Abstract
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). 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. 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. By varying the carbon deposition temperature between 800 –1100 °C, 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. 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. Bilayer and multilayer graphene were directly identified from areas that exhibited Raman characteristics of turbostratic graphene using high-resolution TEM imaging. Raman maps of the pertinent modes reveal large regions of turbostratic graphene on Ni(111) thin films at a deposition temperature of 1100 °C.
Highlights
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
Using physical vapor deposition (PVD), large-area turbostratic graphene was grown on heteroepitaxial Ni(111) thin films in a continual process with precise control of the deposition temperature, beam flux, and total amount of carbon deposited
Low ID/IG ratios observed from as-grown samples deposited at 1000 °C and 1100 °C represent the high-quality nature of the graphene grown via PVD
Summary
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. Relative rotations between graphene layers could provide a novel route to overcome the restrictions interfacial interactions impose on the desirable electronic properties of SLG. Localized areas of twisted bilayer and few-layer graphene have been investigated using characteristic Raman signatures after growth through CVD on Cu or by manipulating mechanically exfoliated graphene sheets[30,31,32,33,34,35,36,37]. While these findings are motivating, the properties of as-grown turbostratic graphene and its possible application remain largely unexplored. We systematically investigate the prevalence of as-grown turbostratic graphene with combination Raman modes within the region 1650–2300 cm−1 30,31, various features of the 2D peak[25,40] and electron microscopy
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