Determining crystal phase purity in c-BP through X-ray absorption spectroscopy.

Area of Science:

• Materials Science
• Solid-State Physics
• Spectroscopy

Background:

• Cubic boron phosphide (c-BP) is a semiconductor with potential applications.
• Understanding the precise structure of c-BP is crucial for optimizing its properties.
• X-ray absorption near-edge spectroscopy (XANES) is a powerful tool for probing local atomic and electronic structures.

Purpose of the Study:

• To elucidate the structural properties of cubic boron phosphide (c-BP) samples.
• To identify the origins of spectral features in the boron K-edge XANES spectra.
• To investigate the potential presence of amorphous boron in synthesized c-BP.

Main Methods:

• X-ray absorption near-edge spectroscopy (XANES) at the boron K-edge and phosphorus L2,3-edge.
• First-principles density functional theory (DFT) calculations using the excited electron core-hole (XCH) approach.
• Modeling of XANES spectra for perfect c-BP, intrinsic point defects, hexagonal BP, and amorphous boron structures.

Main Results:

• The phosphorus L2,3-edge spectrum was well-reproduced by a perfect c-BP model.
• The boron K-edge spectrum showed a broad, gradual onset not explained by perfect c-BP, defects, or hexagonal BP.
• Calculated formation enthalpies suggested co-growth of amorphous boron phases.
• XANES spectra of amorphous boron structures matched the experimental broad onset observed in c-BP samples.

Conclusions:

• The experimental boron K-edge XANES spectra of c-BP samples provide evidence for the presence of amorphous boron clusters.
• Amorphous boron co-existing with crystalline c-BP can significantly influence the material's overall structural and electronic properties.
• This finding highlights the importance of controlling amorphous phase formation during c-BP synthesis for targeted applications.