氧化锌纳米结构的热蒸发沉积合成及生长机理

Thermal evaporation-deposition synthesis and growth mechanism of ZnO nanostructures

以ZnO粉末为原料,用N2作为载气,采用无催化辅助的热蒸发法沉积制备ZnO纳米结构,分别用X线衍射仪、扫描电镜和透射电镜对ZnO的物相、形貌和结构进行表征,并结合晶体生长理论和实验条件,对ZnO产物的形貌变化和纳米带生长方向进行研究。结果表明:离气源较近的位置到离出口较近的位置,ZnO纳米结构的形貌由连续颗粒膜逐渐向纳米带、直径大于100 nm和直径小于100 nm的纳米线变化。特别是发现ZnO纳米带除了常见的[001]生长方向外,还有[101]和[203]两种极为罕见的生长方向,这些纳米带都具有上下表面均由(±010)晶面组成的特点。ZnO产物的形貌变化是其生长过程由动力学控制为主转向热力学控制为主的结果,纳米带生长方向不同,可能与其晶核形成过程中的竞争生长有关。

Various ZnO nanostructures products were fabricated using catalyst-free thermal evaporation-deposition with ZnO powder as raw materials and N2 as carrier gas. The morphologies and structures of the obtained ZnO were characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The specific morphologies and structures of the as-synthesized nanobelts were discussed by combining the experimental results and the theory on crystal growth. The results show that the morphologies of the ZnO products change from granular films to nanobelts, then to nanowires with diameter greater than 100 nm, and finally to nanowires with diameter smaller than 100 nm, as the increase in the distance from the deposition position to the gaseous precursor. In particular, some ZnO nanobelts exhibit the unusual growth directions of [101] and [203], besides the common direction of [001], but all the nanobelts have the same upper and lower surfaces of（±010） crystallographic planes. The difference in the morphologies of ZnO products is presumed to be resulted from the change in the determining factor from kinetics to thermodynamics during crystal growth. The different growth directions may come from the competition growth of the crystal nuclei during the initial growth of the nanobelts.