Nanoscale Materials Defect States Imaging and Quantitative Interpretation

Direct imaging and simultaneous quantitative identification of chemical states of defects at atomic spatial resolution offer significant insight essential for emerging nanomaterials (topological insulators, hetero-nanostructures, etc.) development. In this work, a surface photoabsorption technique will be presented where secondary electron (SE) excited states get modified via injected photons. The energy associated with photon absorption in exciting the SE energy states is selective to the electronic band structure and the energy spectra of the injecting photon, which yields an energy signature of local materials state and hence the materials topology signature and related nanoscale materials defect distribution. The technique combines the high selectivity of low energy photo-excitation (laser) beam in SEM to selectively photo-excite the surface states to alter the inelastic scattering cross section of secondary electrons. This generates signatures specific to the surface states in the secondary electron (SE) yield of SEM. The atomic or molecular materials defects strongly influences the thermal (phonon) and electronic transport characteristics, which consequentially affect the nano scale thermal device performance. For quantitative interpretation of excited data, the computational framework for a reliable energy loss function (ELF) at low energy and finite wave number will be discussed. In addition, the atomic and energy state of 2D materials heterostructures and its effect in device performance will be discussed.