金刚石表面的分子反应

The properties of diamond-based materials can be tuned by the chemical modification of the surface, providing important potentials in the applications of new semiconductor and bio-compatible materials. It has been a long-term challenge on how to modify the chemical properties of diamond surfaces effectively and conveniently. To attack this challenge, we propose the strategy of using surface reactions of simple organic molecules to modify the diamond surface chemically. We shall use haloalkanes and unsaturated organic molecules as two model class of reagents to produce halogens and alkyls on the diamond surface, respectively. By means of scanning tunneling microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, temperature programmed desorption, and theoretical modeling, we shall examine the adsorption and the subsequent reaction (pathways, elementary steps, etc) both in-situ and quantitatively, so as to reveal the representative molecular mechanisms for surface halogenation and addition reactions. Further, we shall use bi-functional reagents, unsaturated organic halides, to study and control the competition between surface halogenation and addition. The goal of the proposed research is to develop a general strategy to chemically modify the diamond surfaces in a rational and green manner.

金刚石的材料性质可通过对其表面的化学修饰进行调节，在新型半导体与生物兼容材料上均有重要的应用价值。如何高效、便捷地对金刚石表面进行化学修饰一直是该领域研究的重点与难点。针对这一课题，本项目拟将有机小分子引入金刚石表面，通过其表面的分子反应进行化学修饰。针对表面卤化与烃基化这两类修饰目标，申报人团队拟选择卤代烃与不饱和烷烃这两类具有不同官能团的有机分子为模拟反应物，通过扫描隧道显微镜、原子力显微镜、X射线光电子能谱、程序升温谱以及理论模拟计算等多种方法，对其在金刚石表面的分子吸附、反应路径以及动力学基元过程进行原位的定量研究，从而揭示表面卤化与加成反应的典型机理。对于具有双官能团的不饱和卤代烃，申报人团队拟侧重研究如何控制卤化与加成反应的相互竞争，从而实现对反应模式的选择性调控。本项目拟通过上述系统研究建立具有普适性的表面分子反应策略，以实现对金刚石表面理性、绿色的化学修饰。

金刚石是重要的宽禁带半导体材料，可通过表面化学修饰调控其理化性质。本项目通过实验与理论相结合的手段，研究金刚石表面一系列化学修饰过程（氮化、氢化、烃基化、卤化等）所涉机理，归纳其中所蕴含的构效关系。具体结果如下： (a）模拟本征金刚石(001)表面氮化所涉物种的吸附结构、能量、正则振动模式及引起的衬底芯能级变化，解析吸附物种/吸附物种、吸附物种/衬底的相互作用。(b)以氢化金刚石(001)为例，探索表面氢化对金刚石氮化的影响，发现氢化金刚石表面氮二聚体以平躺和垂直两种形式存在，其热稳定性较本征金刚石表面的氮物种大大增强。(c)以氢化金刚石(111)为例，探索不同金刚石晶面对表面氮化的影响，发现氮化后的表面物种不再以氮二聚体存在，而是倾向于形成氮氢物种。(d)以银为例，探索金属物种在金刚石(001)表面扩散迁移的微观机理。(e)以环戊烯为例，解析不饱和烃与金刚石（001）表面加成反应的路径、能垒与过渡态。（f）以C4F9I为例，探索金刚石（001）表面卤代烷烃的分子吸附与解离吸附所经历的表面物种的结构、键合与能量。