Engineering defect clustering in diamond-based materials for technological applications via quantum mechanical descriptors
At a Glance
Section titled āAt a Glanceā| Metadata | Details |
|---|---|
| Publication Date | 2025-05-12 |
| Journal | Physical Review Applied |
| Authors | MatĆŗÅ” Kaintz, Antonio Cammarata |
| Institutions | Czech Technical University in Prague |
| Citations | 1 |
| Analysis | Full AI Review Included |
Engineering Defect Clustering in Diamond-Based Materials
Section titled āEngineering Defect Clustering in Diamond-Based MaterialsāExecutive Summary
Section titled āExecutive SummaryāThis study uses first-principles calculations (DFT) to establish quantum mechanical descriptors for tuning the electronic and optical properties of diamond via controlled defect clustering.
- Core Value Proposition: Provides design rules for selecting optimal dopant types (Al, B, N, P, Si), concentrations (0.4% to 6.25%), and defect configurations (X-V, X-X, X-C-X, X-V-X) to achieve specific material functionalities.
- Key Descriptors Identified: X-C bond covalency (Cx,c), Hirshfeld charge, and orbital polarization (Pij) are crucial for predicting band gap size and semiconductor type.
- Geometry Dependence: The dopant atomic radius dictates the local coordination environment. Small dopants (B, N) preserve the vacancy (C3v), while large dopants (Al, P, Si) tend to form split-vacancy/octahedral (D3d) configurations.
- Intermediate Band (IB) Optimization: X-V-X defects (especially B, P, Si) yield the highest number of IBs (up to four energy gaps), making them the most promising candidates for high-efficiency Intermediate-Band Photovoltaics (IBSCs).
- Degenerate Semiconductors: Degenerate p-type (B-X, B-X-C-X) and n-type (P-X, P-X-X) structures were identified, achieving large optical band gaps (>4.5 eV) suitable for UV-C transparent conductive materials (TCMs).
- Activation Energy Tuning: The X-C-X cluster configuration is shown to decrease the activation energy for p-type (Al, B) and N-doped structures compared to single substitutional dopants (X).
Technical Specifications
Section titled āTechnical Specificationsā| Parameter | Value | Unit | Context |
|---|---|---|---|
| Pristine Diamond Lattice Parameter (Calculated) | 3.561 | A | DFT (GGA-WC) |
| Pristine Diamond Band Gap (Calculated) | 4.14 | eV | DFT (GGA-WC) |
| Dopant Concentrations Studied | 6.25, 1.85, 0.78, 0.4 | % | Modeled via 2x2x2 to 5x5x5 supercells |
| Plane-Wave Basis Set Energy Cutoff | 1633 | eV | DFT Simulation Parameter |
| Geometry Optimization Force Convergence | 2.5 x 10-5 | eV/A | Maximum force component |
| Maximum Optical Band Gap (p-type, B-X) | >5.0 | eV | Degenerate semiconductor, high concentration |
| Maximum Optical Band Gap (n-type, P-X) | >4.5 | eV | Degenerate semiconductor, high concentration |
| IB Energy Gap Range (IBSC candidates) | <1.5 | eV | X-V-X defects (B, P, Si) |
| X-C Bond Covalency Threshold (X-X defects) | ~-1.5 | eV | Boundary for distinguishing p-type and n-type structures |
| Activation Energy Change (X-C-X vs. X) | Decrease | N/A | Observed for Al, B, and N dopants |
Key Methodologies
Section titled āKey MethodologiesāThe study utilized first-principles calculations to analyze the coupled structural and electronic features of diamond defects.
- Computational Framework: Density-Functional Theory (DFT) implemented in the ABINIT software package.
- Energy Functional: Generalized Gradient Approximation (GGA) using the Wu-Cohen (WC) form, selected for its accuracy in reproducing diamond lattice parameters and band gap width.
- Pseudopotentials: Projected-Augmented-Wave (PAW) pseudopotentials were used with a high energy cutoff (1633 eV).
