Influence of CVD diamond growth conditions and misorientation angle on nitrogen incorporation

At a Glance

Metadata	Details
Publication Date	2017-01-01
Journal	EPJ Web of Conferences
Authors	M. A. Lobaev, А. М. Горбачев, С. А. Богданов, A. L. Vikharev, D.B. Radishev
Institutions	Institute of Applied Physics
Citations	2
Analysis	Full AI Review Included

6CCVD Technical Analysis: Advanced CVD Diamond Delta Doping for NV Centers

This analysis addresses the techniques and specifications required for creating high-density nitrogen-vacancy (NV) center ensembles in CVD diamond using precise delta-doping methodology, connecting research findings directly to 6CCVD’s material and engineering capabilities.

Executive Summary

This research successfully demonstrates the fabrication of ultra-thin, highly concentrated nitrogen delta layers in CVD diamond, crucial for next-generation quantum information processing (QIP) and ultra-sensitive magnetometry applications.

Precision NV Layer Fabrication: Achieved nanoscale depth control (down to 3 nm) of nitrogen incorporation through rapid gas switching in a novel MPCVD reactor.
High Dopant Density: Demonstrated peak nitrogen concentrations up to ~10¹⁹ cm^-3 within the ultra-thin delta layers.
Superior Defect Quality: Delta doping is confirmed as superior to ion implantation, as it avoids lattice defects, predicting higher spin coherence times for the resulting NV centers.
Influence of Growth Parameters: Systematically investigated how substrate temperature, methane content (CH₄ flow), and nitrogen flow (N₂) influence nitrogen incorporation efficiency (determined to be 8 × 10^-6).
Substrate Dependence: Confirmed the strong dependence of impurity incorporation on substrate orientation and misorientation angle, necessitating precise material control.
Confirmed NV Presence: Photoluminescence (PL) spectroscopy at 77 K verified the existence of both neutral (NV⁰ at 575 nm) and negatively charged (NV^- at 637 nm) NV centers.

Technical Specifications

Parameter	Value	Unit	Context
Target Application	Quantum Information Processing (QIP) / Magnetometry	N/A	Requires high-density, low-defect NV centers
Substrate Orientation	(100) & (111)	N/A	Tested orientations; (100) used for core study
Substrate Material Type	Type IIa HPHT diamond	N/A	High-quality starting material
Substrate Dimensions Used	3.5 × 3.5 × 0.5	mm³	Sample size
Peak Nitrogen Concentration	~10¹⁹	cm^-3	Achieved in the ultra-thin delta layer
Minimum Delta Layer Thickness	3	nm	Achieved by precise gas switching
Standard Growth Rate (w/o N₂)	40-100	nm/h	Slow growth regime for high quality
Nitrogen Incorporation Efficiency	8 × 10^-6	N/A	Measured metric in the growth regime
Reactor Pressure	40	Torr	Constant growth parameter
Hydrogen (H₂) Flow	950	sccm	Constant primary gas flow
Methane (CH₄) Flow Range	0.7-1.7	sccm	Varied carbon precursor
Nitrogen (N₂) Flow Range	1-8	sccm	Varied dopant concentration
Substrate Pre-treatment Etch Depth	Up to 5	µm	ICP plasma used to remove polishing damage
PL Measurement Temperature	77	K	Required for spectroscopy analysis

Key Methodologies

The experiment relied on specific material preparation and a highly controlled MPCVD process optimized for ultra-fast gas switching to enable nanometer-scale layer control.

Substrate Selection and Preparation:
- Type IIa HPHT single crystal diamonds (SCD) of (100) and (111) orientations were selected.
- Substrates were pre-treated using ICP plasma etching up to 5 µm depth to eliminate sub-surface damage introduced during mechanical polishing.
Novel CVD Reactor Operation:
- Growth was conducted in a novel MPCVD reactor designed for speed and control.
- Key features include: Rapid gas switching capability, laminar gas flow, and axial symmetric resonant mode discharge.
- Gas residence time in the reactor was approximately 5 s, enabling fast transition between doping and non-doping growth regimes.
Controlled Growth Parameters:
- Standard operating conditions were maintained at 40 Torr pressure and 950 sccm H₂ flow.
- Parameters varied included Substrate Temperature (via heater), Methane flow (0.7-1.7 sccm), and Nitrogen flow (1-8 sccm).
Delta Doping Execution:
- Multiple thin nitrogen-doped layers (1-5 nm thick) were synthesized sequentially within a single growth run by rapidly switching the N₂ flow on and off.
- Experiments were performed on single samples with varying conditions (e.g., nitrogen flow) to eliminate the influence of substrate variation.
Characterization and Calibration:
- SIMS (Time-of-Flight Secondary Ion Mass Spectrometer): Used for depth profiling to measure nitrogen concentration.
- SIMS was calibrated using an ion-implanted HPHT diamond “test” sample with a known nitrogen concentration of 10²⁰ cm^-3.
- Photoluminescence (PL) Spectroscopy: Used micro-Raman system with 514 nm laser excitation at 77 K (liquid nitrogen) to confirm the optical signatures of NV⁰ and NV^- centers.

