TEM study of defects versus growth orientations in heavily boron‐doped diamond
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2015-06-18 |
| Journal | physica status solidi (a) |
| Authors | Fernando Lloret, D. Araújo, M. P. Alegre, J.M. González-Leal, M.P. Villar |
| Institutions | Centre National de la Recherche Scientifique, Universidad de Cádiz |
| Citations | 17 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Heavily Boron-Doped Diamond Defects
Section titled “Technical Documentation & Analysis: Heavily Boron-Doped Diamond Defects”Executive Summary
Section titled “Executive Summary”This analysis summarizes a Transmission Electron Microscopy (TEM) study on extended defects in heavily boron-doped diamond (BDD) grown by Microwave Plasma Chemical Vapor Deposition (MPCVD). The findings are crucial for optimizing BDD material quality for high-power electronic devices, a core focus area for 6CCVD.
- Core Mechanism Confirmed: Extended defects (dislocations and stacking faults) are generated primarily due to local in-plane strain induced by neighboring boron atom pairs, rather than traditional lattice mismatch at layer interfaces.
- Orientation Dependence: Defect generation exhibits a strong dependence on growth orientation. A high density of dislocations was observed in the <111> family planes, while the standard <100> growth direction remained largely defect-free under identical conditions.
- Material Structure: The study utilized a stack of nine undoped and heavily boron-doped (p++) diamond bilayers grown homoepitaxially on a <100> polished CVD diamond substrate.
- Defect Identification: TEM and HREM confirmed the presence of threading edge dislocations with Burger vectors of 1/6 [112] and 1/2 [110], and Stacking Faults (SFs) corresponding to the Σ3 {111} Coincident-Site-Lattice (CSL) structure.
- Technological Relevance: The results provide essential guidance for engineers seeking to minimize defects in BDD films by strictly controlling growth orientation, a critical step for developing reliable commercial electronic devices.
Technical Specifications
Section titled “Technical Specifications”The following hard data points were extracted from the MPCVD growth conditions used to produce the heavily boron-doped diamond bilayers:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Substrate Orientation | <100> | Crystal Plane | Polished CVD diamond substrate |
| Substrate Size | 3 x 3 | mm2 | Sample dimensions |
| Boron Doping Concentration (p++) | 1020 | at/cm3 | Heavily doped layers |
| Substrate Temperature (Tsub) | 910 | °C | Constant for both doped and undoped growth |
| Pressure | 33 | Torr | Constant for both doped and undoped growth |
| Dopant Gas Ratio (B2H6/CH4) | 7000 | ppm | Used during p++ layer growth |
| Methane Concentration (NID Layer) | 0.75 | % | Non-intentionally doped (NID) layer |
| Methane Concentration (p++ Layer) | 0.5 | % | Heavily doped layer |
| Oxygen Concentration (NID Layer) | 0.32 | % | O2/H2 ratio during NID growth |
| Flow Rate (Total) | 200 | sccm | Constant for both growth types |
| H2 Flush Duration | 10 | sec | Used between layer transitions |
| Identified Burger Vectors (A) | 1/6 [112] | N/A | Threading dislocations |
| Identified Burger Vectors (B) | 1/2 [110] | N/A | Threading dislocations |
Key Methodologies
Section titled “Key Methodologies”The heavily boron-doped diamond multilayer structure was grown using Microwave Plasma Chemical Vapor Deposition (MPCVD) under highly controlled, alternating conditions:
- Substrate Preparation: A 3x3 mm2, <100> oriented polished CVD diamond substrate was used. An initial 2-hour pure hydrogen plasma treatment was performed to eliminate residual contamination.
- Multilayer Design: A stack of nine bilayers, alternating between Non-Intentionally Doped (NID) and heavily boron-doped (p++) layers, was grown.
- NID Layer Growth Parameters:
- Methane concentration (CH4/H2): 0.75%.
- Oxygen addition (O2/H2): 0.32%.
- Temperature and Pressure: 910 °C and 33 Torr.
- p++ Layer Growth Parameters:
- Methane concentration (CH4/H2): 0.5%.
- Boron doping (B2H6/CH4): 7000 ppm, resulting in 1020 at/cm3 concentration.
- Temperature and Pressure: 910 °C and 33 Torr.
- Interface Control: A short (10 sec) pure hydrogen flush (2000 sccm) was performed between the growth of the NID and p++ layers to ensure sharp transitions without interrupting the plasma.
