Pick-up and drop transfer of diamond nanosheets
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2015-03-05 |
| Journal | Nanotechnology |
| Authors | V. Seshan, J O Island, R. van Leeuwen, W J Venstra, B. H. Schneider |
| Citations | 9 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Ultra-Thin MPCVD Diamond Nanosheets for Advanced Device Integration
Section titled âTechnical Documentation & Analysis: Ultra-Thin MPCVD Diamond Nanosheets for Advanced Device IntegrationâReference Paper: V Seshan et al., âPick-up and drop transfer of diamond nanosheets.â Nanotechnology 26(12) 125706 (2015).
Executive Summary
Section titled âExecutive SummaryâThis research validates a critical, all-dry transfer technique for integrating ultra-thin Nanocrystalline Diamond (NCD) and Boron-Doped NCD (B-NCD) films into complex micro- and nano-devices, directly addressing major fabrication challenges in NEMS and advanced electronics.
- Material Achievement: Successful MPCVD growth and subsequent thinning of NCD nanosheets down to 55 nm thickness.
- Process Innovation: Demonstrated an all-dry, visco-elastic stamp âpick-up and dropâ transfer method, eliminating the need for harsh lithography or wet chemical etching for final device integration.
- Electronic Performance: Transferred B-NCD films exhibited a room-temperature resistivity of 6.0 Ω-cm, suitable for electronic circuits and potential superconducting applications (Tc = 2.1 K reported for highly doped films).
- Mechanical Performance: Fabricated freely suspended NCD drumhead resonators exhibiting high resonance frequencies (5 to 20 MHz) and Quality Factors (40-155), confirming plate-like mechanical behavior (Youngâs Modulus E â 300 GPa).
- Versatile Integration: Demonstrated transfer onto diverse substrates, including pre-patterned metal electrodes, optical fibers (for optical components), and 2D materials (MoS2) for complex heterostructure fabrication.
- 6CCVD Value Proposition: 6CCVD specializes in providing the high-quality, large-area, and custom-doped PCD/BDD source material required to scale this transfer technique for commercial and high-volume research applications.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the experimental results and material characterization:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| NCD Film Thickness (Initial) | ~180 | nm | Grown via MPCVD on Quartz |
| NCD Film Thickness (Thinned) | ~55 | nm | Achieved via O2 RIE |
| Youngâs Modulus (ENCD) | 300 ± 100 | GPa | Polycrystalline Diamond (Calculated) |
| Mass Density (Ï) | 3500 | kg m-3 | Polycrystalline Diamond (Typical) |
| B/C Concentration Ratio (Doping) | ~3000 | ppm | Trimethylboron gas used for B-NCD |
| B-NCD Resistivity | 6.0 | Ω-cm | Two-terminal measurement (Room Temp) |
| Resonator Frequency Range (fo) | 5 to 20 | MHz | Dependent on thickness (t) and diameter (d) |
| Resonator Quality Factor (Q) | 40 to 155 | - | Measured in vacuum (~10-5 mbar) |
| Optical Transmittance | ~60 | % | At 750 nm (for ~185 nm film) |
| RIE Etch Rate (O2) | ~15 | nm/min | Used to thin NCD nanosheets |
| Electrode Metalization Stack | 5 nm Ti / 50 nm Au | - | Pre-patterned on Si/SiO2 substrate |
Key Methodologies
Section titled âKey MethodologiesâThe NCD nanosheets were fabricated using a multi-step process combining MPCVD growth, stress-induced delamination, and dry etching.
- Substrate Preparation: Quartz substrates were seeded with diamond nanoparticles prior to growth.
- MPCVD Growth Parameters: NCD films were deposited using a conventional Microwave Plasma-Enhanced Chemical Vapour Deposition (MPCVD) process:
- Plasma Gas: H2/CH4 mixture.
- Methane Concentration: ~4 % (v/v).
- Microwave Power: 3500 W.
- Substrate Temperature: 510-560 °C.
- Process Pressure: 33-40 mbar.
- Boron Doping: For B-NCD films, Trimethylboron gas was introduced, achieving a Boron-to-Carbon concentration ratio of ~3000 ppm.
- Stress-Induced Delamination: Growth was stopped when the film reached ~180 nm. The thermal expansion mismatch between the NCD film and the quartz substrate created sufficient stress to crack and delaminate the film, forming weakly adhered nanosheets (typically 50 ”m x 50 ”m).
