Band gap and electronic structure of 2D-systems, spinelectronics and ultra-hard materials studied with synchrotron-based soft X-ray Spectroscopy and Density Functional Theory

物质的外层电子和不太强的电子决定了大多数材料的性质，包括颜色、化学键能力、硬度、磁性、带隙、电子结构以及对导电和导热甚至超导的催化活性。有了测量、建模和理解材料外部电子的手段，我们就可以理解和调整重要的物理性质。这项研究将使用同步辐射软X射线光谱分析技术，在三个重点领域回答有关新材料结构的关键问题：*1.LED照明应用的超硬材料：硬度本质上很难测量，因此理论模型可以帮助设计比钻石(已知最硬材料)更硬的材料。我们将进一步改进我们的模型，将材料的硬度与其带隙联系起来，我们将对该模型进行实验测试，目标是将这些材料应用于LED照明应用。*2.用于新存储设备和高性能计算的自旋电子材料：*我们将找到新的适用于使用电子自旋和电荷存储信息的应用的铁磁半导体。如果大规模实现，自旋电子学将通过允许更快的处理速度和更高的存储密度来彻底改变计算能力。*3.二维(2D)材料：石墨烯的生长--一种2D孤立的石墨平面--及其在当前基于硅的纳米技术中的集成面临着几个挑战，其中一个挑战是没有半导体器件应用所需的带隙。2D半导体对于纳米级器件应用以及超级电容器和光伏器件都是非常理想的。我们的工作目标是：i)改变石墨烯的性质以产生带隙；ii)开发另一种2D半导体材料，如石墨烯类似物“硅烯”，其中的碳原子被硅取代。能带结构和带隙被预测为取决于石墨层的堆积层数、堆积顺序和电场。其他重要的问题包括确定合适的衬底，硅烯可以在其上保持带隙或正确的层结构。*总体而言，同步加速器测量与最新计算的比较将提供非常详细的见解，并有助于设计具有定制的电子、光学、磁性和化学性质的新材料，用于工业、医疗和电子环境。**

The outer and less strongly bound electrons of matter are responsible for most material properties including color, chemical-bonding capacity, hardness, magnetism, band gap, electronic structure, and catalytic activity to electrical and heat conductivity and even super-conductivity. Having the means to measure, model, and understand the outer electrons of a material gives us the key to understanding and tailoring important physical properties. This research will employ soft X-ray spectroscopy with synchrotron radiation to answer key questions concerning the structure of new materials in 3 areas of focus:***1. Ultra-hard materials for LED lighting applications: Hardness is inherently difficult to measure and therefore theoretical models can help to design materials that are harder than diamond (the hardest material known). We will further refine our model that relates the hardness of a material and its band gap, we will test the model experimentally with the goal to apply these materials in LED lighting applications. ******2. Spinelectronic materials for new storage devices and high performance computing:***We will find new suitable ferromagnetic semiconductors for applications that use the electron spin and charge to store information. If realized on a large scale, spintronics will revolutionize computing capabilities by allowing faster processing speed and higher storage density.******3. Two dimensional (2D) materials: The growth of graphene - a 2D single isolated plane of graphite - and its integration in current silicon-based nanotechnology is facing several challenges, one having no band gap which is needed for semiconductor device applications. A 2D semiconductor would be extremely desirable for nanoscale device applications as well as supercapacitors and photovoltaic devices. Our work aims to: i) alter the properties of graphene to create a band gap and ii) develop another 2D semiconducting material such as the graphene analogue "silicene", in which the carbon atoms are replaced by silicon. Band structure and band gap are predicted to depend on the number of stacked layers, stacking sequence, and electric fields across the graphite layers. Other important questions include identification of a suitable substrate on which silicene could maintain a band gap or the correct layer structure.******Overall, the comparison of synchrotron measurements with state-of-the-art calculations will provide very detailed insight and facilitate the design of new materials with tailored electronic, optical, magnetic, and chemical properties for use in industrial, medical and electronic contexts.**