Pressure-dependent bandgap study of MBE grown {CdO/MgO} short period SLs using diamond anvil cell
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2022-12-12 |
| Journal | Applied Physics Letters |
| Authors | A. Adhikari, PaweĆ StrÄ k, P. DĆuĆŒewski, Agata KamiĆska, E. PrzeĆșdziecka |
| Institutions | Institute of High Pressure Physics, Cardinal Stefan WyszyĆski University in Warsaw |
| Citations | 2 |
| Analysis | Full AI Review Included |
Technical Analysis and Documentation: High-Pressure Bandgap Engineering using Diamond Anvil Cells
Section titled âTechnical Analysis and Documentation: High-Pressure Bandgap Engineering using Diamond Anvil CellsâExecutive Summary
Section titled âExecutive SummaryâThis research investigates the pressure-dependent optical properties of short-period {CdO/MgO} superlattices (SLs), a critical step for developing advanced optoelectronic devices and pressure sensors. The study relies heavily on the performance and optical quality of the Diamond Anvil Cell (DAC) components, a core application area for 6CCVDâs Single Crystal Diamond (SCD).
- Core Achievement: Successful measurement of the fundamental direct bandgap shift in {CdO/MgO} SLs under hydrostatic pressure ranging from 0 to 5.9 GPa.
- Key Finding: The direct bandgap widens linearly with pressure, shifting from 2.76 eV (ambient) to 2.87 eV (maximum pressure).
- Pressure Coefficient (PC): The experimental linear pressure coefficient was determined to be 26 meV/GPa, confirming the materialâs suitability for pressure-sensitive applications.
- Methodology: Plasma-Assisted Molecular Beam Epitaxy (PA-MBE) growth followed by optical absorption spectroscopy using a high-quality Diamond Anvil Cell (DAC).
- Material Relevance: The integrity and optical transparency of the diamond anvils are paramount for accurate UV-Vis absorption measurements under extreme pressure, directly correlating to 6CCVDâs high-purity SCD product line.
- Future Applications: The findings provide valuable insight for bandgap engineering and the design of next-generation pressure sensors and ultrafast optoelectronics.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the experimental and theoretical results presented in the paper:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Experimental Pressure Range | 0 to 5.9 | GPa | Applied hydrostatic pressure via DAC |
| Ambient Direct Bandgap (Eg(0)) | 2.761 ± 0.002 | eV | Measured at 0 GPa (Room Temperature) |
| Maximum Measured Direct Bandgap | 2.87 | eV | Measured at 5.9 GPa |
| Experimental Pressure Coefficient (ap) | 26 ± 2 | meV/GPa | Linear fit of Eg(P) up to 4.3 GPa (Î-Î transition) |
| Theoretical Pressure Coefficient (ap) | 32 | meV/GPa | Calculated for ideal SLs (Î-Î transition) |
| Bulk Modulus (B) | 156.6 | GPa | Calculated for {CdO/MgO} SLs |
| Pressure Derivative of Bulk Modulus (Bâ) | 4.75 | Dimensionless | Calculated for {CdO/MgO} SLs |
| Volume Deformation Potential (av) | -5.05 | eV | Calculated for direct transition (Î-Î) |
| CdO Bulk Modulus (Literature Range) | 130 to 166 | GPa | Comparison data |
| MgO Bulk Modulus (Literature Range) | 171 to 186 | GPa | Comparison data |
Key Methodologies
Section titled âKey MethodologiesâThe study combined advanced epitaxial growth with high-pressure optical characterization and theoretical modeling:
- Superlattice Growth: Short-period {CdO/MgO} SLs were grown on an r-plane (1-102) sapphire substrate.
- Epitaxy Technique: Plasma-assisted Molecular Beam Epitaxy (PA-MBE) was utilized to achieve precise control over layer thickness and interface quality.
