Electronic Structure and Band Alignment at the NiO and SrTiO₃ p-n Heterojunctions

Area of Science:

• Materials Science
• Solid State Physics
• Device Physics

Background:

• Designing oxide interfaces with controllable properties is crucial for advanced optoelectronic devices.
• Understanding interfacial energetics like band alignment and built-in potentials is a key challenge.

Purpose of the Study:

• Investigate the heterointerface of wide-band-gap p-type NiO and n-type SrTiO3 (STO).
• Explore the epitaxial growth of NiO and Li-doped NiO (LNO) on STO substrates.
• Characterize the electronic and structural properties of NiO/STO and LNO/NbSTO heterojunctions.

Main Methods:

• Epitaxial thin film growth using domain-matching epitaxy.
• X-ray photoelectron spectroscopy (XPS) for band alignment determination.
• Electrical characterization of p-n heterojunctions.

Main Results:

• High-quality NiO and LNO films grown on STO despite lattice mismatch.
• NiO/STO heterojunctions exhibit a type II staggered band alignment.
• LNO/NbSTO heterojunctions show a large built-in potential (0.97 eV), high rectification ratio (2 × 10^3), and ideality factor (4.3).

Conclusions:

• The NiO/STO interface offers favorable energetics for efficient photogenerated charge separation and transport.
• These findings have significant implications for developing novel photocatalysis and photodetector devices.
• Domain-matching epitaxy is a viable strategy for fabricating high-quality oxide heterostructures.