The molecule 2-decyl-7-phenyl-[1]benzothieno[3,2-b][1]benzothiophene is an organic semiconductor, with outstanding properties in terms of molecular packing and its use in organic electronics. The asymmetric shape of the molecule causes a double layer crystal structure at room temperature. In this work we report its thin film growth by physical vapor deposition starting from the monolayer regime up to thick films. The films are studied in terms of their morphology, crystallographic properties, and thermal stability by atomic force microscopy and X-ray diffraction methods. It is found that the bulk molecular packing of the bilayer is formed at the initial thin film growth stage. After a thickness of one double layer, a transition into a new polymorph is observed which is of metastable character. The new phase represents a single layer phase; the crystal structure could be solved by a combination of X-ray diffraction and molecular dynamics simulations. The observed thin film growth is outstanding in terms of surface crystallization: the formation of a metastable phase is not associated with the initial thin film growth, since the first growth stage represents rather the bulk crystal structure of this molecule. Its formation is associated with cross-nucleation of one polymorph by another, which explains why a metastable phase can be formed on top of a thermodynamically more stable phase.

中文翻译：

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向热力学不稳定相的相变：苯并噻吩-苯并噻吩衍生物薄膜生长引起的交叉成核

分子 2-decyl-7-phenyl-[1]benzothieno[3,2- b][1]苯并噻吩是一种有机半导体，在分子堆积及其在有机电子学中的应用方面具有出色的性能。分子的不对称形状在室温下导致双层晶体结构。在这项工作中，我们通过物理气相沉积报告了它的薄膜生长，从单层状态到厚膜。通过原子力显微镜和 X 射线衍射方法研究薄膜的形态、晶体学性质和热稳定性。发现双层的本体分子堆积是在薄膜生长的初始阶段形成的。在一个双层厚度之后，观察到转变为具有亚稳态特性的新多晶型物。新相代表单层相；晶体结构可以通过结合 X 射线衍射和分子动力学模拟来求解。观察到的薄膜生长在表面结晶方面非常出色：亚稳相的形成与初始薄膜生长无关，因为第一生长阶段代表了该分子的整体晶体结构。它的形成与一种多晶型物与另一种多晶型物的交叉成核有关，这解释了为什么亚稳相可以在热力学更稳定的相之上形成。因为第一个生长阶段代表了该分子的整体晶体结构。它的形成与一种多晶型物与另一种多晶型物的交叉成核有关，这解释了为什么亚稳相可以在热力学更稳定的相之上形成。因为第一个生长阶段代表了该分子的整体晶体结构。它的形成与一种多晶型物与另一种多晶型物的交叉成核有关，这解释了为什么亚稳相可以在热力学更稳定的相之上形成。