NER: Deposition of Molecular Nanostructures with Controlled in-plane Orientation

该项目是对NSF 01-157类纳米科学与工程倡议的响应。现在纳米材料的制造方法多种多样，但主要的方法依赖于自组装或先进的光刻技术。这些和其他的制造方案，特别是自组装，可以产生这样的结构，其中垂直于表面的分子取向受化学控制，赋予功能。这个项目将进一步控制取向--这样分子也可以在表面的平面上局部定向。100 nm长度尺度上的取向变化允许基于分子的相对取向获得纳米级的功能。这对于高性能分子器件来说是一个强大的概念，因为分子的性质是高度各向异性的。由于可以在局部产生更大的电场，因此纳米极化方案在定向分子方面应该比目前的极化方法有效得多。这个项目的中心任务是演示定向分子在表面上的附着。主要任务将是为几类分子(共轭聚合物、卟啉、DNA)中的每一类确定最佳方法，对取向和附着过程进行建模，并研究这些过程对场强和电极几何形状的依赖。后者将需要轻便的扫描探针显微镜。用偏振敏感近场光学显微镜(NSOM)表征分子的形貌和取向，使用与沉积取向分子相同的探针，通过光刻定义的接触获得电学性质。这个项目的新颖性和重要性源于打破了纳米结构中的面内对称性。它将产生具有新颖特性和功能的新型纳米结构。这将带来新的设备。在这个项目中，我们将用扫描探针显微镜重点研究生长过程的科学。由该沉积技术产生的新型器件的最终制造将需要更快的制造方法。一旦了解了工艺，大规模制造的前景是好的，我们已经定义了一条可能的路线，通过这些研究获得了基于掩模的技术。

This project was received in response to Nanoscale Science and Engineering initiative, NSF 01-157, category NER. Nanoscale materials are now fabricated by a variety of means, but the dominant methods rely on self-assembly or advanced lithography. These and other fabrication schemes, especially self-assembly, can create structures in which the molecular orientation perpendicular to the surface is controlled by the chemistry, conferring the functionality. This project will take control of orientation one step further - so that the molecules can also be locally oriented in the plane of the surface. Variations of the orientation on a 100 nm length scale permits nanoscale functionality based on the relative orientation of molecules to be obtained. This is a powerful concept for high performance molecular devices, since the properties of molecules are highly anisotropic. The 'nanopoling' scheme should be much more effective at orienting molecules than current poling methods due to the larger electric field that can be generated locally. The central task of this project is to demonstrate the attachment of oriented molecules to a surface. Major tasks will be the identification of the best method for each of a few classes of molecules (conjugated polymers, porphyrins, DNA), to model the orientation and attachment processes, and to study the dependence of these processes on field strength and electrode geometry. The latter will require the facile scanning probe microscope. Topography and orientation of the molecules is characterized with polarization-sensitive near-field optical microscopy (NSOM) utilizing the same probe as deposited the oriented molecules, and the electrical properties are obtained via lithographically-defined contacts. The novelty and importance of this project evolves from the breaking of the in-plane symmetry within the nanostructures. It will result in new types of nanostructures with novel properties and functionality. This will lead to new devices. In this project we will focus on the science of the growth process with a scanning probe microscope. Ultimate usage for fabrication of the novel devices engendered by this deposition technique will require much faster fabrication methods. The prospects for large-scale fabrication once the processes are understood are good, and we have defined a possible route to a mask-based technology resulting from these studies.