DFT study of electron affinity of hydrogen terminated β-Si3N4

Despite a large amount of interests in mechanical and physical properties of silicon nitride in high temperature and high pressure applications, little has been explored in terms of using silicon nitride as secondary electron emission material. This paper reports a DFT study of the electron affinity (EA) of clean and hydrogen (H) terminated five low index β-Si3N4 surfaces:
. The clean surfaces are found to have positive electron affinity (PEA) in the range of 0.10–2.00 eV. Surfaces with H termination on N atoms always show negative electron affinity (NEA), whereas surfaces with H termination on Si atoms show PEA or NEA, depending on the type of surface. However, for all surfaces except
112¯1
, the overall effect of H termination on both N and Si is large EA shifts from − 0.9 to − 3.2 eV relative to the clean surfaces, giving rise to NEA, an effect which is similar to that seen for H termination on diamond. The different effect of H termination on the EA is understood by analyzing the geometric properties and the charge distribution of the surfaces. We propose that H terminated β-Si3N4 is a promising candidate for electron emission applications, because of its potential to obtain NEA by H termination.