Computer Simulation of Multilayer Nanoparticles of Elementary Semiconductors
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2024-04-05 |
| Journal | Izvestiya of Altai State University |
| Authors | Yulia V. Terentyeva, S. Đ. Beznosyuk |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive SummaryâThis study utilized computer simulation (Non-Local Density Functional and Molecular Mechanics) to analyze the thermodynamic stability and structural parameters of 16 multilayer silicon (Si) and germanium (Ge) nanoparticles (NPs).
- Stability Hierarchy: Pure Si nanoparticles were found to be significantly more energetically stable (e.g., -390.86 kJ/mol for 3x3x3 e.c.) than pure Ge nanoparticles (-319.36 kJ/mol for 3x3x3 e.c.).
- Doping Effects: Introducing Ge atoms into Si-based systems reduces the overall thermodynamic stability, whereas introducing Si atoms into Ge-based systems increases stability.
- Bond Stabilization: The formation of Si-Ge bonds within the multilayer structure stabilizes Ge-rich particles but acts as a destabilizing factor for Si-rich particles.
- Structural Integrity: The transition from bulk diamond structure to the Nanoelectromechanical System (NEMS) state resulted in only slight, non-critical changes in interatomic distances.
- Quantified Bonds: Equilibrium parameters (energy, length, and vibrational frequency) were calculated for Si-Si, Ge-Ge, and Si-Ge dimer pairs, providing fundamental data for further modeling.
- Layer Degeneracy: Certain complex structures (Models 11/13 and 12/14, involving specific core/shell and alternating layer sequences) exhibited energy degeneracy.
Technical Specifications
Section titled âTechnical SpecificationsâThe following parameters were determined using the Non-Local Density Functional (NLDF) method and Molecular Mechanics (MM) simulations for Si and Ge semiconductor structures.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Si Lattice Constant (a) | 0.54307 | nm | Bulk diamond structure |
| Ge Lattice Constant (a) | 0.5660 | nm | Bulk diamond structure |
| Si-Si Equilibrium Bond Energy (U0) | 2.6315 | kJ/mol | Dimer pair |
| Ge-Ge Equilibrium Bond Energy (U0) | 2.1489 | kJ/mol | Dimer pair |
| Si-Ge Equilibrium Bond Energy (U0) | 2.8194 | kJ/mol | Dimer pair |
| Si-Si Equilibrium Bond Length (R0) | 4.3 | nm | Dimer pair |
| Ge-Ge Equilibrium Bond Length (R0) | 5.1 | nm | Dimer pair |
| Si-Ge Equilibrium Bond Length (R0) | 4.7 | nm | Dimer pair |
| Si-Si Zero Oscillation Frequency (Ï0) | 536 | cm-1 | Dimer pair |
| Ge-Ge Zero Oscillation Frequency (Ï0) | 235 | cm-1 | Dimer pair |
| Si-Ge Zero Oscillation Frequency (Ï0) | 426 | cm-1 | Dimer pair |
| Energy (Pure Si NP) | -390.86 | kJ/mol | 3x3x3 e.c. (216 atoms) |
| Energy (Pure Ge NP) | -319.36 | kJ/mol | 3x3x3 e.c. (216 atoms) |
| Energy (Si Shell/Ge Core NP) | -390.82 | kJ/mol | 3x3x3 e.c. (Si208Ge8) |
| Energy (Ge Shell/Si Core NP) | -326.00 | kJ/mol | 3x3x3 e.c. (Ge208Si8) |
| Energy (Pure Si NP) | -435.30 | kJ/mol | 5x5x5 e.c. (1000 atoms) |
| Energy (Pure Ge NP) | -355.54 | kJ/mol | 5x5x5 e.c. (1000 atoms) |
Key Methodologies
Section titled âKey MethodologiesâThe stability and structural properties of the multilayer Si/Ge nanoparticles were investigated using computational methods focusing on atomic-level interactions and energy minimization.
- Model Generation:
- 16 distinct nanoparticle models were constructed based on the diamond-like crystal lattice structure.
- Models varied in size (3x3x3 and 5x5x5 elementary cells, e.c.) and composition (pure Si, pure Ge, core-shell, and alternating Si-Ge layers).
- Bond Parameter Calculation (NLDF Method):
- The Non-Local Density Functional (NLDF) method was applied to determine the fundamental equilibrium parameters (bond energy, length, and vibrational frequency) for Si-Si, Ge-Ge, and Si-Ge atomic pairs within the crystal structure.
- Thermodynamic Stability Analysis (Molecular Mechanics):
- Molecular Mechanics (MM) simulations were used to model the relaxation processes of the nanoparticles.
- The resulting layer energy values were used to assess the thermodynamic stability based on particle size, overall composition, and the specific sequence of Si and Ge layers.
- Structural Characterization (RDF Analysis):
- Radial Distribution Functions (RDFs) were calculated to analyze atomic spacing and coordination spheres.
- This analysis confirmed that interatomic distances in the NEMS state showed only minor deviations from the bulk diamond structure, particularly in the first coordination sphere.
Commercial Applications
Section titled âCommercial ApplicationsâMultilayer nanoparticles based on Si and Ge are critical materials for next-generation devices, leveraging their tunable electronic and optical properties.
- Advanced Electronics:
- High-speed transistors and diodes utilizing layered structures for enhanced carrier mobility and energy efficiency.
- Development of compact, high-performance electronic devices where Si-Ge solid solutions are essential for strain engineering.
- Photonics and Optics:
- Creation of high-efficiency light sources (LEDs, lasers) and photodetectors/photocells, benefiting from improved optical characteristics due to quantum confinement effects in nanolayers.
- Nanoelectromechanical Systems (NEMS):
- Engineering stable, miniaturized mechanical and electronic components, where the controlled stability of Si-Ge interfaces is crucial for device reliability.
- Biomedical Technology:
- Use as stable nanocarriers for targeted drug delivery systems.
- Application in advanced diagnostics, potentially as contrast agents or biosensors.
- Environmental Catalysis:
- Potential use as highly efficient catalysts in chemical manufacturing or for environmental remediation (water and air purification).
View Original Abstract
The paper presents the results of computer simulations of diamond-like silicon and germanium nanoparticles, as well as layered semiconductors of various nuclearities with alternating layers. In the work, 16 models of nanoparticles with the sizes of 3-3-3 elementary cells (Đ”.Ń.) and 5-5-5 e.c. with different alternations of Si and Ge layers have been constructed. The equilibrium parameters of bonded atom pairs in the crystal structure of the studied NEMS with different morphological structures are obtained using the non-local density functional method. The dependence of the energy of the studied nanoparticles on the size, composition, and the sequence of Si and Ge alternating layers is studied by the methods of molecular mechanics. It is revealed that there are slight changes in the interatomic distance in semiconductor systems with a diamond-like structure and in the NEMS state. Systems with only Si atoms turned out to be energetically more stable than systems with only Ge atoms. The introduction of Ge atoms into Si-based systems reduces the thermodynamic stability of the particle, while it is vice versa for the Si atoms introduced into Ge-based systems. It is concluded that the appearance of the Si-Ge bonds in a nanoparticle stabilizes germanium particles and destabilizes silicon particles.