The electronic band structure of a solid is a fundamental property which defines how a material will be used and integrated into device form. Electronic properties and energy levels are not universal values for a given system. For a single crystalline material, the work function value varies with crystallographic planes. In less mature technologies where fabrication quality is still in development, this becomes very apparent on the dependency of electronic/optical and structural properties on the growth and device fabrication methods. For example, atomically thin 2D materials are extremely sensitive to their surroundings (interfaces with gate dielectric, contacts etc) and bandgap renormalization is profound. Many reports of the conduction band level or electron affinity are not directly measured but are estimated from (i) measuring the valence band level and optical band gap, or (ii) calculated from theory. Inverse photoemission (IPES) has not been performed on many semiconductor systems let alone emerging quantum materials due to some measurement-related challenges.
One of the most common ways to probe the electronic structure (e.g., band structure) is by way of photoemission (PES or photoelectron spectroscopy). We apply electron-based analytical methods to directly access the electronic and chemical properties of candidate quantum systems based.