Al2O3 on Black Phosphorus by Atomic Layer Deposition: An in Situ Interface Study

Area of Science:

• Materials Science
• Surface Chemistry
• Nanotechnology

Background:

• Black phosphorus (black-P) is a promising 2D material for electronics.
• Controlling surface chemistry is crucial for effective passivation and device fabrication.
• Atomic layer deposition (ALD) offers precise thin-film growth but requires understanding interfacial reactions.

Purpose of the Study:

• To investigate the interfacial chemistry and nucleation behavior of Al2O3 ALD on black phosphorus.
• To determine the effect of pre-existing phosphorus oxide concentrations on Al2O3 deposition.
• To understand the growth mechanism and morphology of Al2O3 on black-P.

Main Methods:

• In situ "half cycle" atomic layer deposition (ALD) of Al2O3.
• X-ray photoelectron spectroscopy (XPS) for interfacial analysis.
• Ex situ atomic force microscopy (AFM) for morphological characterization.

Main Results:

• Al2O3 nucleation on clean black-P surfaces is not detectable without pre-existing oxides.
• Pre-existing phosphorus oxides promote black-P oxidation and Al2O3 nucleation.
• Al2O3 growth exhibits substrate-inhibited behavior with an incubation period, forming islands on exfoliated black-P.

Conclusions:

• The presence of phosphorus oxides significantly influences Al2O3 ALD on black-P.
• Surface functionalization is necessary for achieving conformal Al2O3 films on oxide-free black-P.
• Understanding these interfacial reactions is key for black phosphorus device applications.