In Situ Scanning Tunneling Microscopy for Analysis of Surface

我们构建了一台扫描隧道显微镜(STM)，用于在电解液中的电化学条件下工作。可以同时控制隧道尖端和衬底相对于参比电极的电化学势。该装置提供了一种新的完成的可能性。恒电位条件下电解液中电极表面的原位观察。用该仪器研究了银的电化学沉积和溶解过程。在硫酸溶液中，对单晶铂(111)表面进行了电化学电位循环前后的原位扫描隧道显微镜(STM)研究。在铂(111)面上观察到的台阶通常位于几乎平行的直线上或形成接近60ﾟ的角度的方向上，这对于具有三重对称性的表面是预期的。每个台阶的高度与铂(111)面上0.238 nm的单原子台阶高度一致。在五次潜在的循环后，在梯田上清楚地观察到了随机取向的岛，其中几个原子的高度很高。用扫描隧道显微镜观察了不同半导体电极在水溶液中的表面形貌和表面电子结构。例如，研究表明，氢端的硅表面即使在水溶液中也是抗氧化性的。隧道电流-电极电位(I-E)曲线表明存在表面态。获得了光电化学氧化表面的扫描隧道显微镜图像。

We have constructed a scanning tunneling microscope(STM) for operation in electrochemical conditions in electrolyte solutions. The electrochemical potentials of the tunneling tip and the substrate with respect to a reference electrode can be simultaneously controlled. The apparatus offers a new possibility for complete. in situ observation of electrode surfaces in electrolyte solutions under potentiostatic conditions. The electrochemical deposition and dissolution of Ag have been investigated with this instrument.In situ STM was applied to single-crystal platinum(111) surfaces both before and after electrochemical potential cycling in an aqueous sulfuric acid solution. Steps observed on a Pt(111)facet were usually located on nearly parallel straight lines or on the directions forming an angle of close to 60ﾟ, as expected for a surface with threefold symmetry. The height of each step was in accord with the monatomic step height of 0.238nm on the Pt(111) surface. Randomly oriented islands a few atoms in height were clearly observed on the terraces after five potential cyclings. It was suggested that Pt adatoms produced by the reduction of the oxide are coagulated on the terraces.The topography and the surface electronic structure of various semiconductor electrodes have been examined in aqueous solutions by means of STM. It is shown, for example, that hydrogen-terminated Si surface are resistant to oxidation even in aqueous solutions. The tunneling current-electrode potential(I- E)curve suggests the existence of surface states. STM images of photoelectrochemically oxidized surfaces have been obtained.