Key Growth Parameters for the Electrodeposition of ZnO Films with an Intense UV-Light Emission at Room Temperature

The development of efficient low-temperature growth methods for the preparation of high-quality ZnO is a challenge for new generation of optoelectronic devices such as flexible UV-Iight emitting diodes (LED). We show that the UV emission at room temperature of electrodeposited ZnO is strongly influenced by the growth deposition parameters. The parameters investigated include the bath temperature, the type of anion, the deposition potential, and the oxygen and zinc ion concentrations. It is shown that working at a relatively high bath temperature and at low overvoltage dramatically increases the UV excitonic emission, whereas the visible one due to deep defects becomes negligible. The enhancement is much less marked by working at low oxygen concentration. A more intense UV emission is also observed from ZnO nanorod and nanowire arrays compared to ZnO dense films. The UV emission markedly shifts toward a higher energy when a chloride medium is used. This is assigned to a high n-type doping of ZnO giving rise to a Burstein-Moss effect. The defects possibly at the origin of high carrier concentration are discussed. The present study demonstrates that electrodeposition is a competitive low-temperature growth method for the preparation of UV LED, especially the nanowire-based ones.