Using neutral atoms to study in situ damage on organic materials

We use helium atoms excited in a metastable state to characterize in real-time damage induced on organic materials due to electron impact. More specifically, we used a self-assembled monolayer of 11-bromo-1-undecanethiol on gold-coated silicon exposed to 30 eV electron beam. After each electron beam exposure, we probed the sample using helium atoms in ³S₁ state that is 19.8 eV above the ground state. Once the helium atoms encounter the sample's surface, they de-excite and the excess energy causes electron emission from the surface. By measuring the kinetic energies of the emitted electrons we can determine chemical changes that occurred between each electron beam exposure. Due to the fact that metastable helium atoms barely damage our sample while being probed, this technique ensures that any chemical changes we observe are solely due to the electron beam impact. This project is part of a broader effort to develop a neutral atom microscope.