Simulations of field emission from copper electrodes with inclusion of oxygen surface layer and work function changes based on first-principles calculations

Abstract

Analysis of field emission requires the inclusion of the internal potentials that shape the electronic wavefunctions and tunneling probabilities; details of the work function that are dependent on material quality and defects; and the role of the density of states (DOS) that influences the electronic supply. Here, these factors are collectively included on the basis of density functional theory to obtain predictions of field-dependent electron tunneling current densities. Results are obtained in copper for three different orientations. The DOS is predicted to be broadened by an externally applied electric field. The (100) copper is shown to yield the largest current density, and the (111) orientation is the lowest. The presence of an oxide surface monolayer is shown to increase the work function, leading to the emission of current reductions. The technique is general and can be applied to other materials (e.g., carbon fibers) that have shown promise as cathode emitters.

Contacts at the Nanoscale and for Nanomaterials

“…Furthermore, because of the high oxygen content in the sputtered films, the electrons’ film will be strongly bounded to the oxygen because of the greater electronegativity of the oxygen; as a result, it makes the thermionic emission of electrons more difficult. Theoretical calculations have shown that the workfunction of the Cu-O system is larger than that of pure copper [ 57 ]. The experimental results show that both the barrier height and the effective Richardson constant decreased.…”

Design and optimization of Cs2SnI6 based inorganic perovskite solar cell model: numerical simulation

“…The semiconductor work function (W s ) has the same definition as the metal work function. Due to the n-i-p type model structure proposed in this study, the contact potential difference between the back metal electrode and the p-type semiconductor (Cu 2 BaSnS 4 ) can be expressed as follows [71].…”

“…As the distance (D) between metals and semiconductors decreases, a space charge region will appear on the surface of the semiconductor, and surface potential (V s ) will be formed on the surface and inside of the semiconductor. Therefore, the above equation can be changed to the following form [71].…”