Nitrogen Desorption and Positron Sensitive Defect of CVD Diamond
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2017-01-01 |
| Journal | Journal of Modern Physics |
| Authors | K. Lund, Kelvin G. Lynn, Marc H. Weber, Chao Liu, E.E. Eissler |
| Institutions | National Superconducting Cyclotron Laboratory, II-VI (United States) |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Defect Engineering in CVD Diamond
Section titled âTechnical Documentation & Analysis: Defect Engineering in CVD DiamondâThis document analyzes the research paper âNitrogen Desorption and Positron Sensitive Defect of CVD Diamondâ to provide technical specifications and demonstrate how 6CCVDâs advanced MPCVD diamond products and services are essential for replicating and advancing this critical research in quantum and detector applications.
Executive Summary
Section titled âExecutive Summaryâ- Core Achievement: Demonstrated precise control over vacancy and nitrogen-related defects (NV centers, divacancies V2) in CVD diamond through high-temperature annealing and characterized them using Doppler Broadening of Positron Annihilation Radiation (DBAR).
- Nitrogen Control: Confirmed that nitrogen impurities are liberated from CVD diamond at extremely high temperatures, specifically between 1850 K and 1900 K, correlating directly with an increase in the bulk S-parameter (defect concentration/size).
- Defect Creation: Annealing at 900 K - 1050 K promotes monovacancy migration to form NV centers, while annealing at 1410 K is used to create divacancies (V2), crucial for advanced quantum switches.
- Light Sensitivity: Identified a light-sensitive, time-dependent defect state (likely the NV center charge state) that decays in the dark (time constant 20 - 90 minutes) and is instantaneously regenerated by exposure to 470 nm light.
- Material Requirement: The study underscores the necessity of ultra-high purity CVD diamond with controlled doping and precise surface preparation (Mechanical Polish vs. RIE) for reliable defect engineering in radiation sensors and quantum computing.
- 6CCVD Value Proposition: 6CCVD provides the necessary high-purity Single Crystal Diamond (SCD) and large-area Polycrystalline Diamond (PCD) substrates, along with custom polishing and annealing optimization support, required to achieve these highly controlled defect states.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Nitrogen Desorption Temperature Range | 1850 - 1900 | K | Observed for high N content samples (A-D) |
| Monovacancy Migration Temperature | 900 - 1050 | K | Temperature range for NV center formation |
| Divacancy Creation Target Temperature | 1410 | K | Annealing temperature used to induce V2 defects |
| Annealing Hold Time | 24 | hours | Constant temperature hold for defect stabilization |
| Vacuum Base Pressure (Heating) | 5 x 10-9 | Torr | Ultra-high vacuum environment |
| Positron Beam Energy (Max) | 70 | keV | Used for variable energy DBAR profiling |
| Positron Mean Implantation Depth (Max) | 10.18 | ”m | Achieved at 70 keV |
| DBAR S-parameter Decay Time Constant | 20 - 90 | min | Time constant for defect state decay in the dark |
| Light Regeneration Wavelength | 470 | nm | Blue LED used to restore S-parameter |
| Bulk S Value (GE Single Crystal Reference) | 0.40662 ± 0.0001 | Unitless | Normalization standard for defect concentration |
| N2 Released (Sample A) | 3.11 ± 0.56 | Moles x 10-9 | Detector Grade sample |
Key Methodologies
Section titled âKey MethodologiesâThe experiment utilized high-temperature annealing combined with Positron Annihilation Spectroscopy (DBAR) and Photoluminescence (PL) to characterize defect evolution in CVD diamond.
- Sample Selection and Preparation: Eight polycrystalline CVD diamond samples (Detector Grade and Optical Grade) were sourced, featuring two distinct surface finishes: Mechanical Polish and Reactive Ion Etching (RIE).
- High-Vacuum Annealing: Samples were mounted on a tantalum holder in an ultra-high vacuum system (base pressure 5 x 10-9 Torr) and heated using an electron-gun (e-gun) biased with positive high voltage.
