Theoretical prediction of hafnium-terminated diamond (100) surface with promising negative electron affinity for electron emission applications

Controlling the chemical termination of diamond surface shows great promise in achieving negative electron affinity (NEA). In this work, we explore the feasibility of obtaining stable NEA properties by hafnium (Hf) termination on bare and oxidized diamond (100) surfaces based on swarm-intelligence structural search and first-principles calculations. The negative adsorption energies demonstrate that Hf-terminated diamond surfaces are energetically favorable. Remarkably, the lowest-energy structure at 0.25 monolayer Hf coverage on an oxidized surface has an extremely large adsorption energy of-11.15 eV, which is consistent with the largest bonding orbital population of 7.28 eV. The most negative NEA values of bare and oxidized surfaces are-3.50 and-3.19 eV at 0.25 monolayer Hf coverage, respectively. Both structures have dynamic stability, and the oxidized surface exhibits excellent thermal stability even up to 1200 K. Owing to their super stability and outstanding NEA properties, Hf-terminated diamond surfaces are suggested as promising candidate materials for electron emission applications.

Automated summary

This study explores the potential of hafnium (Hf) terminated diamond surfaces in achieving negative electron affinity (NEA). By using swarm-intelligence structural search and first-principles calculations, the researchers found that Hf-terminated diamond surfaces exhibit stable NEA properties and high thermal stability, making them promising candidate materials for electron emission applications.