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JSD
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CVD Single crystal diamond substrate Diamond gold plated heat sink Diamond metallization
Depositing a thin film of gold (Au) on the surface of Chemical Vapor Deposition (CVD) single-crystal diamond is a critical process for material functionalization and device integration. While diamond possesses extreme physical and chemical properties (e.g., supreme hardness, highest thermal conductivity, wide bandgap, biocompatibility), the gold coating provides excellent electrical, thermal, and optical interfacial characteristics.
Electrical Contact: To fabricate low-resistance, stable ohmic or Schottky contact electrodes for diamond-based electronic devices (e.g., detectors, diodes, transistors). Gold's high electrical conductivity and chemical inertness make it an ideal choice.
Thermal Management: To serve as an efficient thermal interface material. Combining diamond's supreme bulk thermal conductivity with gold's high in-plane conductivity significantly reduces the interfacial thermal resistance between devices and heat sinks, crucial for high-power lasers, RF devices, etc.
Optical Functionalization: To act as a high-performance reflective or filter coating, especially for optical windows, laser mirrors, and biochemical sensors utilizing surface plasmon resonance (SPR) effects in the IR to UV spectrum.
Chemical Protection & Bonding: To protect the diamond surface from high-temperature oxidation or chemical corrosion. Additionally, the gold layer facilitates high-reliability packaging integration via soldering or eutectic bonding (e.g., Au-Sn).
Quantum Technology: In diamond quantum devices based on nitrogen-vacancy (NV) centers, patterned gold structures function as microwave antennas or electrodes for precise manipulation and readout of electron spin states.
Due to the high chemical inertness of diamond, direct gold deposition results in poor adhesion. A multi-layer metallization scheme is typically employed:
Surface Pretreatment: Cleaning and activating the diamond surface via acid cleaning, oxygen plasma treatment, etc.
Adhesion Layer Deposition: First, a very thin (~10-50 nm) layer of reactive metal, such as Titanium (Ti) or Chromium (Cr), is sputtered or evaporated. These metals form strong chemical bonds with carbon atoms on the diamond surface, providing anchoring.
Gold Layer Deposition: The main gold layer of desired thickness (tens of nm to several μm) is deposited atop the adhesion layer. Common methods include electron-beam evaporation, magnetron sputtering, or electroplating.
Patterning (Optional): Photolithography and etching techniques are used to pattern the continuous metal film into specific electrode or circuit geometries.
Annealing (Optional): A low-temperature anneal in an inert atmosphere may be performed to improve the contact properties at the metal-diamond interface and reduce contact resistance.
Adhesion: Ensuring the Ti/Au or Cr/Au multilayer structure does not delaminate under thermal cycling or mechanical stress is paramount. Control of interfacial reactions and roughness is critical.
High-Temperature Stability: Gold tends to diffuse into other layers at elevated temperatures, potentially compromising long-term device reliability. A diffusion barrier layer (e.g., Pt, Ni) is sometimes needed.
Interfacial Resistance: For electronic devices, optimizing the barrier height and contact resistance between the metal and doped diamond is key to performance.
Cost: Gold is a precious metal, necessitating a balance between performance and cost, often achieved through selective deposition on critical areas.
High-Power/High-Frequency Electronics: Heat spreaders and gate/drain electrodes for diamond-based GaN power amplifiers.
Particle & Radiation Detectors: Signal collection electrodes for X-ray, UV, and charged particle detectors.
Bio/Chemical Sensors: SPR sensor chips for highly sensitive detection of molecular interactions.
Quantum Information & Sensing: Microwave resonator structures in NV-center-based magnetometers and gyroscopes.
Aerospace Optical Windows: Ultra-durable, high-reflectivity protective coatings.
Size Available:
| Thermal Conductivity | ≥600 W/mK |
| Thermal Expansion Coefficient | 4.5-8 ppm/K（adjustable） |
| Density | 5.6 g/cm3 |
| Surface Modification | Chrome, Nickel |
| Transition Layer | Titanium, Platinum |
| Contact Layer | Gold, Copper |
| Crystallographic Orientation | 100 110 111 |
| Miscut for Main Face Orientation | ±3° |
| Common Product Size | 3mm×5mm×0.5mm |
| Transverse Tolerance | ±0.05mm |
| Thickness Tolerance | ±0.1mm |
| Edge Cutting | Laser Cutting |
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