Catalyst Research Group, Fuel Cell Cutting-Edge Center Technology Research Association (FC-Cubic TRA), 2-3-26 Aomi, Koto-ku, Tokyo 135-0064, Japan.
Langmuir. 2010 Dec 7;26(23):18097-104. doi: 10.1021/la102970r. Epub 2010 Nov 2.
Surface-enhanced infrared absorption (SEIRA)-active Au/Ti bilayer films sputter deposited on Si substrates have been prepared by an electrochemical annealing (ECA) treatment for the first time. The application of Au/Ti bilayer films on Si substrates to the spectroscopic technique is a promising alternative to the conventional technique using directly deposited Au films on Si substrates, offering excellent adhesive durability of the deposited metal films. However, Au/Ti bilayer films have never been selected for the spectroscopy technique because the films in the as-prepared state exhibit relatively smooth surface morphology: the excitation of the localized surface plasmon is vital to achieving SEIRA enhancements but could hardly be observed on the smooth morphology. It is shown by ex situ scanning tunneling microscopy measurements that the unfavorable smooth morphology of the as-prepared Au/Ti bilayer films can be modified by the ECA treatment to a reasonably rough, island-structure morphology similar to that of the conventional SEIRA-active Au films. In situ infrared absorption spectroscopy of adsorbed sulfate anions has been conducted on the Au/Ti bilayer film both before and after ECA treatment. The spectroscopy measurements demonstrate that the SEIRA activity of the film after being subjected to the treatment is significantly improved so that the technique could detect adsorbates on the film electrodes even with the submonolayer coverage. As an additional benefit, the ECA treatment has brought about a substantial increase in the fraction of Au(111) domains on the polycrystalline Au film surfaces. Accordingly, this approach enables us to prepare SEIRA-active Au films having sufficient adhesion to the Si substrates as well as the highly preferred (111) orientation.
通过电化学退火（ECA）处理，首次制备了沉积在 Si 衬底上的具有表面增强红外吸收（SEIRA）活性的 Au/Ti 双层薄膜。将 Au/Ti 双层薄膜应用于光谱技术是一种有前途的替代方法，替代了传统的直接在 Si 衬底上沉积 Au 薄膜的技术，提供了沉积金属薄膜的优异附着耐久性。然而，由于在制备状态下的薄膜具有相对光滑的表面形貌，因此从未选择 Au/Ti 双层薄膜用于光谱技术：局域表面等离激元的激发对于实现 SEIRA 增强至关重要，但在光滑的形貌上几乎无法观察到。通过原位扫描隧道显微镜测量表明，ECA 处理可以将制备的 Au/Ti 双层薄膜的不利光滑形貌修饰为类似于常规 SEIRA 活性 Au 薄膜的合理粗糙的岛状结构形貌。在 ECA 处理前后，对 Au/Ti 双层薄膜上吸附的硫酸盐阴离子进行了原位红外吸收光谱测量。光谱测量表明，经处理后的薄膜的 SEIRA 活性得到了显著提高，即使在亚单层覆盖的情况下，该技术也可以检测到薄膜电极上的吸附物。此外，ECA 处理还使多晶 Au 薄膜表面上的 Au(111)畴分数显著增加。因此，这种方法使我们能够制备具有足够附着力的 Si 衬底以及高度优选的（111）取向的 SEIRA 活性 Au 薄膜。
