Tuning the Electronic and Optical Properties of Impurity-Engineered Two-Dimensional Graphullerene Half-Semiconductors

TL;DR

This study uses spin-dependent density functional theory to analyze how impurity doping in monolayer graphullerene can tune its electronic, magnetic, and optical properties for potential spintronic applications.

Contribution

It provides the first comprehensive theoretical analysis of impurity effects on the electronic and optical properties of monolayer graphullerene.

Findings

Pristine graphullerene is a direct band gap semiconductor with ~1.5 eV gap.

Impurities induce spin-dependent deep levels and magnetic moments.

Impurity engineering tunes the band gap from 0.43 eV to 1.5 eV, covering NIR and SWIR regimes.

Abstract

A novel material consisting of a monolayer of C$_{60}$ buckyballs with hexagonal symmetry has recently been observed experimentally, named graphullerene. In this study, we present a comprehensive \textit{ab-initio} theoretical analysis of the electronic and optical properties of both pristine and impurity-engineered monolayer graphullerene using spin-dependent density functional theory (spin-DFT). Our findings reveal that graphullerene is a direct band gap semiconductor with a band gap of approximately 1.5 eV at the $\Gamma$ point, agreeing well with experimental data. Notably, we demonstrate that by adding impurities, in particular substitutional nitrogen, substitutional boron, or adsorbent hydrogen, to graphullerene results in the formation of spin-dependent deep donor and deep acceptor levels, thereby giving rise to a variety of half-semiconductors. All the impurities exhibit a magnetic moment of approximately $\mu_B$ per impurity. This impurity engineering enables the tuning of spin-polarized exciton properties in graphullerene, with spin-dependent band gap energies ranging from 0.43 eV ($\lambda \sim$ 2.9 $\mu$m) to 1.5 eV ($\lambda \sim$ 820 nm), covering the near-infrared (NIR) and short-wavelength infrared (SWIR) regimes. Our results suggest that both pristine and impurity-engineered graphullerene have significant potential for the development of carbon-based 2D semiconductor spintronic and opto-spintronic devices.