Alternative Face-on Thin Film Structure of Pentacene
Alternative Face-on Thin Film Structure of Pentacene
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DOI：
10.1038/s41598-018-37166-6
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发表时间：
2019-01-24
影响因子：
4.6
通讯作者：
Hasegawa, Takeshi
中科院分区：
文献类型：
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作者：
Shioya, Nobutaka;Murdey, Richard;Hasegawa, Takeshi
并五苯作为有机薄膜晶体管的基本材料多年来备受关注。已知并五苯在薄膜中形成高度有序的结构，其中分子长轴垂直于基底表面排列，即端上取向。另一方面，在以SiO2为代表的惰性基板上从未发现分子平面与基板平行的正面取向薄膜。因此，长期以来，人们一直认为面朝取向仅在金属单晶等特定基材上产生。在本研究中，首先通过可见光和红外 p 偏振多角度入射分辨率光谱 (pMAIRS) 以及二维掠入射 X 射线衍射 (2D-GIXD) 确定了 SiO2 表面上生长的正面取向。多种技术的结合很容易表明，面对面阶段无疑是主要组成部分。当薄膜生长受到动力学限制以防止转变为热力学稳定结构（即端上取向）时，获得正面薄膜。这个概念对于控制一般有机半导体薄膜中的分子取向很有用。
Pentacene attracts a great deal of attention as a basic material used in organic thin-film transistors for many years. Pentacene is known to form a highly ordered structure in a thin film, in which the molecular long axis aligns perpendicularly to the substrate surface, i.e., end-on orientation. On the other hand, the face-on oriented thin film, where the molecular plane is parallel to the substrate, has never been found on an inert substrate represented by SiO2. As a result, the face-on orientation has long been believed to be generated only on specific substrates such as a metal single crystal. In the present study, the face-on orientation grown on a SiO2 surface has first been identified by means of visible and infrared p-polarized multiple-angle incidence resolution spectrometry (pMAIRS) together with two-dimensional grazing incidence X-ray diffraction (2D-GIXD). The combination of the multiple techniques readily reveals that the face-on phase is definitely realized as the dominant component. The face-on film is obtained when the film growth is kinetically restricted to be prevented from transforming into the thermodynamically stable structure, i.e., the end-on orientation. This concept is useful for controlling the molecular orientation in general organic semiconductor thin films.