- Nanosheet Thinning: An all-dry Oxygen (O2) Reactive Ion Etching (RIE) process was used to reduce the thickness from ~185 nm to ~55 nm.
- RIE Parameters: DC bias ~-413 V, O2 gas flow 30 ml/min, Pressure ~20.7 ”bar.
- Transfer Technique: An all-dry pick-up and drop method utilizing a transparent visco-elastic stamp (GelFilmÂź) mounted on a 3-axis micromanipulator was used for sub-micron precision placement onto target substrates (e.g., pre-patterned SiO2, optical fibers, MoS2).
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe successful fabrication of ultra-thin, high-performance NCD and B-NCD devices relies entirely on the quality and customizability of the source material. 6CCVD is uniquely positioned to supply the necessary MPCVD diamond films to replicate and advance this research.
Applicable Materials for Replication and Extension
Section titled âApplicable Materials for Replication and Extensionâ| Research Requirement | 6CCVD Material Solution | Key Capability Match |
|---|---|---|
| Ultra-Thin NCD Films (55 nm - 185 nm) | Nanocrystalline PCD | 6CCVD offers PCD films with thickness control from 0.1 ”m (100 nm) up to 500 ”m, meeting the required thinness range. |
| Boron Doping (3000 ppm B/C) | Heavy Boron-Doped PCD (BDD) | Custom doping levels are standard. We can precisely control the B/C ratio to achieve specific resistivity (6.0 Ω-cm) or superconducting properties (Tc). |
| Large Source Material | PCD Wafers up to 125 mm | While the paper used small flakes, 6CCVD provides large-area PCD plates (up to 125 mm diameter) for scalable, high-throughput transfer processes. |
| High-Quality Mechanical Films | Polished PCD | Our polishing capability (Ra < 5 nm for inch-size PCD) ensures minimal surface roughness, critical for maximizing Q-factors in NEMS resonators. |
Customization Potential for Advanced Integration
Section titled âCustomization Potential for Advanced IntegrationâThe pick-up and drop technique is ideal for integrating diamond into complex, pre-fabricated circuits. 6CCVD supports the necessary material preparation steps:
- Custom Dimensions: We provide diamond plates and wafers up to 125 mm in diameter. We offer in-house laser cutting and dicing services to produce custom-sized source substrates optimized for specific transfer processes.
- Advanced Metalization: The paper utilized Ti/Au electrodes. 6CCVD offers internal metalization services, allowing researchers to specify complex electrode stacks (Au, Pt, Pd, Ti, W, Cu) directly deposited onto the diamond film or the source substrate, facilitating subsequent lift-off or transfer steps.
- Substrate Flexibility: We can grow NCD/PCD films on various non-diamond substrates (e.g., silicon, quartz, sapphire) to optimize the stress-induced delamination process demonstrated in this research.
Engineering Support
Section titled âEngineering SupportâThe successful integration of diamond nanosheets into applications like high-frequency NEMS resonators (5-20 MHz) and electronic heterostructures requires precise control over material properties (Youngâs Modulus, doping concentration, thickness uniformity).
6CCVDâs in-house PhD team specializes in tailoring MPCVD growth recipes (including H2/CH4 ratios, power, and temperature) to meet the exact mechanical and electrical specifications required for similar Nanomechanical Resonator and 2D Heterostructure projects. We offer consultation on optimizing doping profiles to achieve specific resistivity targets or enhance superconducting performance.
Call to Action: For custom specifications, material consultation, or to order large-area PCD source wafers for scalable transfer techniques, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Nanocrystalline diamond (NCD) is a promising material for electronic and mechanical micro- and nanodevices. Here we introduce a versatile pick-up and drop technique that makes it possible to investigate the electrical, optical and mechanical properties of as-grown NCD films. Using this technique, NCD nanosheets, as thin as 55 nm, can be picked-up from a growth substrate and positioned on another substrate. As a proof of concept, electronic devices and mechanical resonators are fabricated and their properties are characterized. In addition, the versatility of the method is further explored by transferring NCD nanosheets onto an optical fiber, which allows measuring its optical absorption. Finally, we show that NCD nanosheets can also be transferred onto two-dimensional crystals, such as MoS2, to fabricate heterostructures. Pick-up and drop transfer enables the fabrication of a variety of NCD-based devices without requiring lithography or wet processing.