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. 2015 Mar 11:6:6499.
doi: 10.1038/ncomms7499.

Silane-catalysed fast growth of large single-crystalline graphene on hexagonal boron nitride

Shujie Tang  1 , Haomin Wang  2 , Hui Shan Wang  3 , Qiujuan Sun  3 , Xiuyun Zhang  4 , Chunxiao Cong  5 , Hong Xie  2 , Xiaoyu Liu  2 , Xiaohao Zhou  6 , Fuqiang Huang  7 , Xiaoshuang Chen  6 , Ting Yu  5 , Feng Ding  4 , Xiaoming Xie  8 , Mianheng Jiang  8
Affiliations

Silane-catalysed fast growth of large single-crystalline graphene on hexagonal boron nitride

Shujie Tang et al. Nat Commun. .

Abstract

The direct growth of high-quality, large single-crystalline domains of graphene on a dielectric substrate is of vital importance for applications in electronics and optoelectronics. Traditionally, graphene domains grown on dielectrics are typically only ~1 μm with a growth rate of ~1 nm min(-1) or less, the main reason is the lack of a catalyst. Here we show that silane, serving as a gaseous catalyst, is able to boost the graphene growth rate to ~1 μm min(-1), thereby promoting graphene domains up to 20 μm in size to be synthesized via chemical vapour deposition (CVD) on hexagonal boron nitride (h-BN). Hall measurements show that the mobility of the sample reaches 20,000 cm(2) V(-1) s(-1) at room temperature, which is among the best for CVD-grown graphene. Combining the advantages of both catalytic CVD and the ultra-flat dielectric substrate, gaseous catalyst-assisted CVD paves the way for synthesizing high-quality graphene for device applications while avoiding the transfer process.

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Figures

Figure 1
Figure 1. The gaseous catalyst-assisted CVD of graphene on h-BN.
(a) The growth duration dependence of the domain dimensions for single-crystalline graphene in the presence of silane (black) or germane (red) gaseous catalysts and no catalyst (green). The diameter of the graphene domain is measured as the diagonal length of the hexagonal graphene crystal, and the growth temperature is 1,280 °C. (b) The graphene growth rates plotted as a function of the dimensions of the single-crystalline domains obtained in this work and those reported in the literature. The data points are labelled with the reference number from whence they came in brackets. (c) Schematic of the gaseous catalyst-assisted chemical vapour deposition process, visualizing the carbon (black), nitrogen (blue), boron (yellow), silicon (red) and hydrogen (small grey) atoms as spheres in the illustration. The schematic illustrates simplified schemes of the catalytic growth of monolayer graphene onto h-BN, where silicon atoms from the decomposition of SiH4 attach to the edge of the graphene and assist its growth.
Figure 2
Figure 2. Density functional calculation of the reaction between a C2H2 molecule with the commonly observed armchair graphene edge.
(a) without and (b) with an Si atom as a catalyst on the graphene edge. The black, white and yellow balls represent carbon, hydrogen and silicon atoms, respectively.
Figure 3
Figure 3. The investigation on crystallinity and alignment of graphene domains grown on h-BN.
(a) Topography image of a typical single-crystalline graphene domain with a diameter of 20 μm. The dashed line frames the shape of the graphene grain. The line scan shows the graphene thickness to be 0.37 nm. The scale bar is 10 μm. (b) The AFM friction image of the selected area in a, where the giant moiré pattern with a periodicity of 13.9 nm can be clearly seen. The scale bar is 100 nm. Atomic-resolution AFM images of (c) graphene and (d) h-BN taken from the areas marked by the blue and red dots in a, respectively. During the measurement, the scanning angles are always kept the same. The scale bars are 1 nm. (e) Pie charts of the distribution of the type of graphene domains obtained with/without gaseous catalysts. Type ‘A’ indicates a graphene domain that is precisely aligned with the underlying h-BN, type ‘B’ is one whose lattice is rotated 30° with respect to the underlying h-BN lattice, and type ‘C’ is one with a polycrystalline structure.
Figure 4
Figure 4. Raman analyses on graphene domains grown on h-BN.
(a) Topography images of two graphene domains grown on an h-BN surface. The white line across the image indicates a wrinkle on the h-BN surface formed during cooling. The scale bar is 2 μm. (b) Magnified view from the red box in a, where the presence of a giant moiré pattern indicates precisely aligned graphene with respect to the h-BN. (c) Magnified view from the blue box in a, where no detectable moiré pattern is seen. The scale bars in b and c are 100 nm. (d) Raman spectra taken from Domain 1 (lower plot) and Domain 2 (upper plot) in a. The full-width at half-maximum for each peak is given in parentheses with the peak location value, and the wavelength of the exciting laser is 488 nm.
Figure 5
Figure 5. Transport measurement of the single-crystalline graphene precisely aligned with the underlying h-BN.
(a) Back-gate voltage (Vg) dependence of the longitudinal resistance at different temperatures. Inset shows the temperature dependence of the resistance at the Dirac point (DP; red spheres) and satellite peaks at the hole doping Secondary Dirac point (SDP) (black spheres). (b) Longitudinal (Rxx, blue) and Hall resistance (Rxy, red) versus Vg at temperature T=300 K and magnetic field B=9 T. (c,d) Quantum Hall effect fan diagram of (c) Rxx and (d) Rxy as a function of Vg and B at a temperature of 2 K.
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