Formation mechanism and regulation of silicon vacancy centers in polycrystalline diamond films
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2022-11-28 |
| Journal | Acta Physica Sinica |
| Authors | Junpeng Li, Zeyang Ren, Jinfeng Zhang, Han-Xue Wang, Yuan-Chen Ma |
| Institutions | Wuhu Institute of Technology, Xidian University |
| Citations | 2 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive SummaryâThis research successfully demonstrates the mechanism and effective regulation of Silicon Vacancy (SiV) color center formation in polycrystalline diamond films grown on silicon substrates using Microwave Plasma Chemical Vapor Deposition (MPCVD).
- SiV Intensity Control: Achieved effective tuning of SiV photoluminescence (PL) intensity by adjusting the ratio of nitrogen (N2) and oxygen (O2) in the growth atmosphere.
- Performance Range: The ratio of the SiV PL peak (738 nm) to the intrinsic diamond peak (572.9 nm) was varied dramatically, ranging from a maximum of 334.46 (N2-promoted growth) to a minimum of 1.48 (O2-inhibited growth).
- Nitrogen (N2) as Promoter: N2 increases the diamond film growth rate and induces preferred crystal orientation, which accelerates the diffusion of silicon from the substrate, leading to higher SiV concentration.
- Oxygen (O2) as Inhibitor: O2 suppresses diamond growth, resulting in smaller grain sizes and increased non-diamond carbon content, thereby inhibiting the secondary diffusion of Si into the crystal lattice and reducing SiV concentration.
- Formation Mechanism: SiV centers are formed via a two-stage diffusion process of elemental silicon originating from the Si substrate: 1) initial diffusion into the diamond grain during nucleation, and 2) secondary diffusion into the growing crystal structure as the grains enlarge.
- Structural Correlation: High SiV emission intensity is strongly correlated with larger diamond grain size and clear preferred crystal orientation, confirming that structural quality is key to defect incorporation.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| SiV Zero Phonon Line (ZPL) | 738 | nm | Primary emission wavelength of SiV- center. |
| Diamond Intrinsic Peak | 572.9 | nm | Used as normalization reference for PL intensity. |
| SiV/Diamond PL Ratio (Max) | 334.46 | Dimensionless | Sample S2 (0.01% N2 addition). |
| SiV/Diamond PL Ratio (Min) | 1.48 | Dimensionless | Sample S3 (0.25% O2 addition). |
| Growth Temperature | 950 | °C | Constant for all MPCVD runs. |
| Microwave Power | 4200 | W | Constant for all MPCVD runs. |
| Growth Pressure | 185 | mbar | Constant for all MPCVD runs. |
| Methane (CH4) Flow | 10 | sccm | Constant carbon source flow. |
| Maximum Growth Rate | 3.95 | ”m/h | Sample S2 (N2 promoted). |
| Minimum Growth Rate | 0.62 | ”m/h | Sample S3 (O2 inhibited). |
| Silicon Substrate | (111) | Crystal Plane | Intrinsic Si used as the source of Si dopant. |
| Diamond Raman Peak | 1332 | cm-1 | Characteristic peak of sp3 diamond lattice. |
| Silicon Raman Peak | 520.7 | cm-1 | Observed on the surface of O2-containing samples (S3, S4, S5). |
Key Methodologies
Section titled âKey MethodologiesâThe polycrystalline diamond films were synthesized using an in-house developed Microwave Plasma Chemical Vapor Deposition (MPCVD) system.
- Substrate Preparation:
- Substrates were 15 mm x 15 mm intrinsic (111) Si wafers.
- Cleaning involved 15 min ultrasonic baths in acetone, anhydrous ethanol, and deionized water, followed by N2 drying.
- Seeding was performed using a 7-8 nm nanodiamond particle suspension (15 min ultrasonic treatment).
- MPCVD Growth Conditions (2 hours duration):
- Fixed Parameters: 4200 W microwave power, 185 mbar pressure, 950 °C temperature, 10 sccm CH4 flow, 200 sccm total gas flow (H2 balance).
