Improving Harsh Environmental Stability of Few-Layer Black Phosphorus by Local Charge Transfer

Few-layer black phosphorus (FL-BP) is a promising high-mobility semiconductor with thickness-dependent direct bandgap varying from visible to mid-infrared region. The poor stability under harsh environment, stemming from irreversible oxidization of P atoms with lone pair electrons, restricts its practical applications. Herein, an electrochemical intercalation and in situ electrochemical deposition (EI&ED) approach to produce scalable Au nanoparticles/FL-BP crystals with enhanced stability in harsh environment is developed. In this approach, the chemical reactivity of BP is significantly suppressed via the efficient local charge transfer from FL-BP to electrochemically deposited Au nanoparticles. Thus obtained Au/FL-BP based nano-devices show good stability under harsh environment, including i) high humidity of 95%, ii) immersibility in organic agents for as long as 45 days, and iii) annealing at 573 K for 9 h. In addition, compared to bare FL-BP crystals, Au/FL-BP based photodetectors present 50- and 36-fold improvement of photoresponsivity at 1550 and 1850 nm via the surface plasmonic enhancement effect. This EI&ED method can produce ultra-stable FL-BP crystals at large-scale, which resolves the crucial barriers in using FL-BP in large-scale electronic and optoelectronic devices.