Fabrication of tetrapod nanomaterials by thermal evaporation at atmospheric pressure without crystallisation

Abstract

In this study, we propose a method for fabricating nano ZnO tetrapod materials synthesised through the thermal evaporation of Zn powder mixed with C at a 1:1 ratio under non-crystalline seed conditions and air pressure. The Zn powder is oxidised at 1,050ºC, developing nano ZnO crystals with a uniform structure. Each centre develops four nanowires, forming a tetrapod shape. The diameter of each nanowire is about 30-40 nm; the length is from 200 to 1,000 nm. A more specific study of the material structure by X-ray diffraction diagram shows that the sample has a typical hexagonal crystal structure. Laser-excited fluorescence spectroscopy using a He-Cd laser (325 nm) shows that the emission spectrum consists of two regions of 381 nm and 514 nm, characteristic of a ZnO semiconductor. These results prove that there is a certain necessary ratio of zinc and oxygen in the vapour phase to create tetrapod shaped nano ZnO crystals. The synthesised material exhibits higher porosity, providing significant advantages in gas sensor fabrication.