Crystalline thin film growth in anisotropic mixtures: a combined approach by experiment, theory and simulation

我们将采用实验、理论和模拟相结合的方法来研究各向异性粒子在基片上的混合物中的薄膜生长。第一个中心目标是通过在不同长度和时间尺度上用不同的理论和模拟方法分析合适的粗粒度模型，探索和解释近平衡生长和动态决定生长之间的交叉。这些研究的见解和发现将应用于不同衬底上有机半导体双组分混合物的实验系统，它们对有机分子的吸引力强度不同。这些系统与有机电子学的潜在应用有关。我们想要在表面热力学和表面相图的背景下理解这些特殊系统中的生长。这些表面相图将是理论和模拟研究的核心结果。作为第二个中心目标，我们的目标是利用各向异性材料的体积和表面热力学，通过改变衬底温度和生长速率协议来控制各向异性薄膜生长中的结构。建议的调查方法有：(i)基于基本测量理论的经典密度泛函理论，非常适合于确定各向异性混合物粗粒度模型中的体和表面热力学；（ii）晶格上和晶格外模拟，以确定相图，并覆盖薄膜生长过程中的不同时间和长度尺度；（iii）实时界面敏感散射技术(x射线反射率[XRR]，掠入射x射线衍射[GIXD]，掠射小角x射线散射[GISAXS] /漫射散射)结合生长后原子力显微镜（AFM）来表征生长结构。特别强调的是相互联系的方法：理论和离晶格模拟将建立相图并为动力学蒙特卡罗类型的更粗粒度的晶格模拟提供参数，并且将进行实验来探索相应确定的近表面相变的生长条件。因此，我们期望获得这类系统增长的全面图景。

We will investigate thin film growth in mixtures of anisotropic particles on substrates using a combined approach by experiment, theory and simulation. The first central goal is to explore and explain the crossover between near-equilibrium growth and kinetically determined growth by analyzing suitable coarse-grained models with different theoretical and simulation methods on different length and time scales. Insights and findings from these investigations shall be applied to the experimental systems of two-component mixtures of organic semiconductors on different substrates, varying in their attraction strength for the organic molecules. These systems are relevant for potential applications in organic electronics. We want to understand growth in these particular systems in the context of surface thermodynamics and surface phase diagrams. These surface phase diagrams will be a central result of the theoretical and simulation-based investigations. As the second central goal, we aim at control over structures in anisotropic film growth through variation of substrate temperature and growth rate protocol by exploiting the bulk and surface thermodynamics of the anisotropic material. The proposed methods of investigation are: (i) classical density functional theory on the basis of Fundamental Measure Theory, ideally suited for the determination of bulk and surface thermodynamics in coarse-grained models of anisotropic mixtures, (ii) on-lattice and off-lattice simulations to determine phase diagrams and to cover different time and length scales in the film growth process and (iii) real-time interface-sensitive scattering techniques (X-ray reflectivity [XRR], grazing incidence X-ray diffraction [GIXD], grazing incidence small-angle X-ray scattering [GISAXS] / diffuse scattering) combined with post-growth atomic force microscopy (AFM) for the characterization of grown structures. Special emphasis lies on the interconnected approach: theory and off-lattice simulations will establish phase diagrams and provide parameters for more coarse-grained on-lattice simulations of Kinetic Monte Carlo type, and experiments will be carried out to explore growth conditions near surface phase transitions which have been determined correspondingly. Thus we expect to obtain a comprehensive picture of growth in such systems.