Pacific Northwest National Lab
The energy required to liberate electrons from a surface, i.e., the work function, is a basic surface property of functional materials. In particular, low work function materials that can serve as efficient sources of electrons are of interest to low-temperature catalysis and thermionic cooling. In this talk, I will consider two approaches that can be exploited to design and realize low work function materials. First, I will discuss how the concept of electrons solvated in liquids led to the discovery of thermally stable organic and inorganic electrides (i.e., materials in which electrons behave as anions confined in a crystalline lattice host) and how their ability to donate electrons facilitates chemical processes, such as ammonia synthesis and room-temperature CO2 decomposition. An alternative approach to controlling work function is based on generating internal electrostatic fields using surface defects and polar interfaces. I will discuss experimental data and theoretical models that demonstrate how manipulating with the details of the structure and composition of surfaces and interfaces in epitaxial thin films of complex oxides can lead to significant changes of their work function values and the corresponding functional properties.