Department of Solid State Physics, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, India.
ACS Appl Mater Interfaces. 2009 Oct;1(10):2408-11. doi: 10.1021/am9005513.
Quantum dots (QDs) of ZnO of 2-4 nm size have been encapsulated within a SiO(2) matrix using aqueous chemically grown ZnO nanoparticles in a precursor of tetraethyl orthosilicate. The microstructure shows almost a uniform embedment of the QDs in the SiO(2) matrix, resulting in a ZnO QDs-SiO(2) composite structure. The photocurrent transients of the composite show an instant fall in the current followed by an exponential decay under ultraviolet (UV) illumination, causing negative photoconductivity (NPC), in contrast to the positive photoconductivity in only ZnO nanoparticles. The interface defect states due to the presence of the SiO(2) network around ZnO act as charge trap centers for the photoexcited electrons and are responsible for the NPC. The presence of interface-trapped charges under UV illumination has been further confirmed from capacitance-voltage measurements.
2-4nm 尺寸的氧化锌量子点（QDs）已被包裹在 SiO(2) 基质中，使用的是在正硅酸乙酯前驱体中通过水相化学生长的 ZnO 纳米颗粒。微观结构显示 QDs 几乎均匀地嵌入到 SiO(2) 基质中，形成 ZnO QDs-SiO(2) 复合结构。在紫外光（UV）照射下，复合结构的光电流瞬态表现为电流的瞬时下降，随后是指数衰减，导致负光电导（NPC），与仅在 ZnO 纳米颗粒中存在的正光电导相反。由于 SiO(2) 网络的存在，界面缺陷态充当光激发电子的电荷俘获中心，导致 NPC。从电容-电压测量中进一步证实了在 UV 照射下存在界面俘获电荷。
