Active charge state control of single NV centres in diamond by in-plane Al-Schottky junctions
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2015-07-16 |
| Journal | Scientific Reports |
| Authors | Christoph Schreyvogel, V. M. Polyakov, Ralf Wunderlich, Jan Meijer, Christoph E. Nebel |
| Institutions | Leipzig University, Fraunhofer Institute for Applied Solid State Physics |
| Citations | 75 |
| Analysis | Full AI Review Included |
Technical Documentation and Analysis: Active Charge State Control of Single NV Centres in Diamond
Section titled âTechnical Documentation and Analysis: Active Charge State Control of Single NV Centres in DiamondâExecutive Summary
Section titled âExecutive SummaryâThis paper demonstrates a crucial step toward scalable solid-state quantum computing and sensing by achieving active, electrical control over the charge state (NV+, NV0, NV-) of single Nitrogen-Vacancy (NV) centers in diamond.
- Core Achievement: Successful, reversible switching of single NV center charge states by modulating the band bending in the hole depletion region of a planar Al-Schottky diode on H-terminated intrinsic diamond.
- Methodology: The device relies on a two-dimensional hole gas (2DHG) formed by H-termination, enabling a Schottky barrier at the Al contact edge.
- Key Results: Charge state switching from the non-fluorescent NV+ state to the fluorescent NV0 state (+15 V reverse bias) and then to the NV- state (+20 V reverse bias).
- Material Requirement: Ultra-high purity, nitrogen-free intrinsic diamond epi-layers (300 ”m) grown by Microwave Plasma-Enhanced Chemical Vapour Deposition (MWPECVD).
- Implantation Precision: Extremely shallow NV centers (8.1 nm ± 3.1 nm below the surface) are required to interact efficiently with the surface-induced electronic structure.
- Quantum Significance: This electrical control enables stabilization of the desired NV- state for electron spin applications (qubit initialization, long coherence times) and provides a pathway for a fully scalable quantum computer architecture.
- 6CCVD Value Proposition: We provide the intrinsic, high-quality Single Crystal Diamond (SCD) substrates and highly controlled thin-film deposition and metalization services necessary to engineer these planar Schottky junction devices.
Technical Specifications
Section titled âTechnical SpecificationsâThe following data points were extracted from the experimental and simulation sections of the research paper:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Substrate Type | Ib (001) | N/A | Commercial diamond plate |
| Epi-Layer Thickness | 300 | ”m | Intrinsic, N-free SCD |
| CVD Growth Temperature | 800 | °C | MWPECVD process |
| Shallow Implant Ion | 15N | N/A | Nitrogen source for NV creation |
| Implant Energy | 5 | keV | Used for shallow layer formation |
| Implant Fluence | 108 | ions/cmÂČ | Low density required for single NV addressing |
| NV Center Depth (Simulated) | 8.1 ± 3.1 | nm | Distance from H-terminated surface |
| Annealing Parameters | 800 °C for 1h | N/A | Vacuum environment for NV activation |
| Contact Metalization | Al (Schottky) and Au (Ohmic) | N/A | Dual metal contacts |
| Contact Thickness (Al/Au) | 200 | nm | Deposited via thermal evaporation |
| Barrier Height (Al on H-term. D) | 570 | meV | Schottky junction parameter |
| Required Bias for NV0 state | +15 | V | Reverse bias potential |
| Required Bias for NV- state | +20 | V | Reverse bias potential |
| Hole Sheet Density ($\sigma_h$) | 2 $\times$ 1011 | cm-2 | Two-dimensional hole gas (2DHG) density |
| Relevant Depletion Width | 1-2 | ”m | Region where NV switching occurs |
| Nitrogen Donor Level (N) | 1.7 | eV | Below Conduction Band Minimum (ECBM) |
| NV+/0 Transition Level | 1.2 | eV | Above Valence Band Maximum (EVBM) |
| NV0/- Transition Level | 2.94 | eV | Above Valence Band Maximum (EVBM) |
Key Methodologies
Section titled âKey MethodologiesâThe core steps required to realize the in-plane Al-Schottky diode on diamond for active NV charge state control:
- High-Quality SCD Growth: Homoepitaxial growth of a thick (300 ”m), intrinsic, nitrogen-free diamond epi-layer onto a Type Ib (001) substrate using an ellipsoidal shaped MWPECVD reactor (800 °C, CH4/H2 ratio 3.5%).