- Structural Modeling: Defects were modeled using supercells (2x2x2 to 5x5x5) to simulate concentrations from 6.25% to 0.4%. Four cluster types were investigated:
- X-V (Dopant-Vacancy)
- X-X (Nearest Neighbor Dopants)
- X-C-X (Dopants separated by one Carbon)
- X-V-X (Dopants separated by a Vacancy)
- Geometry Optimization: All atomic positions and lattice parameters were optimized until the maximum force component was below 2.5 x 10-5 eV/A.
- Electronic Structure Analysis: Calculated electronic band structures and Projected Density of States (PDOS) without spin polarization (benchmarks showed minimal geometric change with spin polarization).
- Quantum Descriptors: Used to quantify local electronic distribution and bonding:
- Hirshfeld Charges: Measure charge transfer between atoms.
- X-C Bond Covalency (Cx,c): Measures the covalent character of the dopant-carbon bond.
- Orbital Polarization (Pij): Measures the relative occupation of specific atomic orbitals (e.g., px, pz) to detail charge spatial distribution.
- Band Gap Definition: Generalized band gap (Ī) was measured as the energy difference between the Conduction Band Minimum (CBM) and the highest localized Intermediate Band (IBmax) below it, or the Fermi level (EF) for degenerate systems.
Commercial Applications
Section titled āCommercial ApplicationsāThe engineered diamond defects are promising candidates for several high-tech applications, categorized by the desired electronic properties.
| Application Category | Target Property / Goal | Optimal Dopant/Defect System |
|---|---|---|
| Transparent Conductive Materials (TCMs) | Degenerate p-type/n-type with large optical band gap (>3.1 eV, UV-C transparency) | B-X, P-X, B-X-C-X, P-X-X (All concentrations) |
| Intermediate-Band Photovoltaics (IBSCs) | Maximize number of IBs (up to 4), narrow IB width, optimal IB spacing (<1.5 eV gaps) | X-V-X defects (B, P, Si) |
| Multicolor Emitters / Optical Filters | Multiple, well-separated energy gaps | X-V-X, B-X-V, N-X-V, N-X-C-X, P-X-C-X, N-X-X, V |
| High-Conductivity Electrodes | Degenerate semiconductor (closed band gap) | B-X-V, P-X-V, Al-X-V-X, Si-X-V-X (High concentration, 6.25%) |
| Intrinsic (i-type) Semiconductors | Large energy gap, deep impurity levels (for PIN diodes) | Si-X, Si-X-C-X, Si-X-X, Al-X-X, N-X-X |
| Shallow Donor/Acceptor Doping | Low activation energy for high room-temperature conductivity | X-C-X (Al, B, N) |
View Original Abstract
Dopant-dopant and dopant-vacancy complexes in diamond can be exploited for the development of quantum computers, single-photon emitters, high-precision magnetic field sensing, and nanophotonic devices. While some dopant-vacancy complexes such as nitrogen- and silicon-vacancy centers are well studied, studies of other dopant and/or vacancy clusters are focused mainly on defect detection, with minimal investigation into their electronic features or how to tune their electronic and optical properties for specific applications. To this aim, we perform a thorough analysis of the coupled structural and electronic features of different dopant-dopant and dopant-vacancy cluster defects in diamond by means of first-principles calculations. We find that doping with <a:math xmlns:a=āhttp://www.w3.org/1998/Math/MathMLā display=āinlineā><a:mi>p</a:mi></a:math>-type (<c:math xmlns:c=āhttp://www.w3.org/1998/Math/MathMLā display=āinlineā><c:mi>n</c:mi></c:math>-type) dopant does not always lead to the creation of <e:math xmlns:e=āhttp://www.w3.org/1998/Math/MathMLā display=āinlineā><e:mi>p</e:mi></e:math>-type (<g:math xmlns:g=āhttp://www.w3.org/1998/Math/MathMLā display=āinlineā><g:mi>n</g:mi></g:math>-type) diamond structures, depending on the kind of cluster defect. We also identify the quantum mechanical descriptors that are most suitable to tune the electronic band gap about the Fermi level for each defect type. Finally, we propose how to choose suitable dopant atomic types, concentrations, and geometric environments to fabricate diamond-based materials for several technological applications such as electrodes, transparent conductive materials, intermediate-band photovoltaics, and multicolor emitters, among others.