Operando Observation of Electrically Triggered Phase Transition in Thin Cu₂S Crystal

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Copper sulfide (Cu2S) is a promising material for memristors due to its multilevel resistance switching capabilities.
• The precise electroresistance mechanism in Cu2S is not fully understood, complicated by ion migration, defect evolution, and phase transitions.

Purpose of the Study:

• To investigate the electrically triggered phase transition mechanism in Cu2S.
• To elucidate the relationship between phase transition, ion migration, and resistance changes in Cu2S.

Main Methods:

• In situ transmission electron microscopy (TEM) was employed to observe the dynamic processes.
• Electrical biasing was applied at room temperature and low temperatures (-150 °C) to study phase transitions.

Main Results:

• A voltage below 1 V at room temperature induced a phase transition from γ(L)-Cu2S to β-Cu2S, altering the material's resistance.
• Electrically triggered phase transitions were also confirmed at -150 °C.
• Further voltage increase after β-Cu2S formation led to the precipitation of metallic copper nanoparticles.

Conclusions:

• Cu2S can undergo fast and controllable phase switching via electrical tuning.
• Optimizing energy consumption during phase switching is key for practical applications.
• These findings highlight the potential of Cu2S for developing low-power electronic devices like memory and sensors.