For example, recent graphene studies have focused on the impact of interfacial interactions on charge transportation 17 and spin injection efficiency 21. As a true two-dimensional system, graphene provides an intriguing opportunity to study the fundamental surface physics and interfacial interactions and, in turn, their property/function relations. SLG is a two-dimensional network of sp 2 bonded carbon atoms that exhibits near-ballistic transport of electrons 17, among other remarkable properties 18, enabling a broad range of applications from graphene field effect transistors 19 for carbon-based electronics to molecular sieves 20 for water treatment. Despite these notable advances, out-of-plane π-orbital hybridization between SLG and its substrate 15 can limit its theoretical capacity due to charge scattering 16. Widely considered a prominent growth technique, CVD has produced graphene on the meter scale 13 and through precise constraint of growth parameters, has demonstrated control over the morphology 14. To date, graphene has been fabricated from a range of carbon sources through a variety of top-down and bottom-up approaches including, mechanical and chemical exfoliation of graphite 5, CVD 6, 7, molecular beam epitaxy 8, 9, graphitization of SiC 10, longitudinal unzipping of carbon nanotubes 11 and, growth from solid carbon sources, such as polymers 12. It was not until Novoselov and Giem established micromechanical cleavage of bulk graphite as a repeatable method to isolate single-layer graphene (SLG) 3 that graphene began to receive tremendous interest from academia and industry 4. Graphene synthesis originated in the 1960s with graphitization of SiC 1 as well as through chemical vapor deposition (CVD) on Pt(111) 2. Raman maps of the pertinent modes reveal large regions of turbostratic graphene on Ni(111) thin films at a deposition temperature of 1100 ☌. Bilayer and multilayer graphene were directly identified from areas that exhibited Raman characteristics of turbostratic graphene using high-resolution TEM imaging. Combination Raman modes of as-grown graphene within the frequency range of 1650 cm −1 to 2300 cm −1, along with features of the Raman 2D mode, were employed as signatures of turbostratic graphene.
By varying the carbon deposition temperature between 800 –1100 ☌, we report an increase in the graphene quality concomitant with a transition in the size of uniform thickness graphene, ranging from nanocrystallites to thousands of square microns.
While the growth of AB Bernal graphene through chemical vapor deposition has been widely reported, we investigate the growth of turbostratic graphene on heteroepitaxial Ni(111) thin films utilizing physical vapor deposition. Multilayer graphene with relative rotations between carbon layers, known as turbostratic graphene, can effectively decouple the electronic states of adjacent layers, preserving properties similar to that of SLG. Single-layer graphene has demonstrated remarkable electronic properties that are strongly influenced by interfacial bonding and break down for the lowest energy configuration of stacked graphene layers (AB Bernal).