Shape transition in ZnO nanostructures and its effect on blue-green photoluminescence
Shape transition in ZnO nanostructures and its effect on blue-green photoluminescence
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DOI：
10.1088/0957-4484/19/44/445704
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发表时间：
2008-11-05
期刊：
影响因子：
3.5
通讯作者：
Raychaudhuri, A. K.
中科院分区：
文献类型：
--
作者：
Ghosh, Manoranjan;Raychaudhuri, A. K.
我们报道了用化学方法合成的氧化锌纳米结构在约20 nm处发生了从球形到六角形的形状转变，从而改变了蓝绿发射的光谱成分。球形纳米晶(尺寸11-18 nm)在555-564 nm范围内发射，随着尺寸的增大，发射波长向长波方向移动。另一方面，形状转变后的平衡形态的棒状和六角形小片(尺寸范围为20-85 nm)在465-500 nm附近显示出发射，并随着尺寸的增加而向更短的波长移动。形状转变还导致了体系中微观应变的松弛。我们的分析表明，可见发射来自纳米结构表面的缺陷层，该缺陷层受到形状转变的影响。蓝绿色发射光谱分量随形状变化的原因被解释为由于较小的球形粒子中没有耗尽层而引起的能带弯曲，而较大的平坦粒子中没有耗尽层。
We report that ZnO nanostructures synthesized by a chemical route undergo a shape transition at similar to 20 nm from spherical to hexagonal morphology thereby changing the spectral components of the blue-green emission. Spherically shaped nanocrystals (size range 11-18 nm) show emission in the range of 555-564 nm and the emission shifts to the longer wavelength as the size increases. On the other hand, rods and hexagonal platelets (size range 20-85 nm), which are the equilibrium morphology after the shape transition, show an emission near 465-500 nm which shifts to shorter wavelength as the size increases. The shape transition also leads to relaxation of microstrain in the system. Our analysis shows that the visible emission originates from a defect layer on the nanostructure surface which is affected by the shape transition. The change in the spectral component of the blue-green emission on change of shape has been explained as arising from band bending due to a depletion layer in smaller spherical particles which is absent in the larger particles with flat faces.