Doped 2D diamond: properties and applications

TL;DR

This study uses first-principles calculations to analyze doped 2D diamond nanosheets, revealing their stability, mechanical strength, and electronic properties, with potential applications in electronics and optoelectronics.

Contribution

It provides a detailed theoretical investigation of the structural, thermodynamic, elastic, and electronic properties of doped 2D diamond nanosheets with novel stacking configurations.

Findings

All four structures are stable according to phonon spectra and molecular dynamics.

C4N2 nanosheets have wide indirect band gaps suitable for substrate applications.

C4B2 nanosheets are semiconductors with direct band gaps of 1.6-2.0 eV, promising for optoelectronics.

Abstract

In the present paper, we investigate the structural, thermodynamic, dynamic, elastic, and electronic properties of doped 2D diamond C$_4$X$_2$ (X = B or N) nanosheets in both AA$'$A$''$ and ABC stacking configurations, by first-principles calculations. Those systems are composed of 3 diamond-like graphene sheets, with an undoped graphene layer between two 50% doped ones. Our results, based on the analysis of ab-initio molecular dynamics simulations, phonon dispersion spectra, and Born's criteria for mechanical stability, revealed that all four structures are stable. Additionally, their standard enthalpy of formation values are similar to the one of pristine 2D diamond, recently synthesized by compressing three graphene layers. The C$_4$X$_2$ (X = B or N) systems exhibit high elastic constant values and stiffness comparable to the diamond. The C$_4$N$_2$ nanosheets present wide indirect band gaps that could be advantageous for applications similar to the ones of the hexagonal boron nitride (h-BN), such as a substrate for high-mobility 2D devices. On the other hand, the C$_4$B$_2$ systems are semiconductors with direct band gaps, in the 1.6 - 2.0 eV range, and small effective masses, which are characteristics that may be favorable to high carrier mobility and optoelectronics applications.