Incommensurability and negative thermal expansion of single layer hexagonal boron nitride

Kriegel, Marko A.; Omambac, Karim M.; Franzka, Steffen; Heringdorf, Frank-J. Meyer zu; Hoegen, M. Horn‐von

doi:10.1016/j.apsusc.2023.157156

Cited by 5 publications

(4 citation statements)

References 45 publications

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“…The pattern exhibits 3-fold symmetry reflecting the underlying symmetry of the Ir(111) substrate and the 3-fold symmetry of the h BN layer . It is well-known that many 2D systems form moiré networks as result of the different lattice spacing and possible rotation of the 2D layer and substrate. ,− For h BN on Ir(111) such moiré pattern has been observed in diffraction ,,− and STM. , In the SPA-LEED images of Figure the unambiguous identifier of such h BN related moiré pattern is a hexagonal network of satellite spots surrounding the (00) spot and all integer order diffraction spots.…”

Section: Results By Spa-leedmentioning

confidence: 88%

Interplay of Kinetic Limitations and Disintegration: Selective Growth of Hexagonal Boron Nitride and Borophene Monolayers on Metal Substrates

Omambac,

Kriegel,

Petrović

et al. 2023

ACS Nano

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The CVD growth of bielemental 2D-materials by using molecular precursors involves complex formation kinetics taking place at the surface and sometimes also subsurface regions of the substrate. Competing microscopic processes fundamentally limit the parameter space for optimal growth of the desired material. Kinetic limitations for diffusion and nucleation cause a high density of small domains and grain boundaries. These are usually overcome by increasing the growth temperature and decreasing the growth rate. In contrast, the nature of molecular precursors with limited thermal stability can result in dissociation and preferential desorption, leading to an undesired or ill-defined composition of the 2D-material.Here we demonstrate these constraints in a combined lowenergy electron diffraction and low-energy electron microscopy study by examining the selective formation of single-layer hexagonal boron nitride (hBN) and borophene on Ir(111) using a borazine precursor. We derive a temperature−pressure phase diagram and apply classical nucleation theory to describe our results. By considering the competing processes, we find an optimum growth temperature for hBN of 950 °C. At lower temperatures, the hBN island density is increased, while at higher temperatures the precursor disintegrates and borophene is formed. Our results introduce an additional aspect that must be considered in any high-temperature growth of bielemental 2D-materials from single molecular precursors.

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Section: Results By Spa-leedmentioning

confidence: 88%

Interplay of Kinetic Limitations and Disintegration: Selective Growth of Hexagonal Boron Nitride and Borophene Monolayers on Metal Substrates

Omambac,

Kriegel,

Petrović

et al. 2023

ACS Nano

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“…Both graphene and graphane have negative thermal expansion properties over an extended temperature range, specifically, at temperatures below about 1150 K. However, graphane is thermally contracted more significantly than graphene. Contraction with increasing temperature or negative thermal expansion is a potentially useful and unusual property for a crystalline material, , and very few solid materials possess strongly negative expansions over a broad temperature range. , For both graphene and graphane, the coefficient of thermal expansion increases as their temperature is increased. However, differences do exist, as the two materials have different thermal expansion coefficients.…”

Section: Resultsmentioning

confidence: 99%

Molecular Dynamics Modeling of Thermal Contraction, Heat Capacity, and Thermal Rippling of Graphane and Fluorographene for Thermal Applications

Chen,

Qin

2024

ACS Appl. Nano Mater.

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In spite of significant efforts to investigate the ability of hydrogenated and fluorinated graphene to conduct heat, little research has focused particularly on their other thermal properties, such as thermal contraction, heat capacity, and thermal rippling, which have implications for the development of thermal nanotechnology. In an attempt to determine these thermal properties, a few experiments have been carried out, with rather conflicting results. In the present study, calculations were performed using molecular dynamics to investigate the thermal properties of graphane and fluorographene and especially the phenomena involved. The thermal expansion coefficients, heat capacities, thermal fluctuations, and bending rigidities were determined at different temperatures. The results indicated that graphane is thermally contracted more significantly than graphene. The calculated molar heat capacity at constant volume is about 25.00 J/(mol·K) for graphene and about 29.26 J/(mol·K) for graphane. The specific heat capacity of fluorographene is always lower than that of graphane. While thermally excited ripples spontaneously appear in graphene, fully hydrogenated or fluorinated graphene is substantially unrippled due to its very high bending rigidities. However, partially hydrogenated or fluorinated graphene exhibits strong thermal fluctuations. Furthermore, significant out-of-plane fluctuations may occur in partially fluorinated graphene. Thermal fluctuations of graphene are more sensitive to temperature than those of graphane and fluorographene.

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“…SEM images show that the surface morphology of most samples is coarse and the edges of the grains are curled. This may be attributable to the negative thermal expansion coefficient of h-BN, 42 which leads to the grains expanding laterally during the cooling process after growth, causing the edges of the grains to curl. 43 When the m -miscut angle of the sapphire substrate is 0.1°, some nanoscale grains coalesce to form smooth micron-scale grains, as shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

Influence of sapphire substrate with miscut angles on hexagonal boron nitride films grown by halide vapor phase epitaxy

et al. 2023

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Incommensurability and negative thermal expansion of single layer hexagonal boron nitride

Cited by 5 publications

References 45 publications

Interplay of Kinetic Limitations and Disintegration: Selective Growth of Hexagonal Boron Nitride and Borophene Monolayers on Metal Substrates

Interplay of Kinetic Limitations and Disintegration: Selective Growth of Hexagonal Boron Nitride and Borophene Monolayers on Metal Substrates

Molecular Dynamics Modeling of Thermal Contraction, Heat Capacity, and Thermal Rippling of Graphane and Fluorographene for Thermal Applications

Influence of sapphire substrate with miscut angles on hexagonal boron nitride films grown by halide vapor phase epitaxy

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