Jung Soon Jung, Lee Jun Young, Hong Suklyun, Kim Sehun
Department of Chemistry and School of Molecular Science (BK 21), Korea Advanced Institute of Science and Technology, Daejeon 305-701, Republic of Korea.
J Phys Chem B. 2005 Dec 29;109(51):24445-9. doi: 10.1021/jp054415o.
The adsorption and decomposition of water on Ge(100) have been investigated using real-time scanning tunneling microscopy (STM) and density-functional theory (DFT) calculations. The STM results revealed two distinct adsorption features of H2O on Ge(100) corresponding to molecular adsorption and H-OH dissociative adsorption. In the molecular adsorption geometry, H2O molecules are bound to the surface via Ge-O dative bonds between the O atom of H2O and the electrophilic down atom of the Ge dimer. In the dissociative adsorption geometry, the H2O molecule dissociates into H and OH, which bind covalently to a Ge-Ge dimer on Ge(100) in an H-Ge-Ge-OH configuration. The DFT calculations showed that the dissociative adsorption geometry is more stable than the molecular adsorption geometry. This finding is consistent with the STM results, which showed that the dissociative product becomes dominant as the H2O coverage is increased. The simulated STM images agreed very well with the experimental images. In the real-time STM experiments, we also observed a structural transformation of the H2O molecule from the molecular adsorption to the dissociative adsorption geometry.
利用实时扫描隧道显微镜（STM）和密度泛函理论（DFT）计算研究了水在Ge(100)上的吸附和分解。STM结果揭示了H₂O在Ge(100)上两种不同的吸附特征，分别对应分子吸附和H-OH解离吸附。在分子吸附几何结构中，H₂O分子通过H₂O的O原子与Ge二聚体的亲电向下原子之间的Ge-O配位键与表面结合。在解离吸附几何结构中，H₂O分子分解为H和OH，它们以H-Ge-Ge-OH构型共价结合到Ge(100)上的Ge-Ge二聚体上。DFT计算表明，解离吸附几何结构比分子吸附几何结构更稳定。这一发现与STM结果一致，STM结果表明随着H₂O覆盖度的增加，解离产物占主导地位。模拟的STM图像与实验图像非常吻合。在实时STM实验中，我们还观察到H₂O分子从分子吸附几何结构到解离吸附几何结构的结构转变。
