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Published on: January 19, 2018
First-principles study of nitrogen doping in cubic and amorphous Ge2Sb2Te5
S Caravati1, D Colleoni, R Mazzarello
1Computational Science, Department of Chemistry and Applied Biosciences, ETH Zurich, USI Campus, Via Giuseppe Buffi 13, CH-6900 Lugano, Switzerland.
Summary
Nitrogen doping in germanium-antimony-telluride (Ge2Sb2Te5) materials primarily occurs in molecular form. This segregation at grain boundaries during crystallization influences grain size and raises the crystallization temperature.
Area of Science:
- Materials Science
- Computational Materials Science
- Solid State Physics
Background:
- Germanium-antimony-telluride (Ge2Sb2Te5) is a key phase-change material used in data storage.
- Understanding dopant behavior is crucial for optimizing material properties.
- Nitrogen (N) doping is explored to modify the crystallization and structural characteristics of Ge2Sb2Te5.
Purpose of the Study:
- To investigate the structural, electronic, and vibrational properties of amorphous and cubic Ge2Sb2Te5 doped with nitrogen.
- To determine the energetic feasibility of nitrogen incorporation in different forms (atomic vs. molecular) and phases (amorphous vs. crystalline).
Main Methods:
- Large-scale ab initio simulations were employed to model the material.
- Analysis focused on the energy costs associated with nitrogen insertion in various configurations.
Main Results:
- Nitrogen can be incorporated in molecular form in both amorphous and crystalline Ge2Sb2Te5 with moderate energy cost.
- Atomic nitrogen incorporation is energetically unfavorable in the crystalline phase but possible in the amorphous phase.
- Simulations support nitrogen segregation at grain boundaries during crystallization.
Conclusions:
- Nitrogen doping in Ge2Sb2Te5 favors molecular incorporation, particularly at grain boundaries.
- This segregation leads to smaller crystalline grain sizes and an elevated crystallization temperature.
- The findings provide insights into the mechanism of nitrogen doping in phase-change materials.
