Gate-Tunable Giant Stark Effect in Few-Layer Black Phosphorus.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanotechnology

Background:

• Two-dimensional black phosphorus (BP) exhibits high carrier mobility, layer-dependent bandgap, and anisotropic properties.
• BP allows for bandgap tuning across visible to infrared spectra.
• The unique properties of BP make it a promising material for novel electronic and photonic applications.

Purpose of the Study:

• To investigate the Stark effect in electrostatically gated few-layer black phosphorus (BP).
• To explore the potential of BP for developing tunable optoelectronic devices.

Main Methods:

• Utilized low-temperature scanning tunneling microscopy (LT-STM) for high-resolution imaging and spectroscopy.
• Employed electrostatic gating to control carrier concentration and modulate the bandgap.
• Probed the local density of states (LDOS) using tunneling spectroscopy.

Main Results:

• Observed a giant Stark effect in few-layer BP under electrostatic gating.
• Demonstrated monotonic bandgap reduction upon electron injection, compensating defect-induced holes.
• Achieved up to 35.5% bandgap modulation in the light-doping regime.
• Identified characteristic resonance features in LDOS due to quantum confinement and sub-band structures.

Conclusions:

• The electrical gate-controlled giant Stark effect in BP is demonstrated.
• This finding opens avenues for designing electro-optic modulators and photodetectors.
• BP-based devices could operate across a wide electromagnetic spectral range.