A Review on the Laser-Assisted Flow Deposition Method: Growth of ZnO Nanostructures

Zinc oxide (ZnO) is a versatile semiconductor with major importance from the technological point of view, especially in fields of electronics and optoelectronics, due to its unique properties, namely wide band gap (3.37 eV at room temperature) and large exciton binding energy (60 meV). Moreover, this material can be grown by a large number of techniques and possess one of the richest varieties of morphologies. Due to its high vapour pressure and the fact that ZnO decomposes into atomic components near its melting temperature (1977°C) at atmospheric pressure, the vapour-based methods have been extensively explored. The method described in this paper, Laser- Assisted Flow Deposition (LAFD), has not been well explored until now and can be included in this group. This technique proved to be efficient in the production of ZnO micro/nanocrystals with different morphologies and with a very high crystalline and optical quality. This new process allows high yield of ZnO production, showing great prospects for scalable applications. In the present work, we review in detail the main growth parameters and their relationship with the produced morphologies, in addition to their influence in the structural and optical properties of the crystals. Furthermore, an assessment of the possible growth mechanisms that may be involved is reported. Some potential applications of the ZnO structures produced by LAFD were also evaluated, with focus on the photo catalysis and photovoltaic fields. Additionally, the possibility of synthesizing ZnO composite.