The occupied electronic structure of ultrathin boron doped diamond
At a Glance
Section titled āAt a Glanceā| Metadata | Details |
|---|---|
| Publication Date | 2020-01-01 |
| Journal | Nanoscale Advances |
| Authors | A. C. Pakpour-Tabrizi, Alex K. Schenk, Ann Julie Holt, Sanjoy Kr Mahatha, Fabian Arnold |
| Institutions | Russian Academy of Sciences, Norwegian University of Science and Technology |
| Citations | 10 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled āExecutive Summaryā- Objective: To compare the occupied electronic band structure of an ultrathin (1.8 nm) boron-doped diamond (BDD) delta-layer (Ī“-layer) against a bulk (3 Āµm) BDD film using Angle-Resolved Photoelectron Spectroscopy (ARPES).
- Core Finding: The electronic structure of the nanoscale BDD Ī“-layer is highly similar to that of the bulk BDD, indicating that the desirable bulk properties are retained at the nanometer scale.
- Quantum Confinement (QC): Contrary to theoretical predictions, no occupied quantum well states resulting from QC were observed in the 1.8 nm BDD Ī“-layer.
- Effective Mass Modification: A small, but significant, difference in the hole effective mass was detected in the Ī“-layer compared to the bulk film, attributed to electron-electron correlation effects (bandwidth narrowing).
- Engineering Advantage: Current CVD processing techniques can produce nanoscale BDD structures that retain classical bulk electronic properties, eliminating the need to account for complex quantum confinement effects during device miniaturization.
Technical Specifications
Section titled āTechnical Specificationsā| Parameter | Value | Unit | Context |
|---|---|---|---|
| Thin Film Thickness (Nominal) | 1.8 | nm | Boron-doped Ī“-layer (approx. 8 atomic layers) |
| Bulk Film Thickness | 3 | Āµm | Comparison sample |
| Intrinsic Buffer Layer Thickness | 0.5 | Āµm | Grown via CVD |
| Boron Doping Density (Nominal) | ~5 x 1020 | cm-3 | Measured by SIMS (Similar for both samples) |
| Substrate Orientation | (100) | N/A | High Pressure High Temperature (HPHT) Ib Diamond |
| ARPES Photon Energy Range | 380 - 460 | eV | Used to probe the bulk Brillouin Zone center (Ī) |
| Inner Potential (Diamond) | 22 | eV | Used for kā„ conversion in ARPES analysis |
| In Situ Annealing (Long) | 350 | Ā°C | 8 hours, for atmospheric contamination removal |
| In Situ Annealing (Flash) | 800 | Ā°C | Multiple 5-second flashes |
| Calculated Light Hole Mass (mlh) | 0.263 - 0.309 | mo | Range of literature values for bulk diamond |
| Calculated Heavy Hole Mass (mhh) | 0.588 - 0.653 | mo | Range of literature values for bulk diamond |
Key Methodologies
Section titled āKey Methodologiesā- Sample Growth (CVD): The ultrathin 1.8 nm boron-doped Ī“-layer was grown using Chemical Vapour Deposition (CVD) on a HPHT Ib (100) diamond substrate, preceded by a 0.5 Āµm intrinsic diamond buffer layer.
- Dopant Profiling (SIMS): Secondary-Ion Mass Spectrometry (SIMS) was used to confirm the heavy boron doping concentration (~5 x 1020 cm-3) and to estimate the depth profile sharpness, which was found to be similar to high-quality Si:P Ī“-layers.
- In Situ Surface Preparation: Samples were prepared in ultra-high vacuum (UHV) by annealing at 350 Ā°C for 8 hours, followed by multiple 5-second flashes to 800 Ā°C, ensuring a pristine surface free of atmospheric adsorbates (which can significantly alter surface doping).
- Electronic Structure Mapping (ARPES): Angle-Resolved Photoelectron Spectroscopy was performed at high photon energies (380-460 eV) to map the occupied electronic band structure, specifically focusing on the dispersion relation E(k).
- Energy Calibration: Absolute energy calibration was performed by aligning the Fermi edge of a gold foil reference and compensating for potential Schottky barriers or photovoltage effects induced by synchrotron light exposure.
- Theoretical Modeling (TB): Tight Binding (TB) calculations were used to model the bulk band structure and were overlaid onto the experimental data to facilitate comparison and analysis of the observed effective mass changes.
Commercial Applications
Section titled āCommercial Applicationsā- Miniaturized High-Power Electronics: Diamondās high thermal conductivity and high breakdown field are retained at the nanoscale, enabling the development of highly efficient, miniaturized electrical components (e.g., power transistors, RF devices) that are not limited by quantum confinement effects common in downscaled silicon.
- Advanced Superconducting Components: Boron-doped diamond is a known superconductor. The ability to control the effective mass in ultra-thin layers provides a pathway for engineering the electron-phonon coupling strength, potentially optimizing the critical temperature (Tc) for use in superconducting quantum circuits.
- Radiation-Hard Sensors and Electronics: Diamondās inherent radiation hardness, combined with the ability to maintain bulk electronic performance in nanoscale films, makes this technology ideal for robust electronics used in harsh environments (e.g., nuclear facilities, space exploration).
- Piezoresistive Diamond Sensors: The persistence of bulk-like electronic properties in thin films supports the development of highly sensitive and stable miniaturized piezoresistive sensors (pressure/strain gauges) for industrial and medical applications.
- Delta-Doping Architectures: The successful fabrication and characterization of heavily doped, sharp Ī“-layers in diamond validates the processing techniques necessary for creating advanced 3D dopant architectures, critical for next-generation semiconductor device design.
View Original Abstract
Using angle-resolved photoelectron spectroscopy, we compare the electronic band structure of an ultrathin (1.8 nm) Ī“-layer of boron-doped diamond with a bulk-like boron doped diamond film (3 Ī¼m).