New technique to reveal defect densities in graphene layers

Researchers from University of Central Florida (UCF) in collaboration with a researcher from Universidad Politécnica de Madrid (UPM) have published an article in Optica that suggests a new phenomenon when measuring the changes on the coherence of a light beam that strikes a monolayer of carbon atoms.

Researchers have shown that there is a direct relationship between light properties and structural properties of a two-dimensional material in a way that can determine the defect density of a layer. This paves the way toward a reliable quality control method when manufacturing graphene layers.

The capacity to control the interaction light-matter on a scale below the wavelength of the electromagnetic radiation used in an experiment has fascinating consequences for material sciences and a range of photonics technologies.

A team of researchers, including the Professor Félix Salazar from School of Mining and Energy Engineering (ETSIME) at UPM, has used a monolayer of graphene to show that the relative properties of the spatial coherence of light in the proximity of surfaces illuminated by randomized electromagnetic fields, is significantly affected by the density of defects in crystalline lattices of this material.

This direct relationship between the modifying properties of light and the number of defects of a layer after the analysis of the elastic interaction between photons and atoms allows researchers to detect the defects of two-dimensional materials such as graphene. The developed methodology can be used as a reliable method of production process control of two-dimensional layers.

In addition to the detection of defects in two-dimensional layers, the phenomenon can be used in reverse. That is, introducing defects in a controlled way would allow manufacturers to change the spatial properties of incident light, with applications in the technology of photonic devices and photovoltaic cells, among others.

Félix Salazar Bloise says, "We have found out a new phenomenon in an atom layer, essentially transparent, that is able to change the spatial coherence of the light through a two-dimensional material, and this can be used to find out the number of defects existing in a monolayer of atoms as well as to manipulate the incident light."

More information:
Roxana Rezvani Naraghi et al. Near-field coherence reveals defect densities in atomic monolayers, Optica (2017). DOI: 10.1364/OPTICA.4.000527

Provided by Universidad Politécnica de Madrid