Cheng-Wei Lee

Cheng-Wei Lee's picture

Ph.D. Student, Materials Science and Engineering, Graduate Research Assistant

Member since: 
Fall 2014
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Research interest: 

I have general interests in electronic and optical properties of solids, especially of semiconductors. I have been studying on non-adiabatic electron-ion dynamics via real-time time-dependent density functional theory (RT-TDDFT).  Non-adiabatic effect is neglected in the current first-principles molecular dynamics simulations, which assume Born-Oppenheimer (BO) approximation. However, BO approximation breaks down when a fast-varying potential exists in the system. For example, when a high-energy ion bombards the target materials, e.g. ion-implantation process in semiconductor industry, the system is exposed to a fast-varying potential resulting from the fast-moving ion. Inelastic collision events are known to dominate and are characterized by electronic stopping power. It has been demonstrated that such phenomena cannot be captured by first-principles molecular dynamics and time-dependent quantum mechanical treatments such as TDDFT are required.  In short, this computational approach will lead us to better understandings of how ion radiations interact with materials, which are essential to address stability issues of semiconductor device under radiation and spatial-control issues for focused-ion-beam related process.