Surface transfer doping of hydrogen-terminated diamond probed by shallow nitrogen-vacancy centers

TL;DR

This study investigates the factors influencing surface transfer doping in hydrogen-terminated diamond by analyzing shallow nitrogen-vacancy centers, revealing that surface acceptor density, not work-function difference, primarily governs band bending and conductivity.

Contribution

It demonstrates that surface acceptor density, rather than work-function difference, controls band bending in hydrogen-terminated diamond, advancing understanding of surface transfer doping mechanisms.

Findings

Conductivity decreases with increased nitrogen implantation fluence.

Negative NV center signals correlate with reduced surface conductivity.

Band bending is primarily limited by surface acceptor density.

Abstract

The surface conductivity of hydrogen-terminated diamond is a topic of great interest from both scientific and technological perspectives. This is primarily due to the fact that the conductivity is exceptionally high without the need for substitutional doping, thus enabling a wide range of electronic applications. Although the conductivity is commonly explained by surface transfer doping due to air-borne surface acceptors, there remains uncertainty regarding the main determining factors that govern the degree of band bending and hole density, which are crucial for the design of electronic devices. Here, we elucidate the dominant factor influencing band bending by creating shallow nitrogen-vacancy (NV) centers beneath the hydrogen-terminated diamond surface through nitrogen ion implantation at varying fluences. We measured the photoluminescence and optically detected magnetic resonance (ODMR) of the NV centers, as well as the surface conductivity, as a function of the nitrogen implantation fluence. The disappearance of the conductivity with increasing nitrogen implantation fluence coincides with the appearance of photoluminescence and ODMR signals from negatively charged NV centers. This finding indicates that band bending is not exclusively determined by the work-function difference between diamond and the surface acceptor material, but by the finite density of surface acceptors. This work emphasizes the importance of distinguishing work-function-difference-limited band bending and surface-acceptor-density-limited band bending when modeling the surface transfer doping, and provides useful insights for the development of devices based on hydrogen-terminated diamond.