6CCVD Solutions & Capabilities

This research highlights the absolute necessity of ultra-high-quality SCD substrates and precise CVD engineering control. 6CCVD is uniquely positioned to supply the materials required to replicate, scale, and advance this high-tech NV center research.

Applicable Materials

To achieve high-coherence NV centers and repeatable delta doping, researchers require high-purity, low-defect diamond. 6CCVD recommends:

Optical Grade Single Crystal Diamond (SCD): Required for quantum applications. 6CCVD offers high-purity SCD with extremely low background impurities (e.g., substitutional nitrogen < 5 ppb) necessary to maximize NV center creation efficiency and spin coherence times.
Precision Orientation: The study emphasizes the critical role of misorientation angle. 6CCVD supplies SCD materials with precise (100) orientation and tight control over misorientation angles as needed for reproducible doping.
Thickness Control: 6CCVD can produce SCD layers from 0.1 µm up to 500 µm, providing flexibility for the subsequent non-doped growth layers needed to separate the delta-doped regions.

Customization Potential

6CCVD addresses the engineering and dimensional challenges inherent in advanced material synthesis:

Research Requirement	6CCVD Customization Service	Value Proposition
Substrate Size (e.g., 3.5 mm × 3.5 mm)	Custom Dimensions & Laser Cutting	6CCVD provides wafers up to 125 mm (PCD) and custom-cut SCD samples to exact required geometries.
Surface Damage Removal (ICP Etching)	Ultra-Low Damage Polishing (Ra < 1 nm)	6CCVD’s advanced polishing minimizes initial surface damage (Ra < 1 nm for SCD), often reducing or eliminating the need for deep, time-consuming post-polishing ICP etching.
Multi-layer/Device Integration	Internal Metalization Capabilities	While this paper focuses on growth, future device integration (e.g., quantum magnetometers) requires contacts. 6CCVD provides in-house metalization services (Au, Pt, Pd, Ti, W, Cu).
Specialized Calibration Standards	Custom Dopant Concentrations (BDD/N)	6CCVD can manufacture custom BDD or N-doped SCD/PCD materials to serve as precise quantitative calibration standards for SIMS analysis, similar to the 10²⁰ cm^-3 implanted standard used in the paper.

Engineering Support

This research demonstrates the fine balance required between CVD parameters (pressure, temperature, gas flow ratio) and material outcomes (N incorporation efficiency, defect density).

6CCVD’s in-house PhD engineering team specializes in diamond growth science and can assist researchers replicating or extending this high-density NV center magnetometry project. We offer expert consultation on:

Optimizing substrate selection for specific NV coherence targets.
Designing multi-layer SCD structures for quantum registers and sensing arrays.
Troubleshooting growth recipes to maximize incorporation efficiency while maintaining crystal perfection.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly. We ship globally (DDU default, DDP available).

View Original Abstract

CVD diamonds with NV-centers (nitrogen vacancy centers) are now considered as the most promising solidstate media for the realization of component base for quantum information processing due to the unique properties of NV-center electronic transitions, which allow initialization and read-out of it`s spin state [1].The concentration and spin properties of NV-centers depend on nitrogen concentration and therefore it is important to understand the dependence of nitrogen incorporation in delta-layers on CVD growth conditions.In this work, delta-layers (1-5 nm thick) doped with nitrogen were obtained during CVD synthesis using the unique setup for delta doping created in IAP RAS [2].It was shown that the subsequent CVD growth with and without nitrogen addition allows obtaining a two-dimensional structure of the NV centers with a given concentration and any required depth that may be determined with an accuracy of up to 1-2 nanometers.Also the influence of substrate temperature, nitrogen flow and methane content on nitrogen incorporation was investigated by the growth of nitrogen doped layers on ( 100) and ( 111)-oriented samples.The method of delta doping in contrast to the method of ion implantation does not produce lattice defects and allows controlling the depth of the NV-center to within a few nanometers.CVD growth allows producing singlecrystal diamond of high crystalline perfection with a low content of impurities that does not vary from sample to sample.Due to the absence of lattice damage, as in the case of ion implantation, NV-centers produced by deltadoping will have better properties (e.g. higher spin coherence times).CVD diamond growth of nitrogen-doped layers was performed in the novel CVD reactor.The main features of the reactor are: 1) rapid gas switching; 2) laminar gas flow; 3) axial symmetric resonant mode -symmetric discharge; 4) slow growth of diamond (40-100 nm/h without nitrogen addition).We achieve rapid gas switching from one input gas to another by a home-made electronic switch.The residence time of our reactor is approximately 5 s.The reactor is also capable for the growth of delta-layers doped with any other impurities, such as nitrogen.It is well-known, that incorporation of impurities during CVD diamond growth is highly dependent on the substrate orientation, and could also be affected by the misorientation angle.In order to eliminate the influence of substrate, each of the experiment was performed on one sample, varying growth conditions in a one growth process, resulting in the growth of multiple thin nitrogendoped layers (see Fig. 1).Moreover, in this work we investigated the dependence of nitrogen incorporation effi-ciency on the misorientation angle using the (100)oriented sample with multiple facets polished at different misorientation angles.

Tech Support

Original Source

DOI: https://doi.org/10.1051/epjconf/201714902003