Density functional theory studies of the optical properties of a beta-FeSi2 (100)/Si (001) interface at high pressure

High pressure has a significant influence on fi-FeSi2 band gaps and optical absorption tuning. In this work, using density functional theory, we investigate the effect of high pressure on the optical absorption behavior of a fi-FeSi2 (100)/Si(001) interface with some Si vacancies. As the pressure increases, the optical absorption peak down-shifts firstly, reach minimum values, and then un-shifts slowly. The electronic orbital analysis indicates that the electronic transition between the highest occupied states and the lowest unoccupied states mainly originate from Fe atoms at the interface regions. Structural analysis discloses that the Si (001) slab partially offsets the pressure exerted on the fi-FeSi2 (100) interface, but this effect will become weaker with further increasing pressure, and this physical mechanism plays an important role in its optical absorption behavior.