Nayak Alpana, Suresh K A
Raman Research Institute, Sadashivanagar, Bangalore 560 080, India.
Phys Rev E Stat Nonlin Soft Matter Phys. 2008 Aug;78(2 Pt 1):021606. doi: 10.1103/PhysRevE.78.021606. Epub 2008 Aug 27.
We have studied the electrical conductivity in monolayer films of an ionic disk-shaped liquid-crystal molecule, pyridinium tethered with hexaalkoxytriphenylene (PyTp), and its complex with DNA by current-sensing atomic force microscopy (CS-AFM). The pure PyTp and PyTp-DNA complex monolayer films were first formed at the air-water interface and then transferred onto conducting substrates by the Langmuir-Blodgett (LB) technique to study the nanoscale electron transport through these films. The conductive tip of CS-AFM, the LB film, and the metal substrate form a nanoscopic metal-LB film-metal (M-LB-M) junction. We have measured the current-voltage (I-V) characteristics for the M-LB-M junction using CS-AFM and have analyzed the data quantitatively. We find that the I-V curves fit well to the Fowler-Nordheim (FN) model, suggesting electron tunneling to be a possible mechanism for electron transport in our system. Further, analysis of the I-V curves based on the FN model yields the barrier heights of PyTp-DNA complex and pure PyTp films. Electron transport studies of films of ionic disk-shaped liquid-crystal molecules and their complex with DNA are important from the point of view of their applications in organic electronics.
我们通过电流传感原子力显微镜（CS-AFM）研究了一种离子盘状液晶分子——与六烷氧基三亚苯相连的吡啶鎓（PyTp）——的单层膜及其与DNA复合物的电导率。首先在气-水界面形成纯PyTp和PyTp-DNA复合物单层膜，然后通过朗缪尔-布洛杰特（LB）技术将其转移到导电基底上，以研究通过这些膜的纳米级电子传输。CS-AFM的导电探针、LB膜和金属基底形成一个纳米级金属-LB膜-金属（M-LB-M）结。我们使用CS-AFM测量了M-LB-M结的电流-电压（I-V）特性，并对数据进行了定量分析。我们发现I-V曲线与福勒-诺德海姆（FN）模型拟合良好，这表明电子隧穿可能是我们系统中电子传输的一种机制。此外，基于FN模型对I-V曲线的分析得出了PyTp-DNA复合物和纯PyTp膜的势垒高度。从离子盘状液晶分子膜及其与DNA复合物在有机电子学中的应用角度来看，对它们的电子传输研究具有重要意义。
