Effect of boron doping on luminescent properties of silicon--vacancy and germanium--vacancy color centers in diamond particles obtained by chemical vapor deposition
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2022-01-01 |
| Journal | Физика твердого тела |
| Authors | S. A. Grudinkin, Н. А. Феоктистов, Kirill Bogdanov, А. В. Баранов, V. G. Golubev |
| Institutions | Ioffe Institute, ITMO University |
| Citations | 1 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled “Executive Summary”This research investigates the impact of boron (B) doping on the photoluminescent (PL) properties of Silicon-Vacancy (SiV) and Germanium-Vacancy (GeV) color centers embedded in diamond particles (DPs) synthesized via Hot Filament Chemical Vapor Deposition (HFCVD).
- Sensitive Doping Indicator: The intensity of the narrow Zero-Phonon Line (ZPL) of the SiV center (738.2 nm) exhibits a strong dependence on low concentrations of boron atoms, making SiV centers a highly sensitive indicator for detecting B incorporation into the diamond lattice.
- Luminescence Quenching: Increasing the B/C ratio in the gas phase from 0 to 46 ppm results in a significant quenching of both SiV and GeV ZPL intensities, attributed to B atoms occupying vacancies necessary for center formation or shifting the Fermi level, changing the charge state.
- Broadband PL Peak: The integral intensity of the broadband PL (520-800 nm), associated with structural defects and donor-acceptor pairs, maximizes at a gas phase B/C ratio of approximately 46 ppm.
- Fano Resonance Observed: At high B doping levels (64000 ppm B/C gas), the diamond Raman band exhibits a spectral response characteristic of the Fano resonance, confirming the formation of a continuum of electronic states (free holes) due to high B concentration (~1.1 x 1021 cm-3).
- Structural Stability at Low Doping: Raman spectra show that the crystal structure of DPs remains virtually unchanged up to a B/C gas ratio of 1540 ppm, indicating that structural disorder only becomes significant at very high doping levels.
Technical Specifications
Section titled “Technical Specifications”| Parameter | Value | Unit | Context |
|---|---|---|---|
| SiV ZPL Wavelength | 738.2 | nm | Negative charge state |
| GeV ZPL Wavelength | 602.3 | nm | Negative charge state |
| HFCVD Coil Temperature | 2000-2200 | °C | Synthesis parameters |
| Operating Pressure | 48 | Torr | Synthesis parameters |
| Hydrogen Consumption | 480 | sccm | Synthesis parameters |
| Methane Concentration | 4 | % | Synthesis parameters |
| Diamond Growth Time | 3 | h | Synthesis parameters |
| B/C Ratio (Gas Phase) | 14 to 64000 | ppm | Range of diborane doping |
| Broadband PL Range | 520-800 | nm | Observed wide luminescence band |
| Broadband PL Peak (B/C) | ≈ 46 | ppm | Gas ratio where integral PL intensity is maximum |
| Diamond Raman Band (Undoped) | ~1332 | cm-1 | F2g optical phonon mode |
| Diamond Raman Band FWHM (Undoped) | ~7 | cm-1 | Spectral width at low doping |
| Diamond Raman Band (Highly Doped) | 1322 | cm-1 | Shifted position at 64000 ppm B/C gas |
| Diamond Raman Band FWHM (Highly Doped) | ~23 | cm-1 | Spectral width at 64000 ppm B/C gas |
| Estimated B Concentration (Lattice) | ~1.1 x 1021 | cm-3 | Calculated from Raman shift at 64000 ppm B/C gas |
| Synthesized DP Size | 0.9 to 1.5 | µm | Measured by Atomic Force Microscopy (AFM) |
| Nucleation Center Size | ~4 | nm | Detonation nanodiamonds used |
Key Methodologies
Section titled “Key Methodologies”The diamond particles (DPs) were synthesized using the Hot Filament Chemical Vapor Deposition (HFCVD) technique, followed by detailed optical characterization.
