Density functional theory calculations of lithium niobate surfaces and interfaces with III-nitrides

宽带隙半导体和铁电材料如铌酸锂（LiNbO 3或LN）通过直接界面的结合开启了广泛的光学和电子新器件概念。这些概念的成功实现在很大程度上取决于所形成的界面的质量。在这方面的一个主要障碍是几乎完全缺乏知识的微观结构和LN表面和界面的性能。这里提出的项目旨在详细了解LN表面和LN与III族氮化物半导体界面的原子结构和电子性质。以下建议的计算将（i）探索表面科学中未知的领域，并（ii）预计将有助于设计和优化基于LN的混合结构，如周期性极化材料。我们结合联合收割机微观电子结构计算的基础上密度泛函理论与宏观热力学。将特别注意本征缺陷的表面和界面特性的影响，以及铁电畴的振动指纹。LN表面的计算结构、振动和化学性质应用于LN衬底上GaN生长的优化和实验表面分析研究的解释，例如，μ-拉曼光谱。

The combination of wide bandgap semiconductors and ferroelectric materials like lithium niobate (LiNbO3 or LN) by means of direct interfacing opens a wide range of new device concepts both optical and electronic. The successful realization of these concepts depends largely on the quality of the interface formed. The nearly complete lack of knowledge about the microscopic structure and the properties of LN surfaces and interfaces is one major obstacle in this respect. The project proposed here aims at the detailed understanding of the atomic structure and electronic properties of LN surfaces and LN interfaces with III-nitride semiconductors. The calculations suggested in the following will (i) explore uncharted territory in surface science and are (ii) expected to help devising and optimizing LN-based hybrid structures such as periodically poled materials. We combine microscopic electronic structure calculations based on density functional theory with macroscopic thermodynamics. Particular attention will be paid to the influence of intrinsic defects on the surface and interface characteristics as well as to the vibrational fingerprints of the ferroelectric domains. The calculated structural, vibrational and chemical properties of LN surfaces shall be used for the optimization of GaN growth on LN substrates and the interpretation of experimental surface analysis studies such as, e.g., μ-Raman spectroscopy.