From highly oriented bulk black arsenic phosphorus to well-crystallized exfoliated flakes with enhanced anti-oxidation: precise control upon chemical vapor transport

Abstract

Black arsenic phosphorus (b-AsP), as a new V group 2D material, is a promising candidate for midwave infrared photodetectors. However, the lack of high-quality b-AsP crystal synthesis strategy greatly hinders the preparation of b-AsP 2D flakes, and the susceptibility to oxidation is also a problematic issue. The lack of high-quality b-AsP synthesis strategy is attributed to the failure to find suitable conditions for the directional growth of the b-AsP (010) crystal plane. Herein, a stable strategy for the synthesis of ∼2 cm highly oriented b-AsP crystals by precise control over vapor transport process was proposed. The XRD diffraction showed that the full width at half maxima was only 0.07° in the (020) peak, and the (010) degree of orientation was up to 455.17, indicating its superior crystal quality. Impressively, the oxygen content on the surface of highly oriented b-AsP flakes was 7.7%, which was much lower than 67.5% and 63.9% of commercial black phosphorus and b-AsP-Control flakes (synthesized by the existing SnI₄–Sn system), respectively, suggesting the much higher anti-oxidation property of highly oriented b-AsP. The consistent structure of highly oriented b-AsP and the much higher oxidation resistance of substituted As atoms are the key reasons. Moreover, the characteristics of interlayer synchronous oxidation and surface hydrolysis of b-AsP were firstly revealed, which might provide guidance for the synthesis and application of b-AsP materials.