Amorphous Ge₁₅Te₈₅: density functional, high-energy x-ray and neutron diffraction study

Area of Science:

• Materials Science
• Condensed Matter Physics
• Computational Chemistry

Background:

• Understanding the atomic structure of amorphous chalcogenides is crucial for their application in electronic devices.
• Amorphous germanium telluride (GeTe) alloys are promising materials for phase-change memory and thermoelectric applications.

Purpose of the Study:

• To elucidate the atomic structure and electronic properties of amorphous Ge(15)Te(85).
• To correlate structural features with the material's semiconducting behavior.

Main Methods:

• Combined density functional (DF) simulations with high-energy x-ray and neutron diffraction.
• Employed reverse Monte Carlo (RMC) methods to construct atomic models constrained by experimental data and theoretical principles.
• Investigated structural models for their energy and electronic band structure.

Main Results:

• The optimal structural model, derived from melt-quenched DF structures, exhibits interlocking networks of Te and GeTe with substantial void fractions (22-24%).
• Germanium atoms adopt both tetrahedral and defective octahedral configurations, while tellurium coordination slightly exceeds the '8 - N rule'.
• The GeTe network contains ABAB square clusters, and bonding is characterized by chemical bond orders.

Conclusions:

• The atomic structure of amorphous Ge(15)Te(85) is characterized by interconnected networks and significant voids.
• The observed structural motifs and coordination numbers provide insights into the material's semiconducting nature.
• This work offers a detailed atomic-level understanding of amorphous GeTe, valuable for materials design and device optimization.