Nanoscale phase separation in the oxide layer at GeTe (111) surfaces

Area of Science:

• Materials Science
• Solid-State Physics
• Surface Chemistry

Background:

• Germanium telluride (GeTe) is a semiconductor ferroelectric with applications in thermoelectrics and data storage.
• Recent discovery of giant Rashba splitting has renewed interest in GeTe.
• Surface oxidation stability is crucial for GeTe device processing and operation.

Purpose of the Study:

• Investigate the reaction kinetics and oxide layer structure of GeTe (111) surfaces upon exposure to molecular oxygen.
• Understand the influence of ferroelectric properties and domain structure on oxidation behavior.

Main Methods:

• Ex situ and in situ Near Ambient Pressure X-ray Photoelectron Spectroscopy (NAP XPS) for reaction kinetics.
• High-Angle Annular Dark-Field Scanning Transmission Electron Microscopy (HAADF-STEM) for structural analysis.
• Scanning Transmission Electron Energy-Dispersive X-ray Spectroscopy (STEM-EDX) for elemental mapping.

Main Results:

• Observed nanoscale phase separation of GeO2 and Te in the oxide layer, an unusual phenomenon for semiconductors.
• Evaluated reaction kinetics of GeTe oxidation under controlled oxygen exposure.
• Characterized the detailed structure of the oxide layer formed on GeTe (111).

Conclusions:

• The observed nanoscale phase separation of GeO2 and Te is potentially linked to the ferroelectric properties and domain structure of GeTe.
• Findings provide insights into the surface chemistry and oxidation mechanisms of GeTe.
• Understanding these oxidation behaviors is critical for the development of GeTe-based devices.