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 tetrapodshaped nano ZnO crystals. The synthesised material exhibits higher porosity, providing significant advantages in gas sensor fabrication.