High electron mobility, quantum Hall effect and anomalous optical response in atomically thin InSe.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Two-dimensional (2D) atomic crystals exhibit unique properties distinct from their bulk counterparts.
• Quantum confinement and changes in lattice symmetry significantly alter electronic band structures.

Purpose of the Study:

• To investigate the electronic and optical properties of high-quality few-layer indium selenide (InSe) encapsulated in hexagonal boron nitride.
• To explore the potential of 2D InSe as a material for advanced electronic devices.

Main Methods:

• Fabrication of encapsulated few-layer InSe using hexagonal boron nitride.
• Electrical transport measurements at room and cryogenic temperatures.
• Photoluminescence spectroscopy to study bandgap evolution.

Main Results:

• Achieved carrier mobilities exceeding 10³ cm²/Vs at room temperature and 10⁴ cm²/Vs at liquid-helium temperature.
• Observed the quantum Hall effect, indicating a high-quality 2D electron gas occupying a single subband with small effective mass.
• Demonstrated a significant increase in bandgap (>0.5 eV) from bulk to bilayer InSe, with vanishing optical response in monolayer InSe due to symmetry.

Conclusions:

• Encapsulated 2D InSe is a promising graphene-like semiconductor with properties competitive with other advanced 2D materials.
• The observed high carrier mobility and tunable bandgap open avenues for novel electronic and optoelectronic applications.