A hybrid density functional theory investigation of silicon and germanium at the (100) diamond surface: routes to stable negative electron affinity for electron-emission applications
Year: 2025
Type: article
Abstract: Termination of the diamond (100) surface with silicon and germanium is modelled using hybrid density functional theory (DFT) for coverages up to 1 monolayer (ML). Adsorption energies and electron affinities were calculated using the B3LYP exchange-correlation functional. Calculations predict that all configurations except one possess a negative electron affinity (NEA). In general, Si adsorption results in slightly higher exothermic adsorption energies, but Ge adsorption produces surfaces with larger NEA values. Additionally, we quantify the charge transfer from the adsorbates to the diamond surface using both Mulliken and Bader’s “atoms-in-molecules” charge partitioning (QTAIM) analyses. Using Bader’s scheme, we develop a planar dipole model across the adsorbate, M (Si or Ge), and surface carbon layers, i.e., Mδ+–Csδ-, and correlate the magnitude of this dipole with the observed NEA. For Ge, an approximate linear scaling relationship is found between these two quantities. Silicon displays tentative indications of linear scaling, but shows a smaller NEA than Ge for a given surface dipole. We suggest that the suppressed NEA in the case of Si may be the result of the more negative atomic basin dipole moments for Si.
Source: Applied Surface Science
Authors: Neil L. Allan, Paul W. May
Institution: University of Bristol
Language: English
Subfield: Biomedical Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $3,930
OpenAlex ID: W4414569977