Direct Synthesis of Ultrathin Hexagonal Boron Nitride Films on Si(001)

Area of Science:

• Materials Science
• Nanotechnology
• Solid State Physics

Background:

• Large-scale fabrication of hexagonal boron nitride (hBN) films is crucial for micro- and optoelectronic devices.
• Achieving well-oriented, high-quality hBN films on silicon substrates via chemical vapor deposition (CVD) remains a significant challenge.
• The formation of amorphous SiNx interlayers can hinder device performance.

Purpose of the Study:

• To develop a novel, scalable method for synthesizing ultrathin, well-oriented hBN films on Si(001) substrates.
• To explore spectroscopic ellipsometry as a rapid, non-destructive characterization technique for hBN films.
• To enable the fabrication of advanced hBN-based microelectronic and optoelectronic devices.

Main Methods:

• Continuous flow chemical vapor deposition (CVD) using borazine as a single-source precursor.
• Growth of hBN films on Si(001) substrates.
• Characterization using spectroscopic ellipsometry to determine film thickness, refractive index, and optical bandgap.

Main Results:

• Ultrathin, well-oriented hBN films with a thickness of 7 ± 1 layers were successfully synthesized.
• The grown hBN films exhibited near-perfect stoichiometry and a low surface roughness of 1.1 nm.
• Spectroscopic ellipsometry revealed a refractive index of 2.17 at 633 nm and an optical bandgap of 5.89 eV.
• The use of borazine prevented the formation of an amorphous SiNx interlayer at the Si interface.

Conclusions:

• A continuous flow CVD method using borazine enables the synthesis of high-quality, ultrathin hBN films on silicon.
• Spectroscopic ellipsometry is an effective tool for rapid, non-destructive characterization of hBN films.
• This approach facilitates the large-scale fabrication of hBN-based devices by overcoming previous growth challenges.