An international research team has demonstrated that the intrinsic disorder of the compound semiconductor CuInSnS₄ can be exploited to influence its optical properties. While the atomic vibrations also sense the local disorder, their response is averaged over many different local environments and therefore appears isotropic, as expected for a cubic crystal.
In contrast, the optical excitations, known as excitons, are much more sensitive to the local arrangement of atoms. Surprisingly, they show a direction-dependent optical response even though the average crystal structure is cubic. These findings shed new light on the relationship between disorder and material properties, opening new options for targeted “disorder engineering” in optoelectronic and photocatalytic devices.
Crystals are typically characterized by a periodic arrangement of atoms, in which each element occupies well-defined crystallographic sites throughout the structure. In compound semiconductors such as CuInSnS₄, a member of the adamantine chalcogenide family, the cations are ideally distributed over specific positions in the crystal structure.