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Synthesis Setup:
- Method: Hot Filament Chemical Vapor Deposition (HFCVD).
- Substrates: Crystalline silicon (Si source) and crystalline germanium plate (Ge source) were placed near the substrate holder.
- Nucleation: Detonation nanodiamonds (~4 nm size) were deposited on the Si substrate surface (~107 cm-2 density).
- Gas Mixture: Hydrogen (H2), Methane (CH4, 4% concentration), and Diborane (B2H6) as the boron source.
- Doping Control: The B/C ratio in the gas mixture was varied widely, from 14 ppm to 64000 ppm.
- Color Center Formation: Si and Ge atoms were introduced via etching of the solid-state sources by atomic hydrogen, forming volatile radicals (SiHx, GeHx) that were subsequently embedded into the growing diamond lattice.
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Characterization Techniques:
- Raman Scattering (RS) and Photoluminescence (PL): Measured in backscatter geometry using a Renishaw InVia micro-Raman spectrometer with a confocal microscope.
- Excitation Source: 488 nm laser wavelength.
- Focusing: 100x objective (NA = 0.9), spot diameter ~1 µm.
- Measurement Conditions: Room temperature, recorded from single isolated DPs.
- Data Analysis (High Doping): The RS spectra of highly boron-doped DPs were analyzed using the Fano resonance model to decompose individual bands and estimate the concentration of substitutional boron atoms.
Commercial Applications
Section titled “Commercial Applications”The ability to precisely control the incorporation of boron and its resulting effect on SiV and GeV color centers opens several avenues for advanced diamond applications:
| Application Area | Technological Relevance | Role of Boron/Color Centers |
|---|---|---|
| Quantum Information Science | Single-photon coherent radiation sources. | SiV and GeV centers offer intense, narrow ZPLs and low spectral diffusion, crucial for stable quantum emitters. |
| Biomedicine & Sensing | Luminescent markers, local hyperthermia, optical temperature sensing. | Boron doping increases the absorption coefficient, enabling effective laser heating for thermoablation (hyperthermia). SiV/GeV ZPLs are highly temperature-sensitive, allowing them to function as optical temperature sensors. |
| High-Power Electronics | Electronic component base, conductive films. | Boron doping creates deep acceptor levels (0.37 eV), yielding conductive diamond films necessary for high-power devices and transparent conductive electrodes. |
| Electrochemical Processes | Corrosion-resistant photoelectrocatalysts, electrodes. | Boron-doped diamond particles (DPs) are utilized as robust, conductive electrodes and catalysts due to their chemical stability and conductivity. |
| Capacitors & Energy Storage | Materials for double electric layer capacitors. | Boron-doped nanodiamonds offer high surface area and conductivity suitable for advanced capacitor designs. |
| Doping Monitoring/Process Control | Real-time quality control during CVD growth. | The SiV ZPL intensity acts as a highly sensitive in situ indicator for monitoring the incorporation rate and concentration of boron atoms during the synthesis process. |
View Original Abstract
The effect of doping with boron on the luminescent properties of diamond particles synthesized by Hot Filament Chemical Vapor Deposition technique with color centers embedded during the growth process has been studied. It is shown that at low boron doping level, the photoluminescence intensity of a narrow zero-phonon line of the silicon-vacancy color center (738.2 nm) demonstrates a strong dependence on the concentration of boron atoms at the sites of the diamond lattice. The dependence of the intensity of a broad photoluminescence band in the wavelength range 520-800 nm on the concentration of boron atoms in the gas mixture in the range from 14 to 64000 ppm has been analyzed. The Raman scattering spectra of the obtained particles have been studied. At the concentration of boron atoms in the gas mixture up to 1540 ppm, the Raman scattering spectra of diamond particles practically do not change when the boron concentration is varied. At high boron doping level, the diamond band in the Raman spectra exhibit a spectral response typical of the Fano resonance. Keywords: diamond particles, color centers, boron doping, photoluminescence, chemical vapor deposition.