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利用低温扫描隧道显微镜(STM)研究了水分子在半金属Bi(111)表面的吸附和自组装.当沉积速率比较低时,水分子主要以单体和二聚体的形式吸附在衬底表面.高分辨STM图表明,水单体平躺在衬底表面且占据on-top位.水二聚体表现为平行于衬底晶轴方向的两个亮点.当沉积速率比较高时,水分子自组装为单分散的六聚体阵列.每个六聚体表现为由3个亮点组成的三角形,其3个边分别平行于衬底晶轴方向.进一步分析表明,六聚体的3个亮点来自处于高位的3个水分子,一个H原子指向衬底上方,另一个H原子用于分子间氢键.处于低位的另外3个水分子,两个H原子参与分子间的氢键作用,因而在STM图中不易被观察到.我们认为,在半金属Bi(111)表面上水分子的自组装是一个动力学控制的生长过程.
The adsorption and self-assembly of water molecules on the semi-metallic Bi (111) surface have been investigated by cryogenic scanning tunneling microscopy (STM). When the deposition rate is relatively low, the water molecules are mainly adsorbed on the substrate surface as monomers and dimers . High-resolution STM images show that the water monomer lies on the surface of the substrate and occupies the on-top position, and the water dimer exhibits two bright spots parallel to the substrate’s crystal axis.When the deposition rate is relatively high, Self-assembly as a monodisperse hexamer array, each hexamer exhibiting a triangle composed of three bright spots with three sides parallel to the substrate crystal axis, respectively.Further analysis showed that the three bright spots Three water molecules from the high position, one H atom points to the top of the substrate and the other H atom to the intermolecular hydrogen bonds. The other three water molecules in the low position and two H atoms participate in the hydrogen bonding between the molecules, thus It is not easy to observe in the STM image, and we believe that the self-assembly of water molecules on the semi-metallic Bi (111) surface is a kinematically controlled growth process.