- Structural Confirmation: High-resolution Transmission Electron Microscopy (HR-TEM) and Energy-Dispersive X-ray Spectroscopy (EDX) mapping confirmed the distinct separation and quality of the CdO and MgO layers.
- High-Pressure Setup: Optical absorption measurements were performed using a Diamond Anvil Cell (DAC) to apply hydrostatic pressure up to 5.9 GPa.
- Optical Measurement: UV-Vis spectroscopy was used to measure transmittance spectra. The direct bandgap was determined by extrapolating the linear portion of the Tauc plot (a2 vs. photon energy).
- Pressure Calibration: Pressure within the DAC was monitored using the standard ruby luminescence method.
- Theoretical Modeling: Density Functional Theory (DFT) calculations, specifically using the GGA-1/2 correction method, were employed to model the electronic band structure, pressure coefficients, bulk modulus, and volume deformation potential, supporting the experimental data.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe successful execution of this high-pressure optical study critically depends on the quality and precision of the diamond anvils used in the DAC. 6CCVD is uniquely positioned to supply the high-performance MPCVD diamond materials necessary to replicate and advance this research, particularly in the fields of high-pressure physics and diamond-based sensing.
| Research Requirement / Application | 6CCVD Material Recommendation | Specific Capability & Sales Advantage |
|---|---|---|
| Diamond Anvil Cell (DAC) Anvils | Optical Grade Single Crystal Diamond (SCD) | Our SCD is grown via MPCVD, offering superior purity (Type IIa equivalent) and exceptional transparency across the UV-Vis spectrum (220 nm to far-IR), minimizing signal loss and noise in absorption measurements under pressure. |
| Precision Geometry & Finish | Custom Laser Cutting and Ultra-Polishing Services | We provide custom dimensions for plates/wafers up to 125mm. Crucially, we achieve surface roughness Ra < 1 nm on SCD, essential for the precise seating and sealing required to maintain hydrostatic pressure up to 6 GPa and beyond. |
| High-Pressure Sensing Integration | Heavy Boron-Doped Diamond (BDD) | For extending this research into functional pressure sensors (as suggested by the authors), BDD is the ideal piezoresistive material. We offer BDD films (0.1 ”m to 500 ”m) for direct integration onto high-pressure membranes or substrates. |
| Metalization for Electrical Contacts | Custom Metalization Services (Au, Pt, Ti, W) | If future experiments require electrical contacts on the diamond anvils or gaskets (e.g., for simultaneous electrical and optical measurements), 6CCVD offers in-house deposition of standard and refractory metals. |
| Large-Scale High-Pressure Research | Polycrystalline Diamond (PCD) Plates | For applications requiring larger sample volumes or lower optical constraints, we offer PCD plates up to 125mm in diameter with polishing down to Ra < 5 nm. |
| Engineering Consultation | In-house PhD Material Science Team | Our experts can assist researchers in selecting the optimal diamond orientation, thickness (SCD up to 500 ”m), and doping level to maximize performance in high-pressure optical or electronic device fabrication projects. |
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Semiconductor superlattices (SLs) have found widespread applications in electronic industries. In this work, a short-period SL structure composed of CdO and MgO layers was grown using a plasma-assisted molecular beam epitaxy technique. The optical property of the SLs was investigated by absorption measurement at room temperature. The ambient-pressure direct bandgap was found to be 2.76 eV. The pressure dependence of fundamental bandgap has been studied using a diamond anvil cell technique. It has been found that the band-to-band transition shifts toward higher energy with an applied pressure. The bandgap of SLs was varied from 2.76 to 2.87 eV with applied pressure varied from 0 to 5.9 GPa. The pressure coefficient for the direct bandgap of SLs was found to be 26 meV/GPa. The obtained experimental result was supported by theoretical results obtained using density functional theory calculations. The volume deformation potential was estimated using the empirical rule. We believe that our findings may provide valuable insight for a better understanding of {CdO/MgO} SLs toward their future applications in optoelectronics.