Tunable electrical conductivity—the ability to change the material’s carrier concentration over a wide range of useful values while maintaining superior mobility as well as good optical transparency—is the central technological advantage of an AOS. Although amorphous materials lack grain boundaries and periodicity, the electron transport in AOSs is more complex than in the crystalline phases: strong distortions in the metal-oxygen polyhedra and intricate structural morphology in AOSs affect the carrier mobility via composition, defects, thermal vibrations, nano-crystallinity, and lattice strain. Moreover, given many degrees of freedom in amorphous oxide, defects in AOSs have the structural, thermal, and electronic characteristics that differ fundamentally from those in the crystalline transparent conducting oxides.
In this talk, complex deposition-structure-property relationships in several prototype AOSs will be discussed. Based on a thorough comparison of the results of ab-initio Molecular Dynamics modeling, comprehensive structural analysis, and accurate density-functional calculations of the properties with systematic experimental measurements, we will outline a four-dimensional parameter space that describes complex microscopic behavior in AOSs, serves as a foundation to optimize the properties of known AOSs, and helps derive versatile design principles for next-generation transparent amorphous semiconductors.
Julia E. Medvedeva is a professor of physics and a senior investigator at Materials Research Center of Missouri University of Science and Technology. She received her PhD from the Russian Academy of Science in 2002 and worked as a pre- and post-doctoral fellow at Northwestern University. Her expertise is in first-principles density functional calculations of the structural, electronic, optical, and mechanical properties of a wide range of materials, including metal oxides and nitrides, alloys, and strongly-correlated materials. She has over 80 publications and a book chapter and is a leader in the area of transparent conducting oxides. Her research work was funded by federal and private agencies as well as industry.