STUDY OF ORGANIC THIN FILM GROWTH BY MODULATED MOLECULAR BEAM SCATTERING AND SEARCH FOR CATALITIC CONTROL FACTOR

发展了有机大分子的分子束散射技术，并将其用于有机薄膜生长的研究。这项研究针对三个主题：(I)精确测量有机分子与无机表面的范德华相互作用。(2)用脉冲分子束控制有机薄膜生长的动力学。(3)寻找能够控制生长动力学的催化吸附剂。主要研究结果如下：(1)用脉冲分子束对不同的有机材料进行辐照，获得了表面停留时间。衬底材料的依赖顺序是离子金属和非晶态，这表明分子与衬底之间的相互作用的强度。表面停留时间小的原因可能与量子摩擦有关，其中分子与表面电荷分布的公度很重要。(Ii)脉冲分子束用于有机薄膜的生长。研究发现，通过改变脉冲宽度，可以控制薄膜生长第一阶段的成核动力学。当分子具有强各向异性时，即使占空比相同，成核密度也可以取最小值作为脉冲持续时间的函数。从理论上分析，这一发现可以用碰撞诱导的迁移分子脱附来解释。(Iii)Alq3是在碱金属卤化物上实现外延生长的。通过对高能电子衍射的精确分析，发现该异构体为“聚合体”。该分子可作为有机薄膜生长的催化控制因子。

Molecular beam scattering technique for large organic molecules has been developed and used for the study of organic thin film growth. The study aimed at three subject : (i) Precise measurement of van der Waals interaction between organic molecules and inorganic surfaces. (ii) Controlling the kinetics of organic thin film growth by pulsed molecular beams. (iii) Search for catalytic adsorbate which can control the growth kinetics. The following results have been obtained.(i) Pulsed molecular beams of hydrogen phthalocyanine and C60 were irradiated on various ingoranic materials and surface residence time was obtained. The substrate materials dependence is in the order of ionic>metal>amorphous, which suggests the strength of the interaction between the molecules and the substrates. The reason why the surface residence time is small on the amorphous substrates might be related with the "quantum friction" in which the commensuration of charge distribution between the molecules and the surface is important.(ii) Pulsed molecular beams were used for organic thin film growth. It was found that the nucleation kinetics at the first stage of the thin film growth can be controlled by changing the width of the pulses. When the molecules have strong anisotropy, the nucleation density can take a minimum as a function of the pulse duration even if the duty ratio is the same. From the theoretical analysis, this finding can be explained by collision induced desorption of the migrating molecules.(iii) Epiaxial growth of Alq3 was achieved on alkali halide. The isomer has been found to be "mer" by precise analysis of high energy electron diffraction. This molecule can be a candidate for the catalitic control factor for the organic thin film growth.