BAND GAP OF CUBIC AND HEXAGONAL CDS QUANTUM DOTS - EXPERIMENTAL AND THEORETICAL STUDIES
BAND GAP OF CUBIC AND HEXAGONAL CDS QUANTUM DOTS - EXPERIMENTAL AND THEORETICAL STUDIES
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发表时间：
2012
期刊：
影响因子：
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通讯作者：
N. Soltani;E. Gharibshahi;E. Saion
中科院分区：
文献类型：
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作者：
N. Soltani;E. Gharibshahi;E. Saion
分别以硫化钠和硫代乙酰胺为硫源，采用微波水热法合成了面心立方（fcc）和六方密排（hcp）结构的CdS量子点。采用X射线衍射（XRD）、透射电子显微镜（TEM）和紫外-可见分光光度法对合成的量子点进行了表征。在10~40 min范围内，随着微波辐射时间的增加，产物的平均粒径在8.5~12.5 nm之间，hcp结构的产物比fcc结构的产物大。在2.54 - 2.65 eV范围内的带隙随着微波暴露时间的增加而减小，并且具有hcp结构的颗粒比具有fcc结构的颗粒具有更大的带隙。从与时间无关的CdS体系薛定谔方程出发，用密度泛函理论（DFT）计算了CdS量子点的带隙。有很好的协议之间的测量和计算的带隙值。由于量子尺寸效应的影响，禁带宽度随颗粒尺寸的增大而减小。
CdS quantum dots of face centered cubic (fcc) and h exagonal close packed (hcp) structures were synthesized from sulphur source of sodium sulphide and thioacetamide respectively via microwave-hydrothermal method. The synthesized quantum dots were characterized using X-ray diffraction (XRD), transm ission electron microscopy (TEM) and UV-visible spectrophotometry. The average particle size in the range 8.5 - 12.5 nm increases with the increase of microwave exposure t ime from 10 to 40 min. Particles with hcp structure are larger than those with the fcc st ructure. The band gap in the range 2.54 2.65 eV decreases with the increase of microwave exposure time and the particles with the hcp structure have larger band gap than those with the fcc structure. The band gap of the CdS quantum dots were also derived from time independent Schrodinger equations for CdS system and calculated using the density functio nal theory (DFT). There is good agreement between the measured and calculated band gap values. The results also reveal that the band gap decreases with the increase of pa rticle size due to the quantum size effects.