Synthesis of ZnO hexagonal columnar pins by chemical vapor deposition

Large-quantity of ZnO hexagonal columnar pins are fabricated on a silicon substrate by pyrolysis and oxidation of ZnS powder. We find that each ZnO pin is composed of two parts: a micron-sized hexagonal columnar base, and a tapered hexagonal stalk of 300–500 nm in diameter and 5 μm in length. The entire pin has a hexagonal cross section and grows toward the [0001] direction. Room temperature cathodoluminescence measurement shows that it has a weak near-band edge ultraviolet emission at 383 nm but a strong broad green emission at 527 nm. In sintering, ZnS decomposes to Zn and S. During the growth of these pins, Zn reacts with the incoming O₂ to form ZnO. The growth is governed by the vapor–solid mechanism.