Department of Chemical Engineering, Stanford University, Stanford, California 94305, USA.
Acc Chem Res. 2010 Feb 16;43(2):346-55. doi: 10.1021/ar900251s.
Organic functionalization of group IV semiconductor surfaces provides a means to precisely control the interfacial properties of some of the most technologically important electronic materials in use today. The 2 x 1 reconstructed group IV (100) surfaces in ultrahigh vacuum, in particular, have a well-defined surface that allows adsorbate-surface interactions to be studied in detail. Surface dimers containing a strong sigma- and weak pi-bond form upon reconstruction of the group IV (100) surfaces, imparting a rich surface reactivity, which allows useful analogies to be made between reactions at the surface and those in classic organic chemistry. To date, most studies have focused on single substrates and a limited number of adsorbate functional groups. In this Account, we bring together experimental and theoretical results from several studies to investigate broader trends in thermodynamics and kinetics of organic molecules reacted with group IV (100)-2 x 1 surfaces. By rationalizing these trends in terms of simple periodic properties, we aim to provide guidelines by which to understand the chemical origin of the observed trends and predict how related molecules or functionalities will react. Results of experimental and theoretical studies are used to show that relative electronegativities and orbital overlap correlate well with surface-adsorbate covalent bond strength, while orbital overlap together with donor electronegativity and acceptor electron affinity correlate with surface-adsorbate dative bond strength. Using such simple properties as predictive tools is limited, of course, but theoretical calculations fill in some of the gaps. The predictive power inherent in periodic trends may be put to use in designing molecules for applications where controlled attachment of organic molecules to semiconductor surfaces is needed. Organic functionalization may facilitate the semiconductor industry's transition from traditional silicon-based architectures to other materials, such as germanium, that offer better electrical properties. Potential applications also exist in other fields ranging from organic and molecular electronics, where control of interfacial properties may allow coupling of traditional semiconductor technology with such developing technologies, to biosensors and nanoscale lithography, where the functionality imparted to the surface may be used directly. Knowledge of thermodynamic and kinetic trends and the fundamental basis of these trends may enable effective development of new functionalization strategies for such applications.
有机官能团化的 IV 族半导体表面提供了一种精确控制当今一些最重要的电子材料界面性质的方法。特别是在超高真空条件下，2 x 1 重构的 IV 族（100）表面具有明确的表面，允许详细研究吸附物-表面相互作用。在 IV 族（100）表面重构时，形成含有强 sigma 和弱 pi 键的表面二聚体，赋予丰富的表面反应性，这使得表面反应与经典有机化学中的反应之间可以进行有用的类比。迄今为止，大多数研究都集中在单个衬底和有限数量的吸附功能团上。在本综述中，我们结合了来自几项研究的实验和理论结果，研究了与 IV 族（100）-2 x 1 表面反应的有机分子的热力学和动力学的更广泛趋势。通过用简单的周期性性质来合理化这些趋势，我们旨在提供理解观察到的趋势的化学起源和预测相关分子或官能团如何反应的指南。实验和理论研究的结果用于表明相对电负性和轨道重叠与表面-吸附体共价键强度很好相关，而轨道重叠与供体电负性和受体电子亲合性一起与表面-吸附体配位键强度相关。当然，将此类简单性质用作预测工具是有限的，但理论计算可以填补一些空白。周期性趋势所固有的预测能力可用于设计分子，以便在需要将有机分子受控地附着到半导体表面的应用中使用。有机官能团化可能有助于半导体行业从传统的基于硅的架构向其他材料（例如具有更好电性能的锗）过渡。在其他领域也存在潜在的应用，从有机和分子电子学，其中界面性质的控制可能允许将传统半导体技术与这些发展中的技术结合起来，到生物传感器和纳米尺度光刻，其中赋予表面的功能可直接使用。对热力学和动力学趋势以及这些趋势的基本基础的了解可能使这些应用的新功能化策略的有效开发成为可能。
