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

用气相沉积方法在石墨解理面上制备了正构烷烃(1)、脂肪酸盐(II)、烷基二炔(Ill)和烷基四炔(IV)超薄膜，并用Penning电离电子能谱(PIES)和紫外光电子能谱(UPS)对其进行了表征。馅饼显示，每种化合物都可以形成产卵分子的单层。UPS分析表明，单层膜是逐层叠加的。然而，化合物I-11为单层和多层提供了略有不同的馅饼。DOS和局域分布分析揭示了原因：在第一层中，锯齿形平面的长轴和短轴都平行于衬底表面，而在随后的覆盖层中，短轴变得略有平铺。用扫描隧道显微镜(STM)观察了III单层、I11单层内光聚合(IMPP)制备的带状大分子(原子带子)的单层以及由IV的IMPP制备的单片衣状大分子(原子布)。确定了分子和/或烷基链的平面取向；揭示了它们的排列、与底物的公度以及大分子的周期结构。原子带逐层叠加。发现烷基链在多层膜中取向平坦，与III的堆积单分子层不同，尽管在叠加过程中Pies检测到最外层的构象不规则。在STM图像中也观察到了由单层(A)和双层(A^2)部分组成的样品的不规则性：A^2部分覆盖层的烷基末端非常不稳定，以至于在每个图像中观察到的A-A^2边界是不同的。然而，除了边界外，A^2部分的烷基和聚二乙炔链与A部分一样规则排列，但侧向不同。

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.