Computational Secondary Electron Emission Analysis of Ag and Au under Oxygen-Carbon Surface Contamination

When an electron hits the surface of a material, either it backscatters or it undergoes a series of random collisions and interactions with the near surface lattice and deposits its energy, causing some “secondary” electrons to have large enough energies to escape the material surface. The Secondary Electron Yield (SEY), often written as δ is defined as the ratio between the number of secondary electrons and the number of incident electrons. The emission of secondary electrons is heavily influenced by the surface conditions of the material. Understanding Secondary Electron Emission (SEE) characteristics of materials in different environmental settings has great importance when designing electronic instruments. SEE has known to have effects on electronic devices with varying levels of severity. Devices work in space are more susceptible to these effects due extreme environment they are in. Experiments to determine SEE characteristics of materials started in 1920’s. Even though today’s techniques are significantly better, these experiments are expensive and slow. The goal of this study is to develop a more cost efficient and a faster way of having insight regarding SEE for different materials, under such conditions it is difficult to simulate in an experimental setup. In this study, we choose to investigate SEE characteristics of Au and Ag for both clean and C-O layered 110 surfaces. After the estimation of required input parameters for the inelastic mean free path (IMFP), stopping power, and secondary electron yield (such as work functions, densities of states, and permittivities) using the first-principles density functional theory (DFT) software VASP, it has shown that the presence of such a layer significantly increases the SEE. The most stable C-O layer configuration for each system was identified using First Principles calculations. The calculated work functions and adsorption energies were compared to available experiments. The calculated inelastic mean free path was also compared to the experimental data, and the extended Mermin method revealed excellent agreement. The simulated SEE also agreed well with the experimental results.