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Liquid-liquid phase transition in quasi-two-dimensional supercooled silicon
1National Engineering Research Central for Rare Earth Materials, General Research Institute for Non-Ferrous Metals, GRIREM Advanced Co. Ltd., Beijing 100088, China.
Physical Chemistry Chemical Physics : PCCP
|July 23, 2014
Summary
Cooling quasi-two-dimensional liquid silicon reveals a liquid-liquid phase transition (LLPT) marked by crystal-like structures. These structures precede the liquid-solid phase transition, influencing electronic properties in 2D silicon.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Physical Chemistry
Background:
- Understanding phase transitions in low-dimensional materials is crucial for advanced electronics.
- Quasi-two-dimensional liquid silicon exhibits unique structural behaviors upon cooling.
- Previous studies on bulk liquid silicon show overlapping phase transitions.
Purpose of the Study:
- To investigate anomalies in the local structural order of quasi-two-dimensional liquid silicon during cooling.
- To identify the structural signatures of phase transitions in this system.
- To elucidate the relationship between structural changes and electronic property transitions.
Main Methods:
- Analysis of pair correlation functions to detect structural changes.
- Investigation of local structural order and paracrystalline region formation.
- Comparison of phase transition stages in quasi-two-dimensional versus bulk liquid silicon.
Main Results:
- The appearance of a left subpeak in pair correlation functions signifies the liquid-liquid phase transition (LLPT).
- LLPT in quasi-two-dimensional liquid silicon involves the formation of short-range, crystal-like ordered structures.
- The LLPT and liquid-solid phase transition (LSPT) stages are distinct and do not overlap, with LLPT structures acting as precursors to LSPT.
- A strong link exists between paracrystalline regions and the metal-to-semimetal transition in 2D silicon.
Conclusions:
- The LLPT in quasi-two-dimensional liquid silicon is characterized by the formation of ordered, crystal-like precursors.
- The non-overlapping nature of LLPT and LSPT simplifies the understanding of phase changes in 2D silicon.
- The observed structural changes are directly correlated with the electronic transition from metallic to semimetallic states.
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