Abstract
Density functional theory predictions have been combined with the microwave-plasma chemical vapor deposition technique to explore metastable synthesis of boron-rich boron-carbide materials. A thin film synthesis of high-hardness (up to 37 GPa) B50C2 via chemical vapor deposition was achieved. Characterization of the experimental crystal structure matches well with a new theoretical model structure, with carbon atoms inserted into the boron icosahedra and 2b sites in a α-tetragonal B52 base structure. Previously reported metallic B50C2 structures with carbons inserted only into the 2b or 4c sites are found to be dynamically unstable. The newly predicted structure is insulating and dynamically stable, with a computed hardness value and electrical properties in excellent agreement with the experiment. The present study thus validates the density functional theory calculations of stable crystal structures in boron-rich boron-carbide system and provides a pathway for large-area synthesis of novel materials by the chemical vapor deposition method.
Highlights
Boron-rich boron-carbide materials are of interest because of their thermal stability, high mechanical strength and their ability to function in extreme conditions of pressure, temperature, and corrosive environments
The elemental analysis was confirmed by X-ray photoelectron spectroscopy (XPS) and the phase determination was made using X-ray diffraction (XRD) analysis
A Rietveld refinement was performed for B50C2 phase along with our newly-proposed insulating B50C2 phase
Summary
Boron-rich boron-carbide materials are of interest because of their thermal stability, high mechanical strength and their ability to function in extreme conditions of pressure, temperature, and corrosive environments. Boron-rich boron-carbide materials synthesis by chemical vapor deposition methods continues to be relatively unexplored and a challenging endeavor. Most of the novel high boron compounds are formed in high pressure high temperature (HPHT) cells, which produce very small volumes of material for analysis. Boron-rich boron-carbide in varying stoichiometric ratios has been made by HPHT methods[12], but these methods are not scalable for producing large area coatings and can be difficult in controlling the impurities. Microwave-plasma chemical vapor deposition (CVD) methods are better for controlling impurities in the material and can be used for large-area synthesis. We report the growth of high-hardness B50C2 thin films via CVD and experimentally characterize their properties by comparing to the predicted behaviors of a new theoretical stable and insulating B50C2 structure by first-principles calculations
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call