Department of Materials Science and Engineering, University of Pennsylvania, 3231 Walnut Street, Philadelphia, Pennsylvania 19104, United States.
ACS Nano. 2011 Jun 28;5(6):4810-7. doi: 10.1021/nn2007817. Epub 2011 Apr 25.
The position of the Fermi energy level (E(F)) with respect to the energy level where the transport process occurs (transport energy level, E(T)) is an important parameter that determines the electrical properties of semiconductors. However, little attention has been devoted to investigating the position of E(F) in semiconductor nanocrystal solids, both theoretically and experimentally. In this study, we perform temperature-dependent thermopower measurements on PbTe nanocrystal solids to directly probe E(F) - E(T). We observe that as the size of the nanocrystals reduces, E(F) - E(T) increases primarily due to the widening of density of state (DOS) gap. Furthermore, by modifying the monodispersity of nanocrystals, we observe an increase in thermopower as the distribution of energy states sharpens. This work promotes a deeper understanding of thermal occupation of energy states as well as electronic transport processes in semiconductor nanocrystal solid systems.
费米能级 (E(F)) 相对于输运过程发生的能级 (传输能级，E(T)) 的位置是决定半导体电性能的一个重要参数。然而，理论和实验上都很少关注半导体纳米晶体固体中 E(F) 的位置。在这项研究中，我们对 PbTe 纳米晶体固体进行了依赖于温度的热电势测量，以直接探测 E(F) - E(T)。我们观察到，随着纳米晶体尺寸的减小，E(F) - E(T) 主要由于态密度 (DOS) 间隙的变宽而增加。此外，通过修饰纳米晶体的单分散性，我们观察到随着能态分布的变尖锐，热电势增加。这项工作促进了对半导体纳米晶体固体系统中能量态的热占据以及电子输运过程的更深入理解。
