A density-driven phase transition between semiconducting and metallic polyamorphs of silicon

Area of Science:

• Materials Science
• Condensed Matter Physics
• Solid-State Chemistry

Background:

• Silicon exists in crystalline and amorphous forms, with amorphous silicon typically being a semiconductor.
• High pressure reveals silicon's polymorphism, and molten silicon is a conductor.
• Amorphous silicon's liquid and solid states were speculated to be interconvertible polytypes.

Purpose of the Study:

• To provide experimental evidence for a polyamorphic transition in solid amorphous silicon.
• To investigate the link between semiconducting and metallic amorphous silicon states.
• To explore density-driven transformations in amorphous materials.

Main Methods:

• Experimental techniques to induce and observe phase transitions in amorphous silicon.
• Molecular dynamics simulations to model amorphous silicon behavior.
• Analysis of structural and electronic properties under varying conditions.

Main Results:

• Demonstrated a density-driven polyamorphic transition in solid amorphous silicon.
• Observed a transformation from a semiconducting to a metallic amorphous state.
• Simulations confirmed the mapping of amorphous solid behavior to the liquid state.

Conclusions:

• Solid amorphous silicon can undergo a polyamorphic transition, similar to liquids.
• This transition involves a change in coordination and electronic properties.
• The findings extend the understanding of polymorphism in amorphous materials.