# Achieving a Large Net “Negative Electron Affinity” on Diamond (100) via Molecular Oxygen and Lithium Functionalization

## TL;DR

This paper introduces a new method to create stable diamond surfaces with high electron emission potential using molecular oxygen and lithium.

## Contribution

A novel molecular oxygen oxidation method is developed to achieve a large net negative electron affinity on diamond surfaces.

## Key findings

- Molecular oxygen treatment achieves ~90% surface coverage and an NEA of −1.68 eV.
- The NEA is fully recoverable upon reactivation after slight air stability limitations.
- The method outperforms UV-ozone treatment and offers scalability for electronic applications.

## Abstract

Toward the realization
of thermally and ambient-stable diamond
surfaces with negative electron affinity (NEA), advances in surface
engineering are critical for high-performance electron-emission devices,
including thermionic and field emitters, and next-generation energy
converters. Here, we develop and systematically investigate a novel
“molecular oxygen” oxidation method for (100)-oriented
single-crystal diamond, comparing it with the benchmark UV-ozone treatment.
Using the state-of-the-art surface analysis techniques, we quantify
surface oxygen coverage and characterize the electronic structure
following lithium deposition. The molecular oxygen treatment achieves
∼90% surface coverage and produces an NEA of −1.68 eV,
outperforming UV-ozone oxidation (−1.31 eV). Although air stability
is slightly limited, the NEA is fully recoverable upon reactivation
(−1.56 eV). This study demonstrates that the new oxygen termination
provides a practical, high-performance route to optimized NEA diamond
surfaces, offering a scalable platform for next-generation electronic
and energy applications.