Влияние бора на структуру и проводимость тонких пленок, получаемых лазерной абляцией алмаза при 700-=SUP=-o-=/SUP=-C
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2018-01-01 |
| Journal | Письма в журнал технической физики |
| Authors | Р.И. Романов, В.Ю. Фоминский, Pavel V. Zinin, И.А. Троян, Д.В. Фоминский |
| Analysis | Full AI Review Included |
Technical Analysis & Documentation: Boron Doping in Laser-Ablated Diamond Films
Section titled “Technical Analysis & Documentation: Boron Doping in Laser-Ablated Diamond Films”6CCVD Ref: PJTF.2018.12.46286.17275 Research Focus: Pulsed Laser Ablation (PLA) synthesis of highly boron-doped amorphous carbon/diamond (a-C:Bx) thin films and analysis of resulting metallic conductivity and structural modification at high temperatures (700°C).
Executive Summary
Section titled “Executive Summary”- Core Achievement: Successful synthesis of ultra-low resistivity, highly boron-doped carbon films (C:Bx) using Pulsed Laser Ablation (PLA) of pressed diamond/boron powder targets onto substrates heated to 700°C.
- Record Resistivity: Achieved a record low specific resistance of 1.4 mΩ * cm at 300 K for diamond-like B-containing films, with metallic conduction confirmed by a further decrease to 0.2 mΩ * cm at 77 K.
- High Doping Efficiency: The chosen synthesis conditions resulted in highly efficient boron incorporation, achieving resulting atomic concentrations up to $x \approx 0.6$ (C:B0.6), significantly exceeding the B/C ratio of the target (0.33).
- Structural Impact: High substrate temperature (700°C) promoted effective B/C mixing and diffusion, suppressing the formation of laminar-packed graphite $sp^{2}$ clusters typically observed in similar a-C films.
- Structure vs. Conductivity: Films maintained a high concentration of $sp^{3}$ bonds (~80%) while exhibiting metallic conductivity, demonstrating potential for expanding the practical application range of B-doped diamond films.
- Methodology: PLA utilized a Nd:YAG laser (266 nm, 7 J/cm²) to ablate targets made from micron-sized diamond and boron powder mixtures.
Technical Specifications
Section titled “Technical Specifications”| Parameter | Value | Unit | Context |
|---|---|---|---|
| Synthesis Method | Pulsed Laser Ablation (PLA) / ИЛО | N/A | Films deposited on heated substrates (NaCl or Si) |
| Substrate Temperature ($T_{sub}$) | 700 | °C | Essential for promoting B/C diffusion and structure control |
| Deposition Pressure | ~ 10⁻³ | Pa | Vacuum chamber environment |
| Laser Wavelength | 266 | nm | Fourth harmonic of Nd:YAG laser |
| Laser Energy Density | ~ 7 | J/cm² | Applied to the ablation target area |
| Target B/C Atomic Ratio | 0.33 | N/A | Starting ratio of the pressed diamond/boron powder target (C:B0.33) |
| Resulting Film B Content ($x$) | 0.4 to 0.6 | N/A | Actual resulting concentration (C:Bx) |
| Film Thickness (Thick Films) | ~ 90 | nm | Measured by cross-sectional SEM (30 min deposition) |
| $sp^{3}$ Bond Concentration | 0.8 (80) | N/A (%) | High concentration, measured by EELS (vs. 0.7 for pure a-C) |
| Resistivity (300 K) | ~ 1.4 | mΩ * cm | Record low resistivity for this material type |
| Resistivity (77 K) | ~ 0.2 | mΩ * cm | Demonstrates metallic conductivity (resistance decreases with T) |
| Reported Superconductivity ($T_{c}$) | 4 - 55 | K | Referenced literature values for B-doped diamond films |
Key Methodologies
Section titled “Key Methodologies”The synthesis and characterization of the highly doped C:Bx films relied on precise control of the target composition and deposition environment, coupled with advanced surface analysis techniques.
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Target Preparation:
- Targets were fabricated by pressing a mixture of diamond powder (up to 1 µm, 75%) and boron powder (up to 5 µm, 25%).
- The resulting atomic ratio was $B/C = 0.33$ (C:B0.33).
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Pulsed Laser Ablation (PLA):
- A Nd:YAG laser (fourth harmonic, 266 nm) was used for ablation.
- Laser pulse energy was 40 mJ, resulting in an energy density of 7 J/cm² at the target surface.
- Deposition was performed in a vacuum chamber at a pressure of $\approx 10^{-3}$ Pa.
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Deposition Conditions:
- The films were deposited onto substrates (NaCl crystals for structural study; Si wafers for electrical study) heated to a high temperature ($T_{sub} = 700^{\circ}$C).
- Deposition times ranged from 2.5 minutes (thin films) to 30 minutes (thick films, $\approx 90$ nm).
