DFT study of electron affinity of hydrogen terminated β-Si3N4

• This paper reports an DFT study of the electron affinity (EA) of clean and H terminated five low index β-Si3N4 surfaces.
• H termination on four out of five surfaces leads to Negative EA, an effect which is similar to H termination on diamond.
• The effect of H termination on the EA is interpreted by the geometric properties and the charge distribution of the surfaces.
• β-Si3N4 is a promising candidate for electron emission applications, because of its potential to obtain NEA by H termination.

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: 101¯0, 112¯0, 000¯1, 101¯1, and 112¯1. 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.