Effects of metal layers on chemical vapor deposition of diamond films
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2022-09-01 |
| Journal | Journal of Electrical Engineering |
| Authors | Tibor IzsĂĄk, G. Vanko, Oleg BabÄenko, BohumĂr ZaĆ„ko, Alexander Kromka |
| Institutions | Czech Academy of Sciences, Institute of Physics, Institute of Chemistry of the Slovak Academy of Sciences |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Effects of Metal Layers on CVD Diamond Films
Section titled âTechnical Documentation & Analysis: Effects of Metal Layers on CVD Diamond FilmsâThis document analyzes the research concerning the integration of thin metal layers (Ni, Ir, Au/Ir) within MPCVD diamond structures for advanced radiation detector applications. It highlights how 6CCVDâs specialized capabilities in custom diamond growth and metalization directly address the challenges and requirements identified in the study.
Executive Summary
Section titled âExecutive Summaryâ- Application Focus: Development of robust diamond-metal heterosystems for advanced radiation detectors utilizing immersed 3D electrodes (hybrid diamond/metal/diamond composites).
- Material Compatibility: The study investigated the compatibility of Ni, Ir, and Au/Ir thin films (15-30 nm) with Microwave Plasma Chemical Vapor Deposition (MWCVD) processes.
- Nickel Failure: Nickel (Ni) thin films (15 nm) failed to support diamond growth, instead promoting catalytic graphitization and the formation of amorphous carbon, even at low deposition temperatures (~330°C).
- Iridium Success (Concept 1): Iridium (Ir) films (15 nm) proved stable and suitable for overgrowth by a fully closed diamond film when using the low-temperature Linear Antenna MWCVD system.
- Iridium Instability (Concept 2): When used in the hybrid structure (Concept 2) at high temperatures (~1000°C) in a focused plasma system, the thin Ir layer was unstable, transferring into isolated clusters that were subsequently overgrown.
- Stabilized Metallization: The Au/Ir (30/15 nm) bilayer system successfully stabilized the metallization layer, preventing diamond overgrowth and showing a strong basis for fabricating built-in and/or buried metal electrodes.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Ni/Ir/Au Layer Thickness | 15, 30/15 | nm | Single layer (Ni, Ir) or Bilayer (Au/Ir) |
| Substrate Temperature (Low T, LA-MWCVD) | ~330 | °C | Concept 1, used to avoid re-crystallization |
| Substrate Temperature (Standard T, Focused CVD) | ~1000 | °C | Concept 2, high temperature deposition |
| Substrate Temperature (Low T, Focused CVD) | 460 - 520 | °C | Concept 2, intermediate temperature deposition |
| MWCVD Power (LA-MWCVD) | 2 x 1700 | W | Linear Antenna system |
| MWCVD Pressure (LA-MWCVD) | 0.1 | mbar | Low pressure condition |
| Gas Mixture (LA-MWCVD) | H2/CH4/CO2 (200/5/20) | sccm | Low temperature recipe |
| Diamond Film Thickness (Basis Layer, D-basis*) | Approx. 70 | nm | Nanocrystalline diamond film |
| Diamond Peak (Raman) | ~1332 | cm-1 | Characteristic sharp diamond peak |
| Graphitic G-Band (Raman) | ~1540 to ~1580 | cm-1 | Detected in amorphous carbon and disordered phases |
| Trans-Polyacetylene Bonds (Raman) | ~1140 | cm-1 | Detected in low temperature deposited films |
Key Methodologies
Section titled âKey MethodologiesâThe experiment utilized two primary concepts for integrating metal layers with diamond films, employing both Linear-Antenna and Focused Plasma MWCVD systems.
- Substrate Preparation: Experiments used either flat GaN substrates (Concept 1) or thin nanocrystalline diamond (NCD) films (approx. 70 nm thick, D-basis*) deposited on Si substrates (Concept 2).
- Metal Layer Deposition: Thin metal layers (Ni, Ir, or Au/Ir bilayer) were deposited using a hybrid evaporation and sputtering system (AJA Orion 8E), followed by standard optical lithography for patterning.
- Concept 1 (Metal on Substrate): Metalized GaN was exposed to LA-MWCVD at low temperature (~330°C) using a H2/CH4/CO2 gas mixture (200/5/20 sccm) and 0.1 mbar pressure for 30 hours.
