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

用气相沉积法在石墨裂解面上制备了正构烷烃（1）、脂肪酸盐（II）、烷二炔（III）和烷四炔（IV）的超薄膜，用Penning电离电子能谱（PIES）和紫外光电子能谱（UPS）对其进行了表征。PIES表明，每种化合物都可以形成单层的层状分子。UPS表明，单分子膜是逐层叠加的。然而，化合物I-III为单层和多层提供略微不同的PIES。对伪π和siguma^MO的DOS和局部分布的分析<2s>揭示了原因：在第一层中，锯齿形平面的长轴和短轴都平行于基底表面，而在随后的覆盖层中，短轴变得略微倾斜。通过III的单层内光聚合（IMPP）制备的（原子框），用扫描隧道显微镜（STM）研究了由IV的IMPP制备的单层布状高分子（原子布）。证实了分子和/或烷基链的平面取向，揭示了它们的排列、与基底的相互作用以及大分子的周期性结构，原子链是层层叠加的。结果发现，烷基链是定向平坦的多层膜，不像在堆积的单层III，虽然在最外层的构象不规则性检测PIES在叠加。对于由单层（A）和双层（A^2）部分组成的样品，在STM图像中也观察到了不规则性：A^2部分中覆盖层的烷基末端非常不稳定，以至于在每张图像中观察到的A-A^2边界都不同。然而，除了边界之外，A^2部分中的烷基和聚二乙炔链与A部分中的一样规则地排列，但具有不同的横向取向。

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.