- Surface Preparation: Removal of the substrate by laser cutting, followed by chemical-mechanical polishing (CMP) to achieve an atomic smooth surface, and subsequent wet chemical cleaning (H2SO4+HNO3) resulting in oxygen-termination.
- NV Center Formation: Shallow ion beam implantation of 15N (5 keV, $10^8$ ions/cmÂČ) followed by high-temperature vacuum annealing (800 °C for 1 hour) to activate NV center formation.
- Surface Electronic Engineering: Hydrogen termination (H-termination) applied via pure hydrogen plasma in the MWPECVD reactor (500 °C, 1.9 kW) to form the essential two-dimensional hole accumulation layer (2DHG).
- Device Fabrication: Realization of the in-plane Schottky diode geometry using photolithography combined with thermal evaporation to deposit 200 nm thick Al (Schottky) and Au (Ohmic) contacts.
- Confocal ”PL Analysis: Measurement of Photoluminescence (PL) spectra and PL-intensity mapping using a 532 nm laser and a long working distance objective (NA=0.6, WD=7.6 mm) to monitor NV emission and charge state switching in the depletion region.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThis research validates the critical need for precision diamond material engineeringâspecifically high-purity MPCVD diamond plates combined with tightly controlled surface termination and metalization. 6CCVD (6ccvd.com) is uniquely positioned to supply and enhance the materials and processing required for replicating and advancing this quantum device architecture.
Applicable Materials
Section titled âApplicable MaterialsâThe foundation of this device is the intrinsic, nitrogen-free diamond epi-layer. 6CCVD offers materials ideal for NV center engineering:
| Application Requirement | Recommended 6CCVD Material | Key Specifications |
|---|---|---|
| High-Purity Quantum Substrate | Optical Grade SCD (Single Crystal Diamond) | Ultra-low residual nitrogen (critical for NV- coherence). Thickness control from 0.1 ”m up to 500 ”m. |
| High-Density Sensor Arrays | Engineering Grade PCD (Polycrystalline Diamond) | Available in plates/wafers up to 125mm for scaling large sensor arrays or integration into commercial devices. |
| Charge State Stabilization | Intrinsic SCD Plates (Custom Cut) | Precision (001) orientation and minimal lattice defects required for uniform band bending and reliable H-termination. |
| Dopant Source (Alternative Method) | Boron-Doped Diamond (BDD) | While this study used H-termination for hole accumulation, BDD can be supplied if p-type bulk conductivity is explored for modified junction designs. |
Customization Potential
Section titled âCustomization PotentialâThe experiment utilized a complex fabrication scheme involving precise geometry and specialized metal contacts. 6CCVD capabilities directly address these needs:
- Custom Dimensions and Cutting: The paper used 3 x 3 mmÂł plates. 6CCVD specializes in providing custom-cut SCD plates and wafers up to 125mm in size, laser-cut to tight tolerances for integration into micro-device platforms.
- Precision Thickness Control: We can grow intrinsic SCD layers exactly matching the researcherâs requirement of 300 ”m, or thinner films (down to 0.1 ”m) necessary for optimizing near-surface NV centers for photonic integration (e.g., waveguide coupling).
- Metalization Engineering: The device requires dual Al (Schottky) and Au (Ohmic) contacts. 6CCVD maintains internal metalization facilities, offering deposition of single or multi-layer stacks including Au, Pt, Pd, Ti, W, and Cu, ensuring robust electrical contacts and reproducible barrier heights.
- Surface Finish: Achieving a controlled H-termination for 2DHG formation necessitates an atomically smooth surface. We guarantee polishing to ultra-low roughness (Ra < 1 nm for SCD), essential for maximizing the quality and performance of the resultant Schottky junction.
Engineering Support
Section titled âEngineering SupportâNV charge state control is a critical technology for solid-state quantum applications, including single-spin magnetometry and quantum computing. 6CCVDâs in-house PhD-level engineering team can assist clients with:
- Material Selection: Guidance on selecting the optimal CVD diamond grade (purity, defect density, orientation) to maximize NV- charge stability and coherence time (T2).
- Process Optimization: Consultation on necessary pre-processing (CMP, surface cleaning) and subsequent surface termination (H-termination) required to reliably form the 2DHG and desired Schottky barrier.
- Device Design Consultation: Support for integrating 6CCVD materials into complex electronic architectures, including electrode placement and metalization stack design for high-fidelity switching.
Call to Action: For custom specifications or material consultation related to NV-center quantum sensing or electronic devices, visit 6ccvd.com or contact our engineering team directly. We ship globally (DDU default, DDP available).