Transfer-free synthesis of large-area 2D boron films on non-wetting liquid gallium substrate

Abstract

Two-dimensional (2D) boron films have been studied for their attractive physical and chemical properties in diverse technologies. However, the synthesis of large scale and high-quality boron films is still challenging, which limit its applications in high-performance devices. In this work, thin 2D boron films have been synthesized by chemical vapor deposition (CVD) on non-wetting liquid gallium (Ga) spheres by using boron and boron oxide powders as solid sources. The thin films were directly exfoliated onto SiO2/Si substrates to prepare smooth and uniform boron films by means of mechanical exfoliation method. The peak of boron at 618 cm−1 wave number is obtained by Raman characterization and the boron peak at 188.8 eV is obtained by XPS, which indicates that the film is elemental boron film. By controlling the intercalation chemistry, we obtained large-area 2D polycrystalline boron films with a thickness of 0.8 nm by using transfer-free Synthesis, which avoids the introduction of impurities. The research promotes the application of 2D boron thin film materials in electrical and optical devices.