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

针对有机大分子的分子束散射技术已经发展起来，并应用于有机薄膜生长的研究。该研究主要针对三个方面：(i)精确测量有机分子与无机表面之间的范德华相互作用。（二）脉冲分子束控制有机薄膜生长动力学。（三）寻找能控制生长动力学的催化吸附物。得到了以下结果：(i)将酞菁氢和C60脉冲分子束照射在各种无机材料上，得到表面停留时间。对衬底材料的依赖顺序为离子>金属>无定形，表明了分子与衬底相互作用的强度。非晶态衬底表面停留时间短的原因可能与“量子摩擦”有关，其中分子与表面之间电荷分布的通约是重要的。（ii）脉冲分子束用于有机薄膜的生长。研究发现，薄膜生长第一阶段的成核动力学可以通过改变脉冲宽度来控制。当分子具有较强的各向异性时，即使占空比相同，成核密度作为脉冲持续时间的函数也可以取最小值。从理论分析来看，这一发现可以用碰撞引起的迁移分子的解吸来解释。（iii）在碱卤化物上实现了Alq3的外轴生长。通过高能电子衍射的精确分析，发现该异构体为“mer”。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.