# How carbon vacancies can affect the properties of group IV color centers in diamond: A study of thermodynamics and kinetics

## TL;DR

This paper uses density-functional theory to study how carbon vacancies affect the properties of Group IV color centers in diamond, focusing on their formation, impact on spin coherence, and ways to mitigate these effects for quantum applications.

## Contribution

It provides a detailed thermodynamic and kinetic analysis of vacancy-center complexes and suggests experimental strategies to improve color center stability and coherence.

## Key findings

- V$_C$-X$V$ complexes can form readily, affecting color center properties.
- Chemical doping and external bias can reduce complex formation.
- Presence of vacancies can decrease spin coherence times.

## Abstract

Recently there has been much interest in using Group IV elements from the Periodic Table to fabricate and study X$V$ color centers in diamond where X = Si, Ge, Sn, or Pb and $V$ is a carbon vacancy. These Group IV color centers have a number of interesting spin and optical properties which could potentially make them better candidates than N$V^-$ centers for important applications in quantum computing and quantum information processing. Unfortunately, the very same ion implantation process that is required to create these X$V$ color centers in diamond necessarily also produces many carbon vacancies ($V_{\rm C}$) which can form complexes with these color centers ($V_{\rm C}-$X$V$) that can dramatically affect the properties of the isolated X$V$ color centers. The main focus of this work is to use density-functional theory (DFT) to study the thermodynamics and kinetics of the formation of these $V_{\rm C}-$X$V$ complexes and to suggest experimental ways to impede this process such as varying the Fermi level of the host diamond material through chemical doping or applying an external electrical bias. We also include a discussion of how the simple presence of many $V_{\rm C}$ can negatively impact the spin coherence times ($T_2$) of Group IV color centers through the presence of acoustic phonons.