-based gate dielectric films have been developed for all solution-processed, transparent and low voltage field-effect transistors (FETs). Its high dielectric constant has been ascribed to sodium (Na+) ions in the crystal structure; however, there are no published experimental results concerning the contribution of Na+ ions to the dielectric behavior, and the degree of crystallinity of the thin films. In addition, as an ionic conductor, β-alumina could give rise to some issues such as leakage current caused by Na diffusion, threshold voltage shift due to interface charge accumulation and longer response time due to slower polarization of the Na+ ions. This paper will address these issues using zinc tin oxide (ZTO) FETs, and propose possible measures to further improve SBA-based gate materials for electronic devices.