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Growth kinetics of white graphene (h-BN) on a planarised Ni foil surface.

Cho H, Park S, Won DI, Kang SO, Pyo SS, Kim DI, Kim SM, Kim HC, Kim MJ - Sci Rep (2015)

Bottom Line: The morphology of the surface and the grain orientation of metal catalysts have been considered to be two important factors for the growth of white graphene (h-BN) by chemical vapour deposition (CVD).Atmospheric annealing with hydrogen reduced the nucleation sites of h-BN, which induced a large crystal size mainly grown from the grain boundary with few other nucleation sites in the Ni foil.A higher growth rate was observed from the Ni grains that had the {110} or {100} orientation due to their higher surface energy.

View Article: PubMed Central - PubMed

Affiliation: 1] Soft Innovative Materials Research Center, Korea Institute of Science and Technology, Chudong-ro 92, Bongdong-eup, Wanju-gun, Jeollabuk-do 565-905, Republic of Korea [2] Department of Organic Materials and Fiber Engineering, Chonbuk National University, 567, Baekje-daero, Deokjin-gu, Jeonju-si, Jeollabuk-do 561-756, Republic of Korea.

ABSTRACT
The morphology of the surface and the grain orientation of metal catalysts have been considered to be two important factors for the growth of white graphene (h-BN) by chemical vapour deposition (CVD). We report a correlation between the growth rate of h-BN and the orientation of the nickel grains. The surface of the nickel (Ni) foil was first polished by electrochemical polishing (ECP) and subsequently annealed in hydrogen at atmospheric pressure to suppress the effect of the surface morphology. Atmospheric annealing with hydrogen reduced the nucleation sites of h-BN, which induced a large crystal size mainly grown from the grain boundary with few other nucleation sites in the Ni foil. A higher growth rate was observed from the Ni grains that had the {110} or {100} orientation due to their higher surface energy.

No MeSH data available.


The comparison AFM images of (a) the raw Ni foil, (b) the Ni foil with LPH2, (c) the Ni foil with ECP/LPH2 and (d) the Ni foil with ECP/APH2.
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f1: The comparison AFM images of (a) the raw Ni foil, (b) the Ni foil with LPH2, (c) the Ni foil with ECP/LPH2 and (d) the Ni foil with ECP/APH2.

Mentions: H2 annealing of the Ni foil is a generic procedure performed right before the growth procedure, as H2 annealing can provide large grains and clean surfaces for uniform h-BN growth. A variety of particles (Ni, SiO2, Al2O3, Cr, Co, Mn, and MgO), however, were formed on the surface after low pressure (LP) H2 annealing (200 mTorr), as the Ni foils have metal impurities and residual of Si lubricant coatings on the surface from the rolling process. The chemical elements of the particles were analysed by energy-dispersive X-ray spectroscopy (EDS) in a scanning electron microscope (SEM) and are presented in Supplementary Fig. S2. From the viewpoint of growth mechanism, various particles and poor surface condition of catalyst can easily act as nucleation sites for the growth. Thus, in order to remove the particles, including residual of Si lubricants, and to planarise the surface that has edges, steps and uneven surface, ECP process was attempted, and then LP H2 annealing was followed. As shown in Fig. 1(c) and Fig. 2(b), the number of particles and the surface roughness substantially decreased. The root mean square (RMS) was evaluated by using the atomic force microscopy (AFM) (Fig. 1). Among all conditions, the complete removal of particles and lowest surface roughness of Ni foil were acquired by ECP/APH2 as shown in the SEM images (Fig. 2(a,b)). The RMS value of the condition was 1.037 nm with a small deviation. In our results, the ECP/AP process provided the platform to clean and planarise the Ni foil on the nanometre scale. Detailed discussion about the hydrogen annealing under atmospheric pressure (APH2) will be addressed in the next section and we provided new abbreviations about the detailed experimental conditions in supplementary information.