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Structural and Compositional Analysis:
- Composition was verified using Energy-Dispersive X-ray Spectroscopy (EDS/ЭРС).
- Structure, specifically the $sp^{2}/sp^{3}$ ratio, was analyzed using Electron Energy Loss Spectroscopy (EELS/ХПЭЭ). EELS confirmed a high $sp^{3}$ content of $\approx 80%$.
- Microstructure (amorphous nature) was studied via Transmission Electron Microscopy (TEM/ПЭМ) and Microdiffraction (МД).
- Chemical bonding states (C-B, C-O, sp², sp³) were analyzed by X-ray Photoelectron Spectroscopy (XPS/РФЭС) after ion cleaning.
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Electrical Measurement:
- Specific resistance was measured using the Van der Pauw method on films deposited on Si substrates.
- Measurements were conducted across a temperature range (300 K down to 77 K) to confirm the metallic conduction type.
6CCVD Solutions & Capabilities
Section titled “6CCVD Solutions & Capabilities”The research demonstrates the potential of highly boron-doped carbon films for advanced electronic and superconducting applications, specifically achieving metallic conductivity through extreme B-doping and temperature-assisted structural control. While the paper uses Pulsed Laser Ablation (PLA), 6CCVD is an expert in industrial-scale Microwave Plasma Chemical Vapor Deposition (MPCVD) BDD, which provides scalable, high-purity alternatives to replicate and extend this research.
Applicable Materials & Components
Section titled “Applicable Materials & Components”To replicate this work (e.g., supplying targets for PLA) or to transition this material capability into scalable device fabrication via MPCVD, 6CCVD offers the following expert solutions:
| Material Grade | Description & Application | 6CCVD Capability Match |
|---|---|---|
| Heavy Boron-Doped PCD | Used for conductive substrates, electrodes, and potentially as high-density PLA targets (up to 125 mm diameter). Our PCD is highly conductive and scalable. | Thickness: 0.1 µm - 500 µm |
| Heavy Boron-Doped SCD (Single Crystal) | Required for high-precision, low-defect $sp^{3}$-rich electrodes or substrates demanding superior thermal management and crystal quality, potentially yielding even higher $T_{c}$ than amorphous films. | Polishing: Ra < 1 nm (SCD) |
| Custom PLA Targets | We can supply high-purity, custom-sized MPCVD-grown PCD or SCD diamond targets for customers who prefer to continue optimizing the PLA method described in the paper. | Custom Dimensions: Plates/wafers up to 125 mm |
Customization Potential for Research Replication
Section titled “Customization Potential for Research Replication”The paper utilizes specific dimensions and requires precise electrical characterization, areas where 6CCVD excels:
- Thin Film Control: The research achieved film thicknesses of $\approx 90$ nm. 6CCVD specializes in ultra-thin SCD and PCD films starting at 0.1 µm (100 nm), allowing precise control for scaling or modifying the deposition recipe.
- Ablation Targets: If the research requires specialized B-doped diamond targets (e.g., custom B concentration or specific surface finish for improved ablation quality), 6CCVD offers full customization.
- Metalization Services: To utilize the record-low resistivity in actual devices, highly reliable electrical contacts are necessary. 6CCVD provides in-house metalization capabilities, including Au, Pt, Pd, Ti, W, and Cu stacks, essential for stable Van der Pauw measurements and device integration.
- Large Area Scaling: While PLA is excellent for research, 6CCVD’s MPCVD capabilities allow scaling of conductive BDD films to large areas (up to 125 mm PCD) for commercial device production.
Engineering Support
Section titled “Engineering Support”The challenges described—achieving ultra-high B-doping while suppressing $sp^{2}$ (graphitic) clusters—are central to advanced diamond material science. 6CCVD’s in-house PhD team has extensive experience in controlling boron incorporation and optimizing crystallinity/conductivity trade-offs using MPCVD. We can assist researchers and engineers with material selection and custom parameter development for similar highly conductive diamond or superconducting diamond projects.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly. Global shipping (DDU default, DDP available) ensures rapid delivery of critical components worldwide.
View Original Abstract
AbstractStructural features of CB_ x films obtained by pulsed laser ablation of targets made of pressed diamond powder with boron-powder additions at B/C atomic ratio of x = 0.33 have been studied. The films were deposited on heated substrates, so that diffusion processes involving C and B atoms on the surface and in the volume of films were possible. Selected conditions of film deposition ensured their effective doping with boron (0.4 ≤ x ≤ 0.6). The incorporation of B atoms was accompanied by the formation of B-C chemical bonds, whereas the formation of sp ^2 graphite bonds and their ordering in clusters with laminar packing was suppressed. The films possessed very low resistivity (~1.4 mΩ cm) at room temperature and exhibited metallic type of conductance on decreasing the temperature to 77 K.