- Characterization: Cross-sectional lamellas were prepared using Focused Ion Beam (FIB) lift-out techniques. Defects were analyzed using TEM, High-Resolution TEM (HREM), and Annular Dark Field (ADF) imaging, employing the g·b invisibility criterion to determine Burger vectors.
6CCVD Solutions & Capabilities
Section titled “6CCVD Solutions & Capabilities”This research highlights the critical need for precise control over doping, growth orientation, and layer thickness—all areas where 6CCVD provides industry-leading expertise and custom manufacturing capabilities.
Applicable Materials for Replication and Extension
Section titled “Applicable Materials for Replication and Extension”To replicate or extend this research, particularly focusing on high-quality, low-defect BDD films for electronic applications, 6CCVD recommends the following materials:
- Heavy Boron-Doped Diamond (BDD): 6CCVD specializes in custom BDD films, offering precise control over doping levels up to and exceeding the 1020 at/cm3 concentration used in this study. Our BDD material is ideal for metallic diamond electrodes and active electronic layers.
- High-Quality Single Crystal Diamond (SCD) Substrates: The study utilized a <100> oriented substrate, which proved crucial for minimizing defects. 6CCVD provides high-purity, polished SCD substrates (up to 500 µm thick) with precise <100> orientation for homoepitaxial growth.
- Custom Multilayer Structures: We offer the capability to grow complex, alternating SCD/BDD multilayer stacks with layer thickness control down to 0.1 µm, ensuring the sharp interfaces required for advanced device architectures.
Customization Potential for Advanced Research
Section titled “Customization Potential for Advanced Research”6CCVD’s in-house manufacturing capabilities directly address the needs of advanced diamond research:
| Research Requirement | 6CCVD Customization Capability | Value Proposition |
|---|---|---|
| Substrate Size/Area | Plates/wafers up to 125 mm (PCD) and large-area SCD. | Enables scaling from 3x3 mm2 research samples to commercial device dimensions. |
| Thickness Control | SCD and PCD layers from 0.1 µm to 500 µm. Substrates up to 10 mm. | Allows precise control over the thickness of the doped layers and buffer layers, critical for defect management. |
| Surface Quality | Polishing capability to achieve Ra < 1 nm (SCD) and Ra < 5 nm (Inch-size PCD). | Ensures ultra-smooth surfaces necessary for high-resolution TEM/HREM analysis and subsequent device fabrication. |
| Post-Processing | Internal metalization services (Au, Pt, Pd, Ti, W, Cu). | If these BDD layers were to be used as electrodes or contacts, 6CCVD can apply custom metal stacks directly to the diamond surface. |
| Orientation Study | Provision of custom-cut substrates (e.g., <111>, <110>) to further investigate the orientation dependence of defect generation. | Supports researchers looking to extend the findings regarding defect affinity for specific crystal planes. |
Engineering Support
Section titled “Engineering Support”6CCVD’s in-house PhD team specializes in MPCVD growth recipes and material characterization. We offer comprehensive engineering support to assist researchers and engineers in:
- Material Selection: Choosing the optimal diamond type (SCD, PCD, BDD) and orientation (<100> vs. <111>) to minimize defects for specific High-Power Electronic Device applications.
- Recipe Optimization: Consulting on gas ratios (CH4/H2, B2H6/CH4) and temperature profiles to achieve target doping concentrations (e.g., 1020 at/cm3) while maintaining structural integrity.
- Global Logistics: Ensuring reliable global shipping (DDU default, DDP available) for sensitive, high-value diamond materials.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Heavy boron‐doping layer in diamond can be responsible for the generation of extended defects during the growth processes (Blank et al., Diam. Relat. Mater. 17 , 1840 (2008) ). As claimed recently (Alegre et al., Appl. Phys. Lett. 105 , 173103 (2014) ), boron pair interactions rather than strain‐related misfit seems to be responsible for such dislocation generation. In the present work, electron microscopy observations are used to study the defects induced by heavy boron doping in different growth plane orientations. Facets of pyramidal Hillocks (PHs) and pits provide access to non‐conventional growth orientations where boron atoms incorporation is different during growth. TEM analysis on FIB prepared lamellas confirm that also for those growth orientations, the generation of dislocations occurs within the heavily boron‐doped diamond layers. Stacking faults (SFs) have been also observed by high resolution transmission electron microscopy (HREM). From the invisibility criteria, using weak beam (WB) observation, and , Burgers vectors have been identified. Their generation behavior confirms the mechanism reported by Alegre et al. where local in‐plane strain effects induced at the growing surface of the diamond lattice by the neighboring of several boron atoms cause the generation of such extended defects.