The inherent large HOMO–LUMO gap of alkyl thiol (CnS) self-assembled monolayers (SAMs) has limited their application in molecular electronics. This work demonstrates significant enhancement of mechano-electrical sensitivity in CnS SAMs by external compression, achieving a gauge factor (GF) of approximately 10 for C10S SAMs. This GF surpasses values reported for conjugated wires and DNA strands, highlighting the potential of CnS SAMs in mechanosensitive devices. Conductive atomic force microscopy (cAFM) investigations reveal a strong dependence of GF on the alkyl chain length in probe/CnS/Au junctions. This dependence arises from the combined influence of molecular tilting and probe penetration, facilitated by the low Young’s modulus of alkyl chains. Theoretical simulations corroborate these findings, demonstrating a shift in the electrode Fermi level toward the molecular resonance region with increasing chain length and compression. Introducing a rigid graphene interlayer prevents probe penetration, resulting in a GF that is largely independent of the alkyl chain length. This highlights the critical role of probe penetration in maximizing mechano-electrical sensitivity. These findings pave the way for incorporating CnS SAMs into mechanosensitive and mechanocontrollable molecular electronic devices, including touch-sensitive electronic skin and advanced sensor technologies. This work demonstrates the potential of tailoring mechanical and electrical properties of SAMs through molecular engineering and interface modifications for optimized performance in specific applications.

中文翻译：

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增强自组装单层的压敏电导率


烷基硫醇 （CnS） 自组装单层 （SAM） 固有的大 HOMO-LUMO 间隙限制了它们在分子电子学中的应用。这项工作表明，通过外部压缩显着提高了 CnS SAMs 的机械-电灵敏度，使 C10S SAMs 的应变系数 （GF） 约为 10。该 GF 超过了偶联线和 DNA 链的报道值，突出了 CnS SAM 在机械敏感设备中的潜力。导电原子力显微镜 （cAFM） 研究表明，GF 对探针/CnS/Au 结中的烷基链长度有很强的依赖性。这种依赖性源于分子倾斜和探针穿透的综合影响，而烷基链的低杨氏模量则促进了这种影响。理论仿真证实了这些发现，表明随着链长和压缩的增加，电极费米能级向分子共振区域移动。引入刚性石墨烯夹层可防止探针穿透，从而产生在很大程度上独立于烷基链长度的 GF。这突出了探针穿透在最大限度地提高机械电气灵敏度方面的关键作用。这些发现为将 CnS SAMs 整合到机械敏感和机械可控的分子电子设备中铺平了道路，包括触敏电子皮肤和先进的传感器技术。这项工作展示了通过分子工程和界面修饰来定制 SAM 的机械和电气特性以优化特定应用性能的潜力。