Freely suspended, van-der-Waals bound organic nm-thin functional films: mechanical and electronic characterization

TL;DR

This paper demonstrates the fabrication and characterization of ultrathin, van-der-Waals bound organic films that are freely suspended, revealing their mechanical and electronic properties without substrate influence.

Contribution

It introduces a surface-crystallization method to create freely suspended, electron-conductive organic films as thin as 6nm, with measurable mechanical and optical properties.

Findings

Suspended organic films exhibit Young's modulus of 2-13 GPa.

Films are electronically decoupled from environment, confirmed by temperature-dependent FET measurements.

Planar chiral optical activity observed in suspended membranes.

Abstract

Determining the electronic properties of nanoscopic, low-dimensional materials free of external influences is key to discovery and understanding of new physical phenomena. An example is the suspension of graphene, which has allowed access to their intrinsic charge transport properties. Furthermore, suspending thin films enables their application as membranes, sensors, or resonators, as has been explored extensively. While the suspension of covalently-bound, electronically-active thin films is well established, semiconducting thin films composed of functional molecules only held together by van-der-Waals interactions could only be studied supported by a substrate. In the present work, it is shown that by utilizing a surface-crystallization method, electron conductive films with thicknesses of down to 6nm and planar chiral optical activity can be freely suspended across several hundreds of nm. The suspended membranes exhibit a Young's modulus of 2 to 13 GPa and are electronically decoupled from the environment, as established by temperature dependent field-effect transistor measurements.