Large substitutional impurity isotope shift in infrared spectra of boron-doped diamond
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2020-10-16 |
| Journal | Physical review. B./Physical review. B |
| Authors | D. D. Prikhodko, С.Г. Павлов, С. А. Тарелкин, В. С. Бормашов, М. С. Кузнецов |
| Institutions | Technological Institute for Superhard and Novel Carbon Materials, National University of Science and Technology |
| Citations | 6 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Isotope Splitting in Boron-Doped Diamond
Section titled “Technical Documentation & Analysis: Isotope Splitting in Boron-Doped Diamond”Executive Summary
Section titled “Executive Summary”This research successfully resolves the isotopic splitting of boron-related intracenter transitions in diamond, a critical step for advanced diamond electronics and optics. The findings underscore the necessity of ultra-high-purity, isotopically controlled diamond materials, a core capability of 6CCVD.
- Breakthrough Isotopic Resolution: The study achieved the largest impurity isotopic shift ever observed in hydrogen-like doped semiconductors (0.7 ± 0.03 meV) by resolving the distinct spectral lines of 10B and 11B isotopes in Boron-Doped Diamond (BDD).
- Material Quality Requirement: Resolution was dependent on using high-quality, moderately doped single crystal diamond (SCBDD) with low compensation (residual nitrogen <1015 cm-3) and high crystalline perfection (specifically the (001) growth sector).
- Dominant Broadening Mechanism: The IR absorption lines exhibited a quasi-Lorentzian shape, indicating that homogeneous broadening (multi-phonon interaction) dominates over concentration broadening, even at moderate doping levels (~1016 cm-3).
- Derived Optical Parameters: Accurate determination of integrated absorption cross-sections and oscillator strengths was achieved, leading to the estimation of short excited state lifetimes (1-9 ps).
- 6CCVD Value Proposition: 6CCVD specializes in MPCVD growth, offering superior purity, size, and isotopic control compared to the HPHT method used in this paper, enabling the replication and extension of this high-resolution spectroscopy research.
Technical Specifications
Section titled “Technical Specifications”The following hard data points were extracted from the research paper, detailing the experimental conditions and key results:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Isotopic Splitting (Chemical Shift) | 0.70 ± 0.03 | meV | Energy separation between 10B and 11B transitions. |
| Spectrometer Resolution | 0.03 (0.25) | meV (cm-1) | High resolution required to resolve isotopic doublets. |
| Measurement Temperature | 5 | K | Required to minimize thermal broadening and exclude 1Γ7+ transitions. |
| Boron Concentration (Uncompensated) | 7·1015 to 3·1017 | cm-3 | Moderate doping range (40 ppb - 2 ppm) used to limit concentration broadening. |
| Sample Thickness Range | 152 to 385 | µm | Thickness of the (001)-oriented SCBDD plates. |
| Excited State Lifetimes (τ) | 1 to 9 | ps | Derived from FWHM using the uncertainty principle. |
| Boron Binding Energy (Ionization Energy) | 371.09 to 371.46 | meV | Restricted range based on high-energy transition analysis. |
| Hole Effective Mass (m*) used in calculation | 0.63 | m0 | Value used to calculate oscillator strength (Note: highly uncertain). |
Key Methodologies
Section titled “Key Methodologies”The experiment relied on high-quality material synthesis and precise low-temperature spectroscopy:
- Material Growth: Single Crystal Boron-Doped Diamond (SCBDD) was grown using the High Pressure High Temperature (HPHT) temperature gradient method.
- Isotopic Control: Two types of boron sources were used: natural isotopic content (80% 11B + 20% 10B) and boron oxide (B2O3) enriched up to 99% 11B.
- Sample Preparation: (001)-oriented plates (~300 µm thick) were laser-cut from the top growth sector, which provides the most uniform dopant distribution.
- Polishing: Plates were double-side polished with a deliberate wedge (~1°) to suppress optical interference effects during IR measurements.
- Concentration Determination: Boron concentration was estimated from 300 K absorption spectra using empirical integrated absorption calibration, focusing on uncompensated acceptor centers.
- Spectroscopy Setup: High-resolution Fourier-transform IR spectroscopy (Bruker Vertex 80v™) was employed, utilizing a Janis flow helium cryostat to maintain temperatures down to 5 K.
- Data Analysis: Absorption lines were approximated using a Lorentz function, confirming dominant uniform (homogeneous) broadening, allowing for accurate calculation of optical parameters.
