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We report the results of a comparative investigation of graphene films prepared on Si(100) and fused silica (SiO2) combining pulsed laser deposition and rapid thermal annealing using Ni catalyst. The effect of modifying the substrate and/or growth temperature (600–1,000°C) of graphene synthesis was investigated by Raman microspectroscopy mapping. Graphene grown on Si(100) was multilayered, and various nickel silicide phases had formed underneath, revealing dependence on the growth temperature. Films prepared on SiO2 mainly comprised bilayered and trilayered graphene, with no traces of nickel silicide. Analysis of Raman D, G, and 2D peak intensities and positions showed that modifying the growth temperature had different effects when a Si(100) or a SiO2 substrate is used. These findings advance our understanding of how different combinations of substrate and thermal processing parameters affect graphene synthesis from solid carbon source using nickel as a catalyst. This knowledge will enable better control of the properties of graphene film (defects, number of layers, etc.) and will have a high potential impact on the design of graphene‐based devices for scientific or industrial applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Transfer-free Graphene with dominant bilayer is synthetized from pulsed laser deposition. • Thermal annealing with Ni catalyst converts the amorphous carbon precursor into graphene. • The Ni catalyst undergoes a three-step mechanism of dewetting during thermal annealing. • Graphene synthesis is compatible with the nickel dewetting during thermal annealing. • The residual Ni particles are removed by a final acidic treatment, revealing the graphene films. We report the transformation of amorphous carbon deposited by pulsed laser deposition (PLD) into free transfer graphene, associated with dewetting of the nickel catalyst film during rapid thermal annealing. Prior to graphene synthesis, dewetting of the pure nickel film is investigated versus thickness and temperature. Then a parametric study of graphene synthesis from an amorphous carbon film 2 nm thick is carried out by varying the starting thickness of the nickel catalyst (25, 50, 150 nm) at a temperature of 900 °C. The graphene layers form on the top surface of the nickel film and at the interface between the nickel film and the SiO 2 substrate, due to rapid diffusion of C through the Ni film. The concomitant nickel dewetting process enables exposure of the interfacial graphene while some graphene layers agglomerate on nickel particles. By removing the nickel particles with an acid treatment, interfacial graphene (also called free transfer graphene) was formed directly on the SiO 2 substrate, avoiding a time consuming and relatively complicated transfer process. This work paves the way for the control of the number of layers of free transfer graphene using a solid carbon source and a nickel film catalyst. [ABSTRACT FROM AUTHOR]

Here we report the low-defect synthesis of bilayer graphene film on SiO 2 with a nickel catalyst using pulsed laser deposition combined with rapid thermal annealing. A parametric study was performed with various initial amorphous carbon (a-C) film thicknesses and annealing temperatures and a fixed nickel catalyst film thickness. Raman spectra and mapping over large areas of up to 100 × 100 μm2 were used to investigate the structure and the defects of graphene films. Optimal conditions for graphene growth were an initial a-C film thickness of 2 nm and an annealing temperature of 900 °C. Results showed that 76% of the optimized film contained graphene bilayers, and 18% of the optimized film contained graphene monolayers. A transmittance of 87% at 550 nm is observed without any transfer process from the SiO 2 substrate. This paper presents experimental guidelines for optimal synthesis conditions to control graphene growth by pulsed laser deposition. • Low defect graphene is obtained from carbon film deposited by pulse laser ablation. • Optimal synthesis conditions require a 2 nm a-C film annealed at 900 °C in vacuum. • Bilayer graphene is detected on 76% of a typical 100 × 100 μm2 RAMAN probed surface. • The transmittance of the bilayer graphene on SiO 2 without transfer is 87% at 550 nm. [ABSTRACT FROM AUTHOR]