A reconstructed density of states FN theory calculation model and its application to atomically thin Fe/LaB6 spin-polarized electron source design.

Spin-polarized field emission electron sources (SP-FEES) have significant applications in high-energy physics and surface analysis. Traditional approaches for calculating electron spin polarization (ESP), which rely on multidimensional wavefunction expansions, tend to be computationally intensive and struggle with convergence issues. This paper proposes a novel method for calculating ESP by incorporating the density of states as a global parameter into the Fowler-Nordheim (FN) theory formula; it enables efficient computation of electron emission current density and ESP. The ESP of the Fe/W structure calculated using this novel method is in good agreement with the experimental results, proving the feasibility of the method. The composite structures of low work function lanthanum hexaboride (LaB6) materials with atomically thin Fe magnetic layers on their surfaces were designed for SP-FEES. The influence of the overall structural evolution of Fe/LaB6 composite structures with a 1 : 1 Fe/LaB6 layer ratio on spin polarization and electron emission properties was investigated using the proposed method. Even-layered structures demonstrate higher ESP than odd-layered ones due to quantum size effects. 1- and 2-layer Fe/LaB6 structures exhibit further enhanced ESP influenced by the superposition of quantum confinement effects at the limiting thickness. Notably, the 2-layer Fe/LaB6 structure exhibits the optimal combination of performance parameters, achieving the highest ESP of -50.40%, the lowest energy spread of 0.136 eV, and a high reduced brightness of 1.71 × 1013 A (m2 sr V)-1. This study presents a computationally straightforward and physically transparent method for calculating polarizations and demonstrates the material advantages of LaB6 in realizing low energy spread and high ESP, which facilitate the design of spin-polarized electron sources.