Study of Melocular and Biomolecular Devices Working with Scanning Probe Microscpes

最近，我们成功地研制出了高效的分子光电二极管作为光电转换的分子器件。其基本思想是模仿自然光合作用中反应中心的电荷分离机制和结构功能，研制人工光电转换分子器件。然而，到目前为止，我们的分子器件的尺寸在x-y维度上是毫米到厘米的量级，尽管它们的厚度是纳米量级的。同样，我们的器件在结构和功能上具有分子器件的功能，但器件的尺寸仍然是宏观的，所开发的器件离所谓的真正的分子尺度器件还很远。在本研究项目中，我们试图开发出真正的分子光电二极管，不仅在功能上，而且在尺寸上。通过努力实现这一最终目标，我们成功地获得了以下结果：1)通过使用原子力显微镜(AFM)作为纳米级的机械加工机器来制造分子光电二极管。2)使用扫描隧道显微镜(STM)和扫描表面电位显微镜(SSPM)作为将分子器件连接到其外部电子电路的工具。3)通过设计新类型的分子和器件的结构来获得更高的分子光电二极管的效率。结合术语2)，我们还成功地研制了新型扫描近场光学显微镜(SNOM)，其中针尖-样品的分离由非接触模式AFM控制。该装置用于将分子光电二极管与外部光路光学连接。针对条款3)，通过在A-S-D单层上增加第二电子给体(D‘)单分子膜进一步提高了光致电荷分离的效率，并优化了A-S-D和H单层混合体系中S部分与H天线分子之间的能量转移。

Recently, we have succeeded in developing highly efficient molecular photodiodes as a molecular device for photo-electric conversion. The basic idea is that we try to develop artificial photo-electric conversion molecular devices by mimicking the charge separation mechanism and structural function of the reaction center in natural photosynthesis. However, so far the size of our molecular devices were in the order of mm to cm in x-y dimension in spite of their size of thickness of the order of nm.Namely, our devices functioned as molecular devices in terms of structure and function, but the size of the devices were still in macro scale and the developed devices were far from what is called "truly molecular scale devices".In the present research project, we tried to develop true molecular photodiodes not only in their function but also in their size. By the efforts to realize this final goal, we succeeded in getting the following results.1)Fabrication of molecular photodiodes by using an atomic force microscope(AFM)as a mechanical Processing machine in nm scale.2)The use of a scanning tunneling microscope(STM)and a scanning surface potential microscope(SSPM)as tools for connecting molecular devices to their external electronic circuits.3)Attainment of much higher efficiencies of the molecular photodiodes by designing new types of molecules and structure of the devices.In connection with the term 2), we also succeeded in developing novel scanning near-field optical microscope.(SNOM)in which tip-sample separation is controlled by non contact mode AFM.This device was used to connect the molecular photodiode optically from the external optical circuit.In connection with the term 3), further increase in efficiency of photo-induced charge separation by addition of a second electron donor(D')monolayr on the A-S-D monolayr and optimization of energy transfer between the S moiety and H Antenna molecules in a mixed A-S-D and H monolayr system were established.