Direct Observation of Orbital Hybridization Evolution in BAs.

Boron arsenide (BAs) has a coefficient of thermal expansion comparable to that of common semiconductor materials like silicon, which helps prevent device damage or performance degradation due to thermal expansion mismatch. Understanding the evolution of electron orbital hybridization near the Fermi level as temperature varies is vital for elucidating the thermal and electrical properties of BAs crystals. Despite its significance, this topic has not been reported until now. In this study, ultraviolet photoelectron spectroscopy (UPS) was employed to measure the occupied electronic states near the Fermi level in BAs. The compositional ratio of the σ and π bands comprising the electronic states, as well as their binding energies, was found to vary with temperature. Density functional theory (DFT) calculations reveal that temperature-dependent orbital hybridization can be attributed to the evolution of phonon scattering strength.