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

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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.**