Physical Chemistry I, Department of Chemistry, Ruhr-University Bochum, 44780 Bochum, Germany.
Phys Chem Chem Phys. 2010 May 7;12(17):4317-23. doi: 10.1039/b924230a. Epub 2010 Feb 3.
The charge transport across a pentacene/SAM interface has been studied by scanning tunnelling spectroscopy (STS) as a function of temperature and film thickness in order to obtain information on the transport mechanisms and in particular on the importance of interfacial OH-groups on n-transport in organic semiconductors. The current-voltage (I-V) characteristics of pentacene thin films deposited on a mercaptoundecanol self-assembled monolayer (SAM) on Au(111) reveal an asymmetric behaviour. At positive sample bias the onset currents shift towards higher voltages for decreasing temperatures, whereas such changes are not seen at negative bias. For lower temperatures, the variation of current onset with layer thickness is absent. These observations are explained by OH-groups at the SAM-surface effectively acting as charge traps. When electrons are caught in these traps at the organic-organic interface, charge transport is severely affected. Imaging of the SAM after loading the traps suggests that the attachment of electrons to the OH-groups exposed at the organic surface is a reversible process.
通过扫描隧道光谱（STS）研究了 pentacene/SAM 界面的电荷传输，作为温度和薄膜厚度的函数，以获取有关传输机制的信息，特别是关于有机半导体中 n 传输中界面 OH 基团重要性的信息。在 Au(111)上的巯基十一醇自组装单层（SAM）上沉积的 pentacene 薄膜的电流-电压（I-V）特性表现出不对称行为。在正偏压下，随着温度的降低，起始电流向更高的电压移动，而在负偏压下则没有这种变化。对于较低的温度，电流起始与层厚度的变化不存在。这些观察结果可以通过 SAM 表面的 OH 基团有效地作为电荷陷阱来解释。当电子在有机-有机界面处的这些陷阱中被捕获时，电荷传输会受到严重影响。对陷阱加载后的 SAM 进行成像表明，电子与暴露在有机表面的 OH 基团的附着是一个可逆过程。