- Concept 2 (Hybrid Composite): The NCD basis layer was overcoated with the metal layer, then exposed to a second MWCVD growth step using a focused plasma system.
- Concept 2 Growth Parameters (Standard T): 3 kW power, 70 mbar, 5% CH4 and 1.5% CO2 in H2, 1000°C. This resulted in 400 nm thick films.
- Concept 2 Growth Parameters (Low T): 2.5 kW power, 30 mbar, 5% CH4 and 1.5% CO2 in H2, 460-520°C. This resulted in 70 nm thick films.
- Characterization: Surface morphology was assessed using Field-Emission Scanning Electron Microscopy (FE SEM). Film quality and phase composition were confirmed via Raman spectroscopy.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe successful fabrication of diamond-based radiation detectors with buried electrodes requires precise control over material purity, film thickness, and metal integrationâall core competencies of 6CCVD. We offer the materials and processing expertise necessary to replicate and advance the hybrid structures described in this research.
| Requirement from Research Paper | 6CCVD Solution & Capability | Technical Advantage |
|---|---|---|
| Initial Diamond Layer (D-basis)* (70 nm NCD) | Polycrystalline Diamond (PCD) wafers/plates. | We provide custom PCD films with thickness control from 0.1”m up to 500”m, easily meeting the 70 nm requirement. Available in large formats up to 125mm. |
| Epitaxial Overgrowth Layer (High Purity) | Single Crystal Diamond (SCD), Electronic Grade. | SCD films (0.1”m - 500”m) offer superior purity and crystalline quality, crucial for maximizing charge collection efficiency and defining the sensitive volume in radiation detectors. |
| Custom Metal Bilayers (Au/Ir 30/15 nm) | Internal Metalization Services (Au, Pt, Pd, Ti, W, Cu, and custom alloys). | 6CCVD provides precise, patterned metal deposition for buried electrodes. We can replicate the stabilizing Au/Ir bilayer system and optimize adhesion layers (e.g., Ti/W) to prevent clustering observed in the high-temperature Ir-only tests. |
| Hybrid Structure Fabrication (Diamond/Metal/Diamond) | Advanced MPCVD Processing & Engineering Support. | Our expertise in sequential CVD growth and process optimization allows for the successful fabrication of complex Concept 2 structures, minimizing catalytic graphitization and ensuring stable metal integration. |
| Surface Quality (Critical for lithography/contacts) | Precision Polishing Services. | We guarantee ultra-low surface roughness: Ra < 1nm for SCD and Ra < 5nm for inch-size PCD, which is essential for high-resolution lithography and reliable electrical contact formation. |
| Global Logistics | Global Shipping (DDU/DDP). | We ensure reliable, insured delivery of sensitive diamond materials worldwide, simplifying procurement for international research teams. |
Engineering Support
Section titled âEngineering Supportâ6CCVDâs in-house PhD team specializes in wide bandgap material science and can assist researchers in selecting the optimal diamond material (SCD, PCD, or Boron-Doped Diamond (BDD)) and metalization scheme for similar diamond-based radiation detector projects, ensuring compatibility with specific MWCVD recipes and temperature constraints.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Abstract Diamond is recognized as one of the most promising wide bandgap materials for advanced electronic applications. However, for many practical uses, hybrid diamond growth combining metal electrodes is often demanded. Here, we present the influence of thin metal (Ni, Ir, Au) layers on diamond growth by microwave plasma chemical vapor deposition (MWCVD) employing two different concepts. In the first concept, a flat substrate (GaN) was initially coated with a thin metal layer, then exposed to the diamond MWCVD process. In the second concept, the thin diamond film was firstly formed, then it was overcoated with the metal layer and finally, once again exposed to the diamond MWCVD. It should be mentioned that this concept allows the implementation of the metal electrode into the diamond bulk. It was confirmed that the Ni thin films (15 nm) hinder the formation of diamond crystals resulting in the formation of an amorphous carbon layer. Contrary to this finding, the Ir layer resulted in a successful overgrowth by the fully closed diamond film. However, by employing concept 2 ( ie hybrid diamond/metal/diamond composite), the thin Ir layer was found to be unstable and transferred into the isolated clusters, which were overgrown by the diamond film. Using the Au/Ir (30/15 nm) bilayer system stabilized the metallization and no diamond growth was observed on the metal layer.