Low-energy Electron Reflectivity from Graphene

TL;DR

This study investigates how low-energy electrons reflect from graphene layers, revealing a series of minima that depend on the number of layers and substrate interactions, combining theoretical and experimental approaches.

Contribution

It demonstrates that the number of reflectivity minima correlates with the number of graphene layers using first-principles calculations and experimental validation.

Findings

Number of minima equals number of layers minus one for free-standing graphene.

Experimental results confirm the theoretical prediction for supported graphene.

Additional minima can occur depending on substrate interactions.

Abstract

Low-energy reflectivity of electrons from single- and multi-layer graphene is examined both theoretically and experimentally. A series of minima in the reflectivity over the energy range of 0 - 8 eV are found, with the number of minima depending on the number of graphene layers. Using first-principles computations, it is demonstrated that a free standing n-layer graphene slab produces n-1 reflectivity minima. This same result is also found experimentally for graphene supported on SiO2. For graphene bonded onto other substrates it is argued that a similar series of reflectivity minima is expected, although in certain cases an additional minimum occurs, at an energy that depends on the graphene-substrate separation and the effective potential in that space.