- Temperature Profiling: Temperatures were precisely controlled and measured using optical fiber pyrometers (Sekidenko for 650 K - 1400 K, IRCON for > 1400 K). Heating profiles were designed to target specific defect migration temperatures (950 K, 1050 K, 1410 K).
- Nitrogen Desorption Measurement: A Residual Gas Analyzer (RGA 100) monitored the partial pressure of expelled gases (specifically mass 14 for N2) to determine the temperature range (1850 K - 1900 K) required for nitrogen liberation.
- Defect Analysis (DBAR): Doppler Broadening of Positron Annihilation Radiation (DBAR) was performed at room temperature before and after each annealing step to generate defect profiles (S and W parameters) from the surface to the bulk (up to 10.18 ”m depth).
- Light Sensitivity Testing: Samples were exposed to a positron beam in the dark, and the decay of the S-parameter was measured. Subsequent illumination with a 470 nm LED was used to observe the instantaneous regeneration of the defect state.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThis research demonstrates the critical need for highly controlled CVD diamond materials to advance quantum sensing and radiation detection technologies. 6CCVD is uniquely positioned to supply the necessary materials and engineering support for replicating and extending these defect engineering studies.
| Research Requirement | 6CCVD Solution & Capability | Technical Advantage |
|---|---|---|
| High-Purity Base Material (Required for controlled NV and V2 defect creation) | Optical Grade Single Crystal Diamond (SCD) | Provides the lowest initial defect density and highest purity (Type IIa), ensuring that introduced defects are precisely controlled, maximizing coherence time for quantum applications. |
| Large-Area Detector Substrates (Polycrystalline samples used for scaling) | Polycrystalline Diamond (PCD) Wafers | Available in custom dimensions up to 125mm, enabling the development of large-scale radiation detectors and sensor arrays. |
| Precise Defect Engineering (Targeting NV and V2 formation via annealing) | Custom Growth and Annealing Optimization | 6CCVD can supply substrates optimized for specific defect creation (e.g., controlled low-level nitrogen incorporation) or pre-annealed to stabilize monovacancy or divacancy populations. |
| Surface Finish for Detectors (Mechanical Polish and RIE used) | Ultra-Smooth Polishing Services | SCD polishing to Ra < 1nm and inch-size PCD polishing to Ra < 5nm, critical for minimizing surface defects that interfere with charge collection and positron implantation profiles. |
| Electrical Contact Integration (Required for detector applications) | In-House Custom Metalization | We offer internal deposition of standard and custom metal stacks (Au, Pt, Pd, Ti, W, Cu) for creating reliable ohmic contacts necessary for radiation detector prototypes. |
| Thick Substrates for Deep Probing (Positron depth up to 10.18 ”m) | Thick SCD and PCD Plates | SCD and PCD plates available up to 500 ”m thick, and substrates up to 10mm, supporting high-energy beam experiments and robust detector fabrication. |
Engineering Support
Section titled âEngineering Supportâ6CCVDâs in-house PhD team specializes in MPCVD growth and post-processing techniques, including high-temperature annealing and controlled doping. We can assist researchers in selecting the optimal material grade (e.g., Low-Nitrogen PCD or High-Purity SCD) and developing specific annealing recipes to maximize the yield and stability of light-sensitive defects for similar quantum sensing and radiation detection projects.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
The chemical vapor deposition (CVD) process can produce single or poly-crystalline diamond samples of high purity or with controlled doping concentrations. The defect type in the CVD diamonds can be changed by heating the samples. Controlling the defect type can be used to create devices for quantum diamond switches that could be used in radiation sensors and quantum information technology. Eight samples of CVD diamonds were analyzed with Doppler broadening of positron annihilation radiation (DBAR) before and after annealing in high vacuum with an electron gun. Between temperatures of 1700 - 1850 K, nitrogen was liberated from the diamond sample. At these high temperatures, the surface was graphitized and a change in the color and transparency of the diamond was observed. Some of the samples were analyzed with DBAR during periods with and without light. The defect properties were observed to change depending on the time exposure to the positron beam and were then regenerated by exposure to light. The DBAR data is compared to photoluminescence data and a time varying defect state is discussed for detector and optical grade type II CVD diamonds.