Black phosphorus, a promising two-dimensional material to be widely used in many areas of electronics and optoelectronics, can be prepared traditionally by high pressure or fast low-pressure transport routes. However, there lacks a general understanding of the growth mechanism and it often suffers from poor yield and high cost. In this paper, we developed a facile method to synthesize large-scale black phosphorus micro-ribbons, significantly decreasing its cost and increasing its yield, and then it can commercially produce black phosphorus. The growth process of black phosphorus micro-ribbons has been investigated systematically and its growth mechanism has been speculated, which opens up the possible opportunity to directly grow black phosphorus micro-belts even few-layered nanobelts by adjusting the growth conditions. In addition, ribbon-like few-layered black phosphorus with large area can be easily exfoliated from the grown micro-ribbons because of their smooth and large area of the cleavage plane. The ribbon-like few-layered phosphorus is beneficial to investigate the anisotropic properties of black phosphorus.

The growth of high-quality black phosphorus crystals is very important to further study the physical properties of two-dimensional black phosphorus exfoliated from bulk crystals. Herein, we designed a series of experiments to fully understand the growth of black phosphorus crystals and then explore the roles of metals (or alloys) and I elements in its growth process. Finally, we developed a general approach to grow black phosphorus in high yield with high quality and low cost. The work introduced here sheds light on the growth mechanism of black phosphorus crystals and opens up the possibility of the growth of black phosphorus thin film.

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Resistance random access memory (RRAM) is considered a promising candidate for the next generation of non-volatile memory. In this work, we fabricate metal (Ag, Ti, or Pt)/ZnO/Pt RRAM cells and then systematically investigate the effects of different top electrodes and their performance. With the formation and rupture of Ag-bridge and the shapeless oxygen vacancy filaments under a series of positive and negative bias, the set and reset processes have been successfully conducted in the Ag/ZnO/Pt device with very low work voltage, high on-off ratio, and good endurance. When applying the voltage bias to the Ti/ZnO/Pt device, the interfacial oxygen ions' migration causes the redox reaction of the conducting filament's oxygen vacancies, leading to the formation and rupture of the conducting filaments but in a relatively poor endurance. At the same time, for the Pt/ZnO/Pt device, once the filaments in the functional layer consisting of oxygen vacancies are formed, it is difficult to disrupt, resulting in the permanent low resistance state after a forming-like process. The results demonstrated that the devices with a metallic conductive bridge mechanism show much better switching behaviors than those with an oxygen ion/vacancy filament mechanism.