Structural and optical properties of amorphous Si-Ge-Te thin films prepared by combinatorial sputtering

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Amorphous chalcogenides possess unique properties but pose challenges in material design.
• The silicon-germanium-telluride (Si-Ge-Te) system is promising for optical data storage, sensors, and Ovonic threshold switches.
• A comprehensive exploration of the Si-Ge-Te amorphous system is lacking.

Purpose of the Study:

• To synthesize and characterize new amorphous compositions in the Si-Ge-Te system.
• To investigate the influence of composition on structural, optical, and thermal properties.
• To enable informed material selection and design for advanced applications.

Main Methods:

• Combinatorial synthesis of thin film libraries using magnetron co-sputtering.
• Investigation of compositional, structural, and optical properties.
• Analysis within the framework of topological constraint theory.

Main Results:

• Materials were classified as stressed-rigid amorphous networks.
• Bandgap is strongly dependent on tellurium (Te) content.
• A minimum in near-infrared refractive index was observed with increasing germanium (Ge) concentration, suitable for applications.
• A transition to a more ordered amorphous network occurred at 60 at% Te.
• Thermal stability and resulting crystalline phases are dictated by Ge and Te concentrations.

Conclusions:

• New amorphous compositions in the Si-Ge-Te system were discovered and their properties explored.
• The findings facilitate rapid material selection and design for specific applications.
• Topological constraint theory provides a useful framework for understanding these amorphous materials.