Thermal Sublimation: a Scalable and Controllable Thinning Method for the Fabrication of Few-Layer Black Phosphorus

TL;DR

This paper presents a scalable, controllable thermal sublimation method for uniformly thinning black phosphorus to few-layer thicknesses, verified by Raman spectroscopy and imaging, with precise rate control and in-situ thickness measurement.

Contribution

The study introduces a novel thermal sublimation technique for black phosphorus that achieves uniform, layer-by-layer thinning with controllable rates and in-situ thickness monitoring.

Findings

Uniform bilayer black phosphorus was produced with no micron-scale defects.

Sublimation rates were approximately 0.18 nm/min at 500 K and 1.5 nm/min at 550 K.

Established Raman-based in-situ thickness determination method.

Abstract

In this work, we reported uniform layer-by-layer sublimation of black phosphorus under heating below 600 K. The uniformity and crystallinity of BP samples after thermal thinning were confirmed by Raman spectra and 2D Raman imaging. A uniform and crystalline bilayer black phosphorus flake with an area of 180 um^2 was prepared with this method. No micron scale defects were observed. The sublimation rate of BP was around 0.18 nm / min at 500 K and 1.5 nm / min at 550 K. Both room and high temperature Raman peak intensity ratio Si/A2g vs. BP thickness relations were established for in-situ thickness determination. The sublimation thinning method was shown to be a controllable and scalable approach to prepare few-layer black phosphorus.