标题: | 硒化铅量子点阵列的穿隧能谱对尺寸之相关性 Size dependence in tunneling spectra of PbSe quantum-dot arrays |
作者: | 郑淞芳 Chen, Sung-Fang 简纹滨 Jian, Wen-Bin 电子物理系所 |
关键字: | 量子点阵列;硒化铅;电容耦合;穿隧能谱;库伦阻滞;自组装;quantum-dot array;PbSe;capacitive coupling;tunneling spectra;Coulomb blockade;self-assembled |
公开日期: | 2008 |
摘要: | 由于硒化铅的激子波耳半径,比其他二六族或三五族的材料还大(aB = 46 nm),造成溶胶法所制备之硒化铅量子点的量子局限效应更为显着,且表现出其他材料量子点所没有的特殊量子效应。不仅如此,硒化铅较大的介电常数(εm = 23),彰显电荷的屏蔽效果,并增强电容耦合效应。在过去的许多研究报告中,已指出量子阵列系统的电性是复杂,且不容易由简单理论来解释。直到目前为止,文献上对于由单颗量子点所组装而成的二维量子阵列之尺寸效应,及量子点间的电容耦合也尚未有完整的报导。 在本实验中,我们控制量子阵列的成长条件,使胶体硒化铅量子点在Au(111)表面上,自组装成不同尺寸大小的量子点阵列,并且分别在室温及液态氮温度,利用扫描穿隧电流显微镜来观测此量子点阵列的扫描穿隧能谱。在数据分析上,我们先用双穿隧接面模型,分析不同尺寸阵列的I-V曲线,进而得到样品与基板的等效电容与阵列尺寸关系。从电容的缓慢递增和饱和现象中,发现量子阵列是不能被视为单一导电岛屿,亦不能完全忽略量子点与量子点间耦合的效应。为了解是此量子点阵列的电容偶合与尺寸关系,我们将使用集体传输理论,试图了解电荷经过此阵列的传输行为。 Interdot Coulomb interactions and collective Coulomb blockade were theoretically argued to be a newly important topic and experimentally identified in semiconductor quantum dots, formed in the gate confined two-dimensional electron gas system. The developments of the cluster science and colloidal synthesis accelerated the studies of electron transport in colloidal nanocrystal or quantum-dot solids. To study the interdot coupling, various sizes of two-dimensional arrays of colloidal PbSe quantum dots are self-assembled on flat gold surfaces for scanning tunneling microscopy and scanning tunneling spectroscopy measurements at both room and liquid-nitrogen temperatures. The tip-to-array, array-to-substrate, and interdot capacitances are evaluated and the tunneling spectra of quantum-dot arrays are analyzed by the theory of collective Coulomb blockade. The current-voltage of PbSe quantum-dot arrays conforms properly to a scaling power law function. In this study, a dependence of tunneling spectra on sizes (numbers of quantum dots) of arrays is reported and the capacitive coupling between quantum dots in the arrays is explored. |
URI: | http://140.113.39.130/cdrfb3/record/nctu/#GT079621532 http://hdl.handle.net/11536/42445 |
显示于类别: | Thesis |
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