Fermi Level Manipulation through Native Doping in the Topological Insulator Bi₂Se₃

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanotechnology

Background:

• Topological insulators (TIs) offer unique spin-polarized surface states for advanced electronics.
• Existing Bi₂Se₃ devices struggle with bulk conduction and Fermi level alignment.
• High selenium vacancy concentrations typically lead to n-type Bi₂Se₃, hindering surface state dominance.

Purpose of the Study:

• To grow near-intrinsic Bi₂Se₃ with tunable Fermi levels within the band gap.
• To enable transport dominated by topologically protected surface states.
• To provide a pathway for fabricating high-performance TI devices.

Main Methods:

• Growth of Bi₂Se₃ with minimal selenium vacancies.
• Post-growth annealing to control selenium vacancy concentration and tune Fermi level (E_F).
• Low-temperature removal of protective selenium cap for air-stable samples.

Main Results:

• Achieved near-intrinsic Bi₂Se₃ with Fermi level near midgap without extrinsic doping.
• Demonstrated precise Fermi level tuning across the band gap by controlling selenium vacancies.
• Maintained Fermi level control after air exposure, crucial for device fabrication.

Conclusions:

• Successfully suppressed bulk conduction in Bi₂Se₃ by minimizing selenium vacancies.
• Established a method for Fermi level engineering in Bi₂Se₃, essential for device applications.
• Paved the way for utilizing the unique properties of topological insulator surface states in practical devices.