- Gas Composition Variation (Key Experimental Variable):
| Sample | N2 Flow (sccm) | O2 Flow (sccm) | N2 Concentration | O2 Concentration | Resulting SiV Ratio |
|---|---|---|---|---|---|
| S1 (Reference) | 0 | 0 | 0% | 0% | 57.07 |
| S2 (N2 Promoter) | 0.02 | 0 | 0.01% | 0% | 334.46 (Max) |
| S3 (O2 Inhibitor) | 0 | 0.5 | 0% | 0.25% | 1.48 (Min) |
| S4 (N2 + O2) | 0.02 | 0.5 | 0.01% | 0.25% | 37.26 |
| S5 (N2 + High O2) | 0.02 | 1.0 | 0.01% | 0.5% | 8.55 |
- Characterization Techniques:
- Thickness Measurement: Nikon MFC-101A height gauge (0.1 ”m precision).
- Morphology: ZEISS Sigma 300 Field Emission Scanning Electron Microscope (SEM).
- Optical/Defect Analysis: WITec Alpha300Rs Scanning Nearfield Optical Microscope (SNOM) for PL and Raman spectroscopy (532 nm laser, 600 grooves/mm grating).
- Spatial Mapping: PL and Raman surface scanning (10 ”m x 10 ”m area) and depth scanning were used to map SiV and Si element distribution.
Commercial Applications
Section titled âCommercial ApplicationsâThe ability to precisely control the density and location of SiV centers in polycrystalline diamond films is critical for scaling up quantum technologies and advanced bio-sensing applications.
- Quantum Information Processing: SiV centers are leading candidates for solid-state qubits due to their narrow optical linewidth and high quantum efficiency, enabling robust quantum memory and entanglement generation.
- Quantum Sensing: SiV centers, particularly when integrated into high-quality diamond films, are used for high-sensitivity measurements of temperature, strain, and magnetic fields at the nanoscale.
- Biomarkers and Bio-imaging: SiV centers emit in the near-infrared (738 nm), which is advantageous for biological applications as it minimizes light absorption and autofluorescence from biological tissues, leading to clearer signals and deeper penetration than visible-light emitters (like NV centers).
- Integrated Photonics: Controlled SiV incorporation allows for the fabrication of diamond-based integrated photonic circuits, where the emitters are precisely placed within waveguides or microcavities to enhance light-matter interaction.
- Controlled Defect Engineering: This methodology provides a reliable, scalable chemical route (via gas phase control) to manufacture diamond films with tailored quantum defect densities, moving beyond expensive and complex ion implantation techniques.
View Original Abstract
Diamond silicon vacancy centers (SiV centers) have important application prospects in quantum information technology and biomarkers. In this work, the formation mechanism and regulation method of SiV center during the growth of polycrystalline diamond on silicon substrate are studied. By changing the ratio of nitrogen content to oxygen content in the growing atmosphere of diamond, the photoluminescence intensity of SiV center can be controlled effectively, and polycrystalline diamond samples with the ratios of SiV center photoluminescence peak to diamond intrinsic peak as high as 334.46 and as low as 1.48 are prepared. It is found that nitrogen promotes the formation of SiV center in the growth process, and the inhibition of oxygen. The surface morphology and photoluminescence spectrum for each of these samples show that the photoluminescence peak intensity of SiV center is positively correlated with the grain size of diamond, and the SiV centerâs photoluminescence peak in the diamond film with obvious preferred orientation of crystal plane is higher. The distribution of Si centers and SiV centers on the surface of polycrystalline diamond are further characterized and analyzed by photoluminescence, Raman surface scanning and depth scanning spectroscopy. It is found that during the growth of polycrystalline diamond, the substrate silicon diffuses first into the diamond grain and then into the crystal structure to form the SiV center. This paper provides a theoretical basis for the development and application of SiV centers in diamond.