Extremely high negative electron affinity of diamond via magnesium adsorption

TL;DR

This study demonstrates a novel method to achieve the largest negative electron affinity on diamond surfaces through magnesium adsorption, which remains stable under various environmental conditions.

Contribution

It introduces magnesium adsorption as an effective way to induce and stabilize high negative electron affinity on diamond surfaces without high-temperature activation.

Findings

Achieved NEA of up to -2.01 eV on diamond (100) surface.

Magnesium-adsorbed diamond surfaces remain NEA after environmental exposure.

Mg adsorption differs from Li in surface chemistry and activation requirements.

Abstract

We report large negative electron affinity (NEA) on diamond (100) using magnesium adsorption on a previously oxygen-terminated surface. The measured NEA is up to $(-2.01\pm0.05)$ eV, the largest reported negative electron affinity to date. Despite the expected close relationship between the surface chemistry of Mg and Li species on oxygen-terminated diamond, we observe differences in the adsorption properties between the two. Most importantly, a high-temperature annealing step is not required to activate the Mg-adsorbed surface to a state of negative electron affinity. Diamond surfaces prepared by this procedure continue to possess negative electron affinity after exposure to high temperatures, air and even immersion in water.