6CCVD Solutions & Capabilities
Section titled “6CCVD Solutions & Capabilities”6CCVD’s advanced MPCVD diamond synthesis capabilities are ideally suited to meet and exceed the material requirements for replicating and advancing this high-resolution spectroscopic research.
Applicable Materials
Section titled “Applicable Materials”The success of this research hinges on minimizing impurity and lattice disorder. 6CCVD provides materials engineered for this purpose:
| Research Requirement | 6CCVD Solution | Material Specification |
|---|---|---|
| High Purity & Low Compensation | Optical Grade Single Crystal Diamond (SCD) | Ultra-low nitrogen incorporation (<1015 cm-3) ensures minimal deep donor compensation, crucial for resolving fine spectral features. |
| Controlled Boron Doping | Boron-Doped Diamond (BDD) | Precise, uniform doping control (down to ppb levels) via MPCVD allows for the exact replication of the required concentration range (7·1015 to 3·1017 cm-3) while maintaining high crystalline quality. |
| Isotopic Enrichment | Custom Isotopic BDD | 6CCVD offers custom synthesis using isotopically enriched precursors (e.g., 11B or 10B) to produce materials with controlled isotopic ratios, essential for isolating specific transition lines and confirming chemical shifts. |
Customization Potential
Section titled “Customization Potential”The paper utilized specific dimensions and preparation techniques that 6CCVD can readily match or improve upon:
- Custom Dimensions and Orientation: The paper used (001)-oriented plates (~300 µm thick). 6CCVD provides SCD wafers in custom orientations and thicknesses ranging from 0.1 µm up to 500 µm.
- Precision Polishing: The samples required double-side polishing with a wedge to suppress interference. 6CCVD offers ultra-smooth polishing (Ra < 1 nm for SCD), ensuring optimal optical transmission and minimal surface scattering for high-resolution IR experiments. We can accommodate custom wedge angles upon request.
- Advanced Fabrication: While not used in this study, 6CCVD offers custom metalization services (Au, Pt, Pd, Ti, W, Cu). For future integration into electronic or optoelectronic devices based on these fundamental transitions, our in-house capabilities ensure seamless material-to-device fabrication.
Engineering Support
Section titled “Engineering Support”The theoretical analysis in the paper highlights the uncertainty in key parameters, such as the hole effective mass (m*), which impacts the derived oscillator strengths.
6CCVD’s in-house PhD team specializes in the fundamental physics and material science of diamond. We offer comprehensive engineering support to assist researchers in:
- Material Selection: Optimizing BDD concentration and isotopic purity for specific spectroscopic applications (e.g., minimizing line broadening for quantum sensing or maximizing absorption cross-section for IR detectors).
- Advanced Characterization: Providing detailed pre-shipment characterization data (e.g., Raman, PL, SIMS) to ensure the material meets the stringent requirements for high-resolution intracenter transition spectroscopy projects.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Isotopic enrichment offers cutting-edge properties of materials opening exciting research and development opportunities. In semiconductors, reached progress of ultimate control in growth and doping techniques follows nowadays the high level isotopic purification. This requires deep understanding of isotopic disorder effects and techniques of their effective determination. Isotopic content of both crystal lattice and impurity centers cause the effects, which can be examined by different optical techniques. While disorder in the host lattice can be straight forward evaluated by inelastic light scattering or by SIMS measurements, determination of isotopic contributions of many orders less presented impurities remains challenging and usually observed in high-resolution photoluminescence or optical absorption spectra. Boron-doped diamonds exhibit complex infrared absorption spectra while boron-related luminescence remains unobserved. Boron, as a most light element acting as a hydrogen-like dopant in elemental semiconductors, has a largest relative difference in its isotope masses, and by this, cause the largest isotopic disorder in semiconductors, including diamond, an elemental semiconductor with the lightest atomic mass of a host lattice. This enables an access to the isotopic constitution of boron in diamond by infrared absorption spectroscopy. By comparison of low-temperature absorption spectra of a natural (20% of 10B and 80% of 11B isotopes) and 11B enriched (up to 99%) doped diamonds we differentiate the intracenter transitions related to 10B and to 11B isotopes. We have found that the isotopic spectral lines of the same boron intracenter transition are separated with the energy of about 0.7 meV. This is the largest impurity isotopic shift ever observed in semiconductors doped by hydrogen-like impurity centers.
Tech Support
Section titled “Tech Support”Original Source
Section titled “Original Source”References
Section titled “References”- 2012 - Handbook of Spectral Lines in Diamond [Crossref]