Excited State Relaxation Dynamics of Silicon Nanosheets using Time-dependent Density Functional Tight Binding Theory

By combining time-dependent density functional tight binding (TD-DFTB) calculations for electrons with molecular dynamics simulations, time evolution of excited state relaxation and single electron self-trapping of silicon nanosheets (SinHm) are investigated. We identify the atoms and bonds contributing to the excitations and observe the time evolution of charge density, indicating the migration of exciton from initial position to neighboring bonds. Different temperature 50K and 100K are attempted in the MD simulations, and the temperature is found to affect the electronic localization. Our simulations reveal the formation of exciton trapping and localization on certain bonds upon excitation within the timescale about 200-300fs. In summary, TD-DFTB excited state MD simulations can provide interesting insights into photoreactions and have crucial implications in modulating the exciton transport efficiency in strongly confined low-dimensional systems.