The recent study by scientists at the Department of Energy’s Oak Ridge National Laboratory (ORNL) has shown that small changes in the isotopic content of thin semiconductor materials can significantly impact their optical and electronic properties. The research focused on molybdenum disulfide, a 2D material, and found that by synthesizing a 2D material with two isotopes of the same element but with different masses and joining them laterally in a controlled and gradual manner, they were able to observe the intrinsic anomalous isotope effect on the optical properties without the interference caused by an inhomogeneous sample.
Anomalous Isotope Effect
The anomalous isotope effect is attributed to the phonons, or crystal vibrations, scattering the excitons, or optical excitations, in unexpected ways in the confined dimensions of these ultrathin crystals. This scattering shifts the optical bandgap to the red end of the light spectrum for heavier isotopes.