Highly Oriented Organic Ferroelectric Films with Single-Crystal-Level Properties from Restrained Crystallization

Device applications often require thin film growth with quasi-two-dimensional morphology and crystallization, which are not always compatible. In this work, we exploit the method of low-temperature deposition followed by restrained crystallization (LDRC) in the growth of crystalline organic molecular thin films, which tend to grow three-dimensionally with random orientations. We demonstrate that for 2-methylbenzimidazole, a molecular ferroelectric that tends to crystallize in spherulites, the quasi-two-dimensional films can be grown using LDRC with highly oriented polar axes and single-crystal-level ferroelectric properties. The crystallization process was shown to occur during the post-deposition annealing process using the in situ electrical measurements. The limited diffusion, low nucleation density, and low activation energy were found to be critical for the formation of the plate-shaped quasi-two-dimensional films. These results mark an important step in elucidating the LDRC as an effective and general approach for fabricating films with balanced crystallinity and morphology which are critical for applications.

Automated summary

In this study, we achieved thin films with quasi-two-dimensional morphology and crystallinity using low-temperature deposition followed by restrained crystallization (LDRC) method. The research on 2-methylbenzimidazole showed that quasi-two-dimensional films with highly oriented polar axes and single-crystal-level ferroelectric properties can be grown using LDRC.