Synthesis of thin-film black phosphorus on a flexible substrate

TL;DR

This paper presents a scalable method to synthesize large-area thin-film black phosphorus on flexible substrates, enabling potential applications in flexible electronics.

Contribution

A novel room-temperature conversion process from red phosphorus to black phosphorus on flexible substrates for large-area thin films.

Findings

Successful synthesis of 40 nm thick BP film confirmed by spectroscopy and microscopy.

BP transistors show a field-effect mobility of 0.5 cm²/Vs.

Bandgap of 0.28 eV comparable to exfoliated BP.

Abstract

We report a scalable approach to synthesize a large-area (up to 4 mm) thin black phosphorus (BP) film on a flexible substrate. We first deposited a red phosphorus (RP) thin-film on a flexible polyester substrate, followed by its conversion to BP in a high-pressure multi-anvil cell at room temperature. Raman spectroscopy and transmission electron microscopy measurements confirmed the formation of a nano-crystalline BP thin-film with a thickness of around 40 nm. Optical characterization indicates a bandgap of around 0.28 eV in the converted BP, similar to the bandgap measured in exfoliated thin-films. Thin-film BP transistors exhibit a field-effect mobility of around 0.5 cm2/Vs, which can probably be further enhanced by the optimization of the conversion process at elevated temperatures. Our work opens the avenue for the future demonstration of large-scale, high quality thin-film black phosphorus.