O在预覆盖K的Ag(110)表面的共吸附及其性质

本文用X射线光电子能谱(XPS),紫外光电子能谱(UPS),电子能量损失谱(EELS)和低能电子衍射(LEED)研究了O与预覆盖K的Ag(110)表面相互作用及其性质。在低覆盖度K下,发现有两种O的吸附态,经鉴别为溶解到表面下的O^2-和表面上吸附的O^x-增加K的覆盖度,出现分子状态的吸附物O₂^δ-,它与表面下存在的K相联系。XPS和UPS均清楚地显示出对应于三种不同吸附态的光电子发射峰。Ag(110)表面预覆盖K后的粘滞系数大大增加。K和O的共吸附引起它们彼此向Ag(110)表面下的溶解。LEED实验结果表明,清洁Ag(110)表面覆盖单层K原子后衍射图形从(1×1)变到(1×2),再吸附O后表面吸附层结构变为(2×1)。另外,结合UPS和EELS测量初步考察了O/K/Ag(110)共吸附系统的电子结构。本文还提出了一个共吸附模型来解释这些现象。 关键词：

PROPERTIES OF CO-ADSORPTION OF K WITH O ON Ag(110) SURFACE STUDIED BY XPS, UPS, EELS AND LEED

The properties of co-adsorption of K with O on the Ag(ll0) surface have been investigated with X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), electron energy loss spectroscopy (EELS) and low energy electron diffraction (LEED). It is shown that, at low potassium coverages, there are two distinct oxygen species on the Ag(ll0) which are determined as the dissolved and chemisorbed atomic oxygen species. With K coverage increasing, the molecular oxygen is developed, which is associated with subsurface K. These oxygen species peaks can be clearly distinguished from UPS as well as XPS. The initial sticking coefficient of the K precovered Ag surface for oxygen adsorption is enhanced. K and O display a mutual enhancement of surface to bulk transport. A monolayer K atoms forms (1×2) LEED pattern on the Ag(ll0) surface, which is consistent with the early results. The surface structure, however, transfers into a (2×1) ordered structure when oxygen is exposed to the surface. A mode] for co-adsorption of K with O on the Ag(ll0) is proposed.