自组装硫醇分子膜电输运特性的导电原子力显微镜研究

在Au(111)表面自组装制备了不同链长的烷烃硫醇分子膜，并利用导电原子力显微镜研究了 自组装分子膜的输运特性随外加压力的变化.结果发现分子膜的电流随压力的增加而增大， 其变化特征可以较好地用Hertz模型描述.在相同压力和电压下，通过分子膜的电流随分子链 长的增加呈指数衰减，其衰减因子先随压力的增加而减小，后逐渐趋于稳定.此外，长链分 子自组装膜的电流随压力的变化比短链分子膜更为明显.分析表明，自组装硫醇分子膜输运 特征的压力依赖性主要源于电荷在分子膜中的链间隧穿过程. 关键词：分子自组装输运特性原子力显微镜

Study of the transport properties of self-assembled alkanethiol monolayer by conduction atomic force microscopy

Self-assembled alkanethiol monolayers (SAMs) were prepared on the Au(111) substr ate. The behavior of the transport properties of SAMs under external load was in vestigated by the conduction atomic force microscopy. The current of SAM was fou nd to increase with the external load, and this property can be well characteriz ed by the Hertz model. It was also found that the conductance of SAM decreases e xponentially with the chain length of the alkanethiol molecules. The correspondi ng current decay constant β is demonstrated to decrease with the external load at first, and then becomes independent of the external load. Furthermore, the cu rrent of SAM with long chain molecules increases more apparently than that with short ones. These features all originate from the tunneling effect via nearby mo lecular chains for the charges.