ZnO nanostructures produced by pulsed laser deposition in open air

Abstract

The paper presents a study on the fabrication of ZnO nanostructures by applying a pulsed laser deposition technique in air at atmospheric pressure (in open air). The laser ablation of a ZnO target was performed by a nanosecond Nd:YAG laser system operated at the wavelengths of 355, 532 and 1064 nm. In open air, the ablation process leads to a direct deposition of nanoparticles and nanoparticle aggregates formed in the plasma plume. The deposition of the nanostructured material on the substrate resulted in the growth of a highly porous structure. The influence was investigated of the wavelength used for ablation on the morphology, composition and optical properties of the samples. The ultraviolet ablation resulted in deposition of a structure which mainly consists of nanoparticle aggregates and separate nanoparticles. Deposition by visible light formed a highly porous structure consisting of aggregated nanoparticles. Conducting the ablation process with infrared radiation resulted in the growth of a complex 3D structure consisting of large nanoparticle aggregates. The presence of a small amount of nitrogen was detected in all samples independently of the wavelength used for ablation. It was found that the different wavelengths used for ablation lead to fabrication of ZnO structures with different morphology and different types of surface defects, which defines the photoluminescence properties of the samples. The porous structure observed in the ZnO samples, combined with their optical properties, suggests that such nanostructures could be used for efficient fabrication of sensor devices.