Novel Vapor-Phase Synthesis of Flexible, Homogeneous Organic-Inorganic Hybrid Gate Dielectric with sub 5 nm Equivalent Oxide Thickness.

Organic-inorganic hybrid dielectrics have attracted considerable attention for improving both the dielectric constant ( k) and mechanical flexibility of the gate dielectric layer for emerging flexible and wearable electronics. However, conventional solution-based hybrid materials, such as nanocomposite and self-assembled nanodielectrics, have limitations in the dielectric quality when the thickness is deep-scaled, which is critical to realizing high-performance flexible devices. This study proposes a novel vapor-phase synthesis method to form an ultrathin, homogeneous, high- k organic-inorganic hybrid dielectric. A series of hybrid dielectrics is synthesized via initiated chemical vapor deposition (iCVD) in a one-step manner, where 2-hydroxyethyl methacrylate and trimethylaluminum are used as the monomer and inorganic precursor, respectively. The thickness and composition are effectively controlled to form a uniform, defect-free hybrid dielectric. As a result, the synthesized hybrid dielectric has a high- k value as high as 7 and exhibits a low leakage current density of less than 3 × 10-7 A/cm2 at 2 MV/cm, even with an equivalent oxide thickness of less than 5 nm. Furthermore, the dielectric layer shows exceptional chemical stability without any degradation in its dielectric performance and a smooth surface morphology. The dielectric layer also has good flexibility, maintaining its excellent dielectric performance under a tensile strain of up to 2.6%. Organic thin-film transistors with the developed hybrid dielectric as the gate dielectric achieved hysteresis-free transfer characteristics, with an operating voltage of up to 4 V and excellent mechanical flexibility as well. The hybrid dielectric synthesized via the iCVD process is a promising candidate for high-performance, low-power flexible electronics.