Characterization of Monolayers and Piled-up Monolayers Prepared by Vapor-Deposition of n-Alkane of Related Compounds

采用气相沉积法在石墨解解面上制备了正构烷烃(1)、脂肪酸盐（II）、烷己炔（Ill）和烷己炔（IV）的超薄膜，并用Penning电离电子能谱（PIES）和紫外光电子能谱（UPS）对薄膜进行了表征。结果表明，每一种化合物都能形成一层单层的铺层分子。UPS显示单分子层是逐层叠加的。然而，化合物i - 1 - 3对单层和多层提供了略有不同的pie。对伪pi和siguma^<2s> MOs的DOS和局部分布分析揭示了其原因：锯齿形平面的长轴和短轴在第一层与衬底表面平行，而短轴在随后的层中变得稍微平铺。利用扫描隧道显微镜（STM）研究了单层III、单层内光聚合（IMPP）制备的带状大分子（原子带状）III和单层内光聚合（IMPP）制备的布状大分子（原子布）III。证实了分子和/或烷基链的平面取向；揭示了它们的排列、与底物的通约度以及大分子的周期结构。原子带是一层一层叠加起来的。结果发现，与堆积的单层不同，多层中的烷基链取向是平坦的，尽管在叠加过程中，通过pie检测到最外层的构象不规则性。对于由单层(a)和双层（a ^2）部分组成的样品，在STM图像中也观察到不规则性：a ^2部分的覆盖层的烷基端非常不稳定，因此在每个图像中观察到的a - a ^2边界不同。然而，除了边界外，A^2部分的烷基链和聚二乙炔链的排列与A部分一样规则，但横向取向不同。

Ultrathin films of n-alkane (1), fatty acid salt (II), alkadiyne (Ill), and alkatetrayne (IV), prepared by vapor- deposition onto a cleavage plane of graphite, were characterized by Penning ionization electron spectra (PIES) and ultraviolet photoelectron spectra (UPS). The PIES showed that a monolayer of laying molecules can be formed with every compound. The UPS indicated that the monolayers are superposed layer by layer. Compounds I-Ill provided, however, slightly different PIES for the mono- and multilayers. Analysis of DOS and local distribution for pseudo-pi and siguma^<2s> MOs revealed the reason : both the long and short axes of the zigzag plane are parallel to the substrate surface in the first layer whereas the short axis becomes tiled a little in the following overlayers.A monolayer of III, that of sashlike macromolecules (atomic sashes) prepared by intramonolayer photopolymerization (IMPP) of Ill, and a single sheet of a clothlike macromolecule (atomic cloth) prepared by IMPP of IV were investigated by scanning tunneling microscopy (STM). The flat orientation of molecules and/or alkyl chains was confirmed ; their arrangement, commensuration with the substrate, and the periodic structure of the macromolecules were disclosed.The atomic sashes were superposed layer by layer. It was found that alkyl chains are oriented flat in the multilayers, unlike in the piled-up monolayers of III, although conformational irregularities in the outermost layer were detected by PIES during the superposition. The irregularities were observed in STM images as well for a specimen composed of monolayer (A) and bilayer (A^2) portions : the alkyl ends of the overlayer in an A^2 portion was so unstable that the A-A^2 boundary was observed differently in every image. Except for the boundary, however, the alkyl and polydiacetylene chains in the A^2 portion were arranged regularly as in the A portion but with different lateral orientation.