Tunable Optical Properties of Thin Films Controlled by the Interface Twist Angle

Area of Science:

• Materials Science
• Condensed Matter Physics
• Optoelectronics

Background:

• Controlling material properties is crucial for technological advancement.
• Traditional methods involve altering composition, structure, and size.
• Optical properties of materials like hexagonal boron nitride (hBN) are of significant interest.

Purpose of the Study:

• To investigate the tunability of optical properties in stacked hexagonal boron nitride (hBN) films.
• To explore the role of relative twist angles in modulating these properties.
• To demonstrate moiré phenomena in bulk-like materials at room temperature.

Main Methods:

• Utilizing cathodoluminescence spectroscopy.
• Employing a scanning transmission electron microscope.
• Analyzing stacked hexagonal boron nitride (hBN) films with varying twist angles.

Main Results:

• Continuous tuning of optical properties in stacked hBN films was achieved by altering twist angles.
• Formation of a moiré superlattice led to a tunable moiré sub-band gap.
• Luminescence wavelength was tunable, with intensity increases exceeding 40×.

Conclusions:

• Moiré phenomena are not limited to monolayer systems and can be preserved in bulk-like materials.
• Twist angle engineering offers a novel pathway to control optical properties of hBN films.
• These findings have potential applications in medicine, environmental monitoring, and information technologies.