Diamond films obtained on silicone substrates by the CVD method and properties of structures based on them
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2023-06-01 |
| Journal | Physical Sciences and Technology |
| Authors | Đ. ĐĄ. ĐĄĐ°ĐžĐŽĐŸĐČ, Sh. N. Usmonov, Sh. N. Usmonov, U. Kh. Rakhmonov |
| Institutions | Academy of Sciences Republic of Uzbekistan |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: MPCVD Diamond Films for Optoelectronics and Space Applications
Section titled âTechnical Documentation & Analysis: MPCVD Diamond Films for Optoelectronics and Space ApplicationsâThis document analyzes the research paper âDiamond films obtained on silicone substrates by the CVD method and properties of structures based on themâ and outlines how 6CCVDâs advanced MPCVD diamond materials and customization capabilities can support and extend this research, particularly in the fields of photovoltaics and high-performance heterojunction devices.
Executive Summary
Section titled âExecutive Summaryâ- Heterostructure Achievement: Successful fabrication of an nSi - p(15R-SiC)${1-x}$(C${diamond}$)$_{x}$ heterojunction using CVD on n-type Si (111) substrates.
- Interface Control: Confirmation via Raman spectroscopy of a critical 15R-SiC transition buffer layer formed between the silicon substrate and the polycrystalline diamond (PCD) film.
- Electrical Performance: Grown films exhibited stable p-type conductivity with high charge carrier mobility (up to 1010 cm$^{2}$/(V·s)) and carrier concentrations in the 10$^{17}$ cm$^{-3}$ range.
- Optoelectronic Functionality: Demonstrated electroluminescence (whitish-blue glow) under reverse bias breakdown (~14-15 V), confirming potential for light-emitting devices.
- Space Application Value: The diamond layer functions as a protective, conductive âwindowâ that converts high-energy, short-wavelength photons (prevalent in space) into longer-wavelength photons efficiently absorbed by the underlying silicon layer, enhancing solar cell efficiency and radiation hardness.
- Methodology: Films were grown using a hot-filament CVD technique utilizing a hydrogen-methanol mixture with ammonia (NH$_{3}$) addition for attempted nitrogen doping.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the experimental results and process parameters:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Substrate Material | Single-crystal Si (n-type) | N/A | (111) orientation |
| Substrate Resistivity | ~10 | Ω cm | Starting material |
| Substrate Dimensions | 10 x 10 x 0.3 | mm | Lab-scale wafer size |
| Film Morphology | Polycrystalline | N/A | Fine-grained, faceted crystals |
| Crystallite Grain Size | 2-3 | ”m | Individual single crystals |
| Conductivity Type (Film) | p-type | N/A | Resulting from growth/doping attempt |
| Carrier Concentration | (2-4)·10$^{17}$ | cm-3 | Measured via Hall method |
| Electron Mobility | 950-1010 | cm2/(V·s) | Measured via Hall method |
| Reverse Breakdown Voltage | ~14-15 | V | Electroluminescence onset |
| Average Growth Rate | 0.2-0.3 | ”m/h | CVD process result |
| Growth Temperature (Substrate) | 850-900 | °C | CVD process parameter |
| Growth Temperature (Filament) | 2100-2150 | °C | Tungsten filament temperature |
| Reactor Pressure | 50-60 | Torr | CVD process parameter |
Key Methodologies
Section titled âKey MethodologiesâThe diamond films were obtained using a Chemical Vapor Deposition (CVD) method, likely Hot Filament CVD, with the following key steps and parameters:
- Substrate Selection: n-type single-crystal silicon wafers (10x10x0.3 mm) with (111) orientation and ~10 Ω cm specific resistance were used.
- Surface Pre-treatment (Hydrogen Etching):
- Purpose: To clean the surface of SiO$_{2}$ and create dangling Si bonds for subsequent SiC nucleation.
- Filament Temperature: 1800°C.
- Duration: 3 min.
- Hydrogen Flow Rate: 1000 cm$^{3}$/min.
- CVD Growth Recipe:
- Gas Mixture: Hydrogen (H${2}$), Methanol (CH${3}$OH), and Ammonia (NH$_{3}$) (for N doping).
- Total Gas Flow: 50-60 cm$^{3}$/min.
- H$_{2}$/Methanol Ratio: 0.5-1.0%.
- Methanol Bubbler Temperature: 33-35°C.
