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Superhard boron-carbon materials are of prime interest due to their non-oxidizing properties at high temperatures compared to diamond-based materials and their non-reactivity with ferrous metals under extreme conditions. In this work, evolutionary algorithms combined with density functional theory have been utilized to predict stable structures and properties for the boron-carbon system, including the elusive superhard BC5 compound. We report on the microwave plasma chemical vapor deposition on a silicon substrate of a series of composite materials containing amorphous boron-doped graphitic carbon, boron-doped diamond, and a cubic hard-phase with a boron-content as high as 7.7 at%. The nanoindentation hardness of these composite materials can be tailored from 8 GPa to as high as 62 GPa depending on the growth conditions. These materials have been characterized by electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, X-ray diffraction, and nanoindentation hardness, and the experimental results are compared with theoretical predictions. Our studies show that a significant amount of boron up to 7.7 at% can be accommodated in the cubic phase of diamond and its phonon modes and mechanical properties can be accurately modeled by theory. This cubic hard-phase can be incorporated into amorphous boron-carbon matrices to yield superhard materials with tunable hardness values.
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Synthesis and Properties of Plasmonic Boron‐Hyperdoped Silicon Nanoparticles
Abstract Electronic properties of silicon, the most important semiconductor material, are controlled through doping. The range of achievable properties can be extended by hyperdoping, i.e., doping to concentrations beyond the nominal equilibrium solubility of the dopant. Here, hyperdoping is achieved in a laser pyrolysis reactor capable of providing nonequilibrium conditions, where doping is governed by kinetics rather than thermodynamics. High resolution scanning transmission electron microscopy (TEM) with energy‐dispersive X‐ray spectroscopy shows that the boron atom distribution in the hyperdoped nanoparticles is relatively uniform. The hyperdoped nanoparticles demonstrate tunable localized surface plasmon resonance (LSPR) and are stable in air for periods of at least one year. The hyperdoped nanoparticles are also stable upon annealing at temperatures up to 600 °C. Furthermore, boron hyperdoping does not change the diamond cubic crystal structure of silicon, as demonstrated in detail by high flux synchrotron X‐ray diffraction and pair distribution function (PDF) analysis, supported by high‐resolution TEM analysis.
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- Award ID(s):
- 1809439
- PAR ID:
- 10435595
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Functional Materials
- Volume:
- 29
- Issue:
- 8
- ISSN:
- 1616-301X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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