Abstract
Single-crystal hexagonal pyramids of zinc: blende ZnS are fabricated by facile thermal evaporation in an ammonia atmosphere at 1150 degrees C. It is found that ZnS pyramids grow along the [111] crystal axis and possess a sharp tip with a diameter of similar to 10 nm and a micrometer-sized base. The structural model and growth mechanism are proposed based on crystallographic characteristics. This unique ZnS pyramid structure exhibits a low turn-on field (2.81 V mu m(-1)), a high field-enhancement factor (over 3000), a large field-emission current density (20 mA cm(-2)), and good stability with very small fluctuation (0.9%). These superior field-emission properties are clearly attributed to the pyramid morphology, with micrometer-sized bases and nanotips, and high crystallinity. Moreover, a stable UV emission of 337 nm at room temperature is observed and can be ascribed to the band emission of the zinc blende phase. These results suggest that the ZnS hexagonal pyramids can be expected to find promoting applications as field emitters and optoelectronic devices.