Deuterium Adsorption on Free-Standing Graphene.

Mahmoud Mohamed Saad Abdelnabi,Chiara Izzo,Carlo Mariani,Maria Grazia Betti,Isabel García-Cortés,Kailong Hu,Giulia Di Bella,Alejandro Moroño,Antonio Polimeni,Elena Blundo,Marco Sbroscia,Isabel Rucandio,Gianluca Cavoto,Yoshikazu Ito

doi:10.3390/nano11010130

Abstract

A suitable way to modify the electronic properties of graphene—while maintaining the exceptional properties associated with its two-dimensional (2D) nature—is its functionalisation. In particular, the incorporation of hydrogen isotopes in graphene is expected to modify its electronic properties leading to an energy gap opening, thereby rendering graphene promising for a widespread of applications. Hence, deuterium (D) adsorption on free-standing graphene was obtained by high-energy electron ionisation of D and ion irradiation of a nanoporous graphene (NPG) sample. This method allows one to reach nearly 50 at.% D upload in graphene, higher than that obtained by other deposition methods so far, towards low-defect and free-standing D-graphane. That evidence was deduced by X-ray photoelectron spectroscopy of the C 1s core level, showing clear evidence of the D-C sp bond, and Raman spectroscopy, pointing to remarkably clean and low-defect production of graphane. Moreover, ultraviolet photoelectron spectroscopy showed the opening of an energy gap in the valence band. Therefore, high-energy electron ionisation and ion irradiation is an outstanding method for obtaining low defect D-NPG with a high D upload, which is very promising for the fabrication of semiconducting graphane on large scale.

Highlights

One of the most pursued key goals in graphene functionalisation is the achievement of a two-dimensional (2D) material with unvaried mechanical strength and stiffness but with different and tailored electronic and transport properties
nanoporous graphene (NPG) sample, we describe its direct exposure to a deuterium ion beam into a deuterium atmosphere, with the ions generated by the irradiation of the gas with 1.8 MeV electrons; the D+ ions are drifted with an applied electric field towards the graphene sample, to be deuterium loaded
We first describe the NPG preparation and cleaning procedures; we study by Raman and photoemission spectroscopy the D-adsorbed NPG achieved by bombardment with medium-energy ions

Summary

Introduction

One of the most pursued key goals in graphene functionalisation is the achievement of a two-dimensional (2D) material with unvaried mechanical strength and stiffness but with different and tailored electronic and transport properties. Graphane is the forecasted semiconducting [1,2,3] form of graphene, where the carbon (C) atoms in the honeycomb lattice are bonded to H atoms. Graphane and nano-structured/functionalised graphene may constitute innovative systems for designing highly efficient electronic devices, thanks to the remarkable mechanical robustness and flexibility typical of 2D materials [4,5,6], coupled with a semiconducting character [7,8,9,10], unlike graphene. Graphane as constituted by tritium (T)—the β-unstable isotope of hydrogen—covalently bonded to graphene, has been suggested to represent an ideal candidate for the realisation of a new detector able to measure the Nanomaterials 2021, 11, 130.

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Conclusion