Electronic Structure and Electron Dynamics at Organic-Semiconductor and Organic-Metal Interfaces

该项目解决了与有机材料在一系列分子电子器件中的使用相关的问题，以及利用分子材料的FET和LED等现代电子器件。双光子光电子能谱（2 PPE）研究各种有机-金属和有机-半导体（Si）表面的目的是表征电子结构和动力学在这样的界面。理解界面电子结构和电子转移动力学被认为是关键的一步。主要目标和方法是系统地建立电子结构和电子转移动力学在有机半导体和有机金属界面使用三个良好控制的模型系统。在第一种情况下，简单的芳香分子将通过间隔层吸附到金属表面上或从金属表面分离。在第二种情况下，芳香族单元将在自组装单分子层（SAM）中与硅表面保持特定距离。在第三种系统中，共轭低聚物，特别是低聚噻吩的薄晶体将气相沉积到金属表面上。在所有这些系统中的界面电子结构的特点是双光子光电发射（2 PPE）的未占用的电子状态，结合单光子光电发射的占用状态。特别重要的是2 PPE，它允许直接探测未占据分子状态和表面之间的超快电子转移动力学。电子结构和电子转移动力学的实验将密切相关的表面化学和结构表征，使用傅里叶变换红外光谱（FTIR），X射线光电子能谱（XPS），和扫描隧道显微镜（STM）。该项目解决了材料科学领域的基础研究问题，具有很高的潜在技术相关性。这些研究有望提高我们对未来可能的纳米器件/晶体管技术的基本理解。该计划的一个重要特点是通过在一个基本和技术上重要的领域对学生进行培训来整合研究和教育。***

This project addresses issues relevant to the use of organic materials in a range of molecular electronic devices, and also to present day electronic devices such as FETs and LEDs that utilize molecular materials. Two-photon photoemission (2PPE) studies on various organic-metal and organic-semiconductor (Si) surfaces are aimed at characterizing electronic structure and dynamics at such interfaces. Understanding the interfacial electronic structure and electron transfer dynamics is considered a critical step. The primary objective and approach is to systematically establish the electronic structure and electron transfer dynamics at organic-semiconductor and organic-metal interfaces using three well controlled model systems. In the first, simple aromatic molecules will be adsorbed onto or separated from metal surfaces via spacer layers. In the second, aromatic units will be tethered at a particular distance to silicon surfaces in self-assembled monolayers (SAMs). In the third system, thin crystals of conjugating oligomers, particularly oligothiophenes, will be vapor deposited onto metal surfaces. The interfacial electronic structure in all these systems will be characterized by two-photon photoemission (2PPE) for unoccupied electronic states, in conjunction with one-photon photoemission for occupied states. Of particularly importance is 2PPE, which allows direct probing of the ultrafast electron transfer dynamics between unoccupied molecular states and the surface. The experiments on electronic structure and electron transfer dynamics will be closely correlated with surface chemical and structural characterizations using Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and scanning tunneling microscopy (STM). %%% The project addresses basic research issues in a topical area of materials science having high potential technological relevance. The studies are expected to improve our fundamental understanding of possible future nanodevice/transistor technologies. An important feature of the program is the integration of research and education through the training of students in a fundamentally and technologically significant area. ***