Fig. 1. Four different heating and cooling procedures. (a) Experiment Ⅰ; (b) experiment Ⅱ; (c) experiment Ⅲ; (d) experiment Ⅳ

Fig. 2. Samples prepared in different experiments. (a) Experiment Ⅰ; (b) experiment Ⅱ; (c) experiment Ⅲ; (d) experiment Ⅳ

Fig. 3. XRD patterns of Hittorf’s phosphorus prepared in experiments Ⅰ and Ⅱ

Fig. 4. SEM images of Hittorf’s phosphorus prepared in different experiments. (a) Experiment Ⅰ; (b) experiment Ⅱ

Fig. 5. XRD patterns of black phosphorus prepared in different experiments. (a) Experiment Ⅱ; (b) experiment Ⅲ

Fig. 6. Morphologies and EDS energy spectra of black phosphorus prepared in experiment Ⅲ. (a)(b) Metallographic images; (c)(d) SEM images; (e) EDS energy spectrum

Fig. 7. Typical Raman spectrum of black phosphorus prepared in experiment Ⅲ

Fig. 8. XPS characterization of black phosphorus

Fig. 9. TEM images of single-crystal black phosphorus prepared in experiment Ⅲ. (a) Low-resolution TEM image; (b) high-resolution TEM image; (c) SAED pattern

Fig. 10. Schematic of growth process of black phosphorus under non-vapor transport conditions