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.