Growth and Characterization of Molecular Ferroelectric Thin Films

Compared with inorganic ferroelectrics, organic ferroelectrics have advantages of low cost and low toxicity, are in increasing demand in capacitors, piezoelectric, and memory devices to reduce the environmental load. This work focuses on two types of organic molecular ferroelectric materials, croconic acid (CA) and 2-methylbenzimidazole (MBI). The work here introduces several origins of ferroelectricity in typical organics and their switching mechanism. We then investigated the nucleation, growth, and ferroelectric measurements of CA thin films. We explored the effect of substrate temperature and an external electric field on the nucleation and growth processes. The results can be used to improve the surface characteristics of ferroelectric films fabricated by the physical vapor deposition (PVD) method. Next, we focus on the growth and electric measurements of MBI thin films. We realize the fabrication of MBI thin films by PVD in vacuum. By exploiting the extreme anisotropic growth of MBI crystals, a preferential crystalline orientation along (110) plane and one polarization axis along the out-of-plane direction are acquired. Finally, in situ electrical measurements are performed to gain insights into the amorphous-to-crystalline phase transition in MBI films