Research in 2D materials continues to advance at a rapid pace fueled by the discovery of novel electronic and optical properties and the isolation of new materials and advances in their growth. Since the original isolation of graphene, the range of materials that are available in a 2D form has grown to include semiconducting transition metal dichalcogenides, insulating boron nitride, ferromagnetic insulators, and superconductors. In many cases, the electronic, photonic, and mechanical properties of these 2D materials are fundamentally different than those of their bulk parent compounds. Therefore, these 2D materials hold tremendous promise for a range of novel applications that are not possible with bulk materials.
In order to fully harness the potential of 2D materials, there needs to be advances in the growth and characterization of them. Initial measurements on 2D materials took place using monolayers which were exfoliated from bulk crystals which typically limited the size of devices to the micron range. Recent advances have now enabled the wafer scale growth of many different 2D materials opening the way to industrial applications. There has also been progress on combining 2D and 3D growth for added functionality as seen in Fig. 1. Along with these improved materials comes the need for characterization tools that can probe the electronic and optical properties of 2D materials over a wide range of energy and spatial scales.
False colored scanning electron micrograph of layered indium selenide (InSe) pyramids and “streets” grown via powder vaporization on a silicon oxide substrate. Credit: Carlos Pernia, Brian Bersch, and Natalie Briggs (Penn State University).
False colored scanning electron micrograph of layered indium selenide (InSe) pyramids and “streets” grown via powder vaporization on a silicon oxide substrate. Credit: Carlos Pernia, Brian Bersch, and Natalie Briggs (Penn State University).
This special issue presents advances in the growth and characterization of these 2D materials. New methods for increasing the functionality of 2D materials are presented by creating heterostructures with multiple active layers, novel approaches to device fabrication, and chemical modification during growth. Several papers also demonstrate the growth and characterization of novel 2D materials and structures. Lastly, there are papers demonstrating new characterization methods to access the electronic structure of 2D materials.