Growth kinetics of white graphene (h-BN) on a planarised Ni foil surface.

Cho H, Park S, Won DI, Kang SO, Pyo SS, Kim DI, Kim SM, Kim HC, Kim MJ - Sci Rep (2015)

The comparison AFM images of (a) the raw Ni foil, (b) the Ni foil with LPH2, (c) the Ni foil with ECP/LPH2 and (d) the Ni foil with ECP/APH2.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4496663&req=5

f1: The comparison AFM images of (a) the raw Ni foil, (b) the Ni foil with LPH2, (c) the Ni foil with ECP/LPH2 and (d) the Ni foil with ECP/APH2.
Mentions: H2 annealing of the Ni foil is a generic procedure performed right before the growth procedure, as H2 annealing can provide large grains and clean surfaces for uniform h-BN growth. A variety of particles (Ni, SiO2, Al2O3, Cr, Co, Mn, and MgO), however, were formed on the surface after low pressure (LP) H2 annealing (200 mTorr), as the Ni foils have metal impurities and residual of Si lubricant coatings on the surface from the rolling process. The chemical elements of the particles were analysed by energy-dispersive X-ray spectroscopy (EDS) in a scanning electron microscope (SEM) and are presented in Supplementary Fig. S2. From the viewpoint of growth mechanism, various particles and poor surface condition of catalyst can easily act as nucleation sites for the growth. Thus, in order to remove the particles, including residual of Si lubricants, and to planarise the surface that has edges, steps and uneven surface, ECP process was attempted, and then LP H2 annealing was followed. As shown in Fig. 1(c) and Fig. 2(b), the number of particles and the surface roughness substantially decreased. The root mean square (RMS) was evaluated by using the atomic force microscopy (AFM) (Fig. 1). Among all conditions, the complete removal of particles and lowest surface roughness of Ni foil were acquired by ECP/APH2 as shown in the SEM images (Fig. 2(a,b)). The RMS value of the condition was 1.037 nm with a small deviation. In our results, the ECP/AP process provided the platform to clean and planarise the Ni foil on the nanometre scale. Detailed discussion about the hydrogen annealing under atmospheric pressure (APH2) will be addressed in the next section and we provided new abbreviations about the detailed experimental conditions in supplementary information.

Bottom Line: The morphology of the surface and the grain orientation of metal catalysts have been considered to be two important factors for the growth of white graphene (h-BN) by chemical vapour deposition (CVD).Atmospheric annealing with hydrogen reduced the nucleation sites of h-BN, which induced a large crystal size mainly grown from the grain boundary with few other nucleation sites in the Ni foil.A higher growth rate was observed from the Ni grains that had the {110} or {100} orientation due to their higher surface energy.

View Article: PubMed Central - PubMed

Affiliation: 1] Soft Innovative Materials Research Center, Korea Institute of Science and Technology, Chudong-ro 92, Bongdong-eup, Wanju-gun, Jeollabuk-do 565-905, Republic of Korea [2] Department of Organic Materials and Fiber Engineering, Chonbuk National University, 567, Baekje-daero, Deokjin-gu, Jeonju-si, Jeollabuk-do 561-756, Republic of Korea.

ABSTRACT
The morphology of the surface and the grain orientation of metal catalysts have been considered to be two important factors for the growth of white graphene (h-BN) by chemical vapour deposition (CVD). We report a correlation between the growth rate of h-BN and the orientation of the nickel grains. The surface of the nickel (Ni) foil was first polished by electrochemical polishing (ECP) and subsequently annealed in hydrogen at atmospheric pressure to suppress the effect of the surface morphology. Atmospheric annealing with hydrogen reduced the nucleation sites of h-BN, which induced a large crystal size mainly grown from the grain boundary with few other nucleation sites in the Ni foil. A higher growth rate was observed from the Ni grains that had the {110} or {100} orientation due to their higher surface energy.

No MeSH data available.