- Structural Analysis: The formation of the 15R-SiC transition layer and the polycrystalline diamond structure was confirmed using Raman scattering spectroscopy (514 nm laser, 300 K).
- Electrical Characterization: Hall measurements were used to determine carrier concentration and electron mobility, confirming the resulting p-type conductivity.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & Capabilitiesâ6CCVD is uniquely positioned to supply the high-quality MPCVD diamond materials necessary to replicate, optimize, and scale the nSi-pDiamond heterostructures demonstrated in this research for advanced optoelectronic and space applications.
Applicable Materials
Section titled âApplicable Materialsâ| Research Requirement | 6CCVD Material Recommendation | Rationale |
|---|---|---|
| Polycrystalline Diamond (PCD) Film | Optical Grade PCD Wafers | Provides the necessary wide bandgap, high thermal conductivity, and radiation hardness required for protective solar cell windows. |
| Controlled p-type Layer | Boron-Doped Diamond (BDD) | The paperâs attempt at N-doping resulted in unintentional p-type material. 6CCVD offers precise, controlled Boron doping (BDD) to achieve stable, reproducible p-type conductivity (up to 10$^{21}$ cm-3). |
| High-Purity Material | High-Purity SCD or PCD | Essential for minimizing defect centers that cause unwanted recombination, ensuring efficient photon conversion and electroluminescence. |
Customization Potential
Section titled âCustomization PotentialâThe successful implementation of this technology relies heavily on material quality, interface engineering, and scalabilityâall core strengths of 6CCVD.
- Large-Scale Substrates: While the paper used small 10x10 mm samples, 6CCVD offers PCD plates/wafers up to 125 mm in diameter, enabling immediate scale-up for commercial or large-area space photovoltaic applications.
- Precision Thickness Control: The application requires thin films for transparency and conductivity. 6CCVD provides PCD films with thickness control from 0.1 ”m to 500 ”m, perfectly suited for optimizing the active layer thickness.
- Interface Optimization: The formation of the 15R-SiC buffer layer is critical. 6CCVDâs expertise in MPCVD recipe tuning (gas flow, pressure, temperature profiles) allows for custom interface engineering to control the SiC polytype and thickness, maximizing charge separation efficiency.
- Advanced Polishing: For optical and device applications, surface roughness is paramount. 6CCVD provides polishing services for inch-size PCD to Ra < 5 nm, ensuring minimal light scattering and high-quality interfaces for subsequent processing.
- Device Integration & Metalization: For creating functional devices (like the nSi-pDiamond junction), reliable contacts are needed. 6CCVD offers in-house custom metalization using materials such as Au, Pt, Pd, Ti, W, and Cu, providing a complete solution from raw material to device-ready wafer.
Engineering Support
Section titled âEngineering Supportâ6CCVDâs in-house PhD team specializes in optimizing diamond material properties for extreme environments and quantum applications. We can assist researchers and engineers with:
- Material Selection: Guidance on selecting the optimal diamond grade (SCD vs. PCD) and doping level (BDD) for high-radiation, high-temperature space applications.
- Doping Strategy: Developing recipes for controlled p-type (Boron) or n-type (Phosphorus/Nitrogen) doping to achieve specific carrier concentrations and mobilities, moving beyond the unintentional doping observed in the paper.
- Heterojunction Design: Consultation on optimizing CVD parameters to control the formation and properties of transition layers, such as the 15R-SiC buffer, critical for high-efficiency solar cells and detectors.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
At present, the technology of obtaining diamond films on silicon and other substrates is well studied. However, in all published works to date, there has been no report of a layer of silicon carbide formed between the diamond film and the silicon substrate. The presence of a layer (15R-SiХ)1-x(Cdiamond)x in the structure was revealed in the studies of structures with a diamond film obtained by us on silicon substrates by chemical vapor deposition. Diamond films were obtained on single-crystal silicon substrates with (111) orientation and n-type conductivity by the well-known CVD technology in a hydrogen-methanol (CH3OH) mixture with the addition of a certain amount (know-how) of ammonia (NH3). The diamond films consisted of small single crystals 3-5 ”m in size, closely interlocked and constituting a continuous film. When studying the current-voltage characteristics of structures created on the basis of the obtained diamond films, a blue-white glow with a blue-violet tint was observed, which is explained by the mixing of blue-violet photons with photons re-emitted in the diamond film.