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

该项目解决了与在一系列分子电子器件中使用有机材料相关的问题，以及目前使用分子材料的电子器件，如场效应管和led。各种有机金属和有机半导体（Si）表面的双光子光电发射（2PPE）研究旨在表征这些界面上的电子结构和动力学。了解界面电子结构和电子传递动力学被认为是关键的一步。主要目标和方法是利用三个良好控制的模型系统系统地建立有机-半导体和有机-金属界面的电子结构和电子转移动力学。首先，简单的芳香分子将通过间隔层被吸附到金属表面或从金属表面分离。在第二种方法中，芳香单元将以自组装单层（sam）的形式与硅表面保持一定距离。在第三种系统中，偶联低聚物的薄晶体，特别是低硫噻吩，将气相沉积在金属表面上。所有这些系统的界面电子结构将以未占据电子态的双光子光发射（2PPE）和占据电子态的单光子光发射为特征。特别重要的是2PPE，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。电子结构和电子传递动力学的实验将与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）进行表面化学和结构表征密切相关。该项目涉及具有高潜在技术相关性的材料科学主题领域的基础研究问题。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培养学生在一个基础和技术上重要的领域的研究和教育的整合。＊＊＊

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. ***