Peculiarities of the Acoustic Wave Propagation in Diamond-Based Multilayer Piezoelectric Structures as “Me1/(Al,Sc)N/Me2/(100) Diamond/Me3” and “Me1/AlN/Me2/(100) Diamond/Me3” under Metal Thin-Film Deposition
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2022-01-07 |
| Journal | Electronics |
| Authors | Г. М. Квашнин, B. P. Sorokin, Nikita O. Asafiev, V.M. Prokhorov, A. V. Sotnikov |
| Institutions | Technological Institute for Superhard and Novel Carbon Materials, Leibniz Institute for Solid State and Materials Research |
| Citations | 8 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Diamond-Based HBAR Sensors
Section titled “Technical Documentation & Analysis: Diamond-Based HBAR Sensors”Reference Paper: Kvashnin et al. (2022). Peculiarities of the Acoustic Wave Propagation in Diamond-Based Multilayer Piezoelectric Structures… Electronics 2022, 11, 176.
Executive Summary
Section titled “Executive Summary”This research validates the use of Single Crystal Diamond (SCD) substrates in High Overtone Bulk Acoustic Resonators (HBARs) as a superior platform for ultra-sensitive, high-frequency acousto-electronic sensors.
- Core Achievement: Successful fabrication and testing of diamond-based Multilayer Piezoelectric Structures (MPS) operating as mass sensors in the microwave band.
- Material Validation: Synthetic Single Crystal Diamond (SCD) Type IIa substrates were confirmed to maintain exceptionally high Quality Factors (Q) up to 12,500 at frequencies near 20 GHz.
- High Frequency Operation: The HBAR devices demonstrated stable operation and high Q-factors across the 1 GHz to 20 GHz range, with potential for extension up to 40 GHz, significantly exceeding conventional SAW or FBAR sensors.
- Enhanced Sensitivity Mechanism: Optimal sensor sensitivity was achieved by exploiting the acoustic impedance mismatch between the diamond substrate (Zdiam) and the deposited metal film (Me3), particularly at specific quarter-wave thickness points.
- Structure: The sensors utilized a five-layered structure: Me1/(Al,Sc)N/Me2/(100) diamond/Me3, requiring precise control over thin-film deposition and material properties.
- Commercial Potential: The resulting diamond-based sensors offer enhanced sensitivity, chemical inertness, high temperature resistance, and potential for multiple applications, positioning them as a prospective platform for next-generation multipurpose sensors.
Technical Specifications
Section titled “Technical Specifications”The following hard data points were extracted from the experimental results and modeling parameters:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Substrate Material | Single Crystal Diamond (SCD) | N/A | Type IIa, (001) orientation |
| Operating Frequency Range | 1 to 20 | GHz | Tested range for HBAR sensor |
| Maximum Quality Factor (Q) | ~12,500 | N/A | Observed at ~20 GHz |
| L-BAW Phase Velocity (Diamond) | 17,542 | m/s | Along [100] direction |
| Acoustic Impedance (Diamond) | 61.7 x 106 | kg/m2·s | Reference value for sensitivity calculation |
| Diamond Substrate Thickness | 482, 501, 629 | µm | Used in Sensors #A, #B, #C |
| Piezoelectric Layer Thickness | 930 to 1120 | nm | AlN or Al1-xScxN |
| Sc Content in Piezoelectric Layer | 0 to 13 | % | Used to enhance electromechanical excitation |
| Deposited Film Thickness (Me3) | 0 to 950 | nm | Range studied for Sc, Mo, and Pt films |
| Electrode Materials (Me1, Me2, Me3) | Al, Mo, Pt, Sc | N/A | Metals used in the multilayer stack |
Key Methodologies
Section titled “Key Methodologies”The experimental procedure focused on precise material synthesis, thin-film deposition, and high-frequency acoustic characterization.
- Substrate Selection: Type IIa synthetic Single Crystal Diamond (SCD) plates with (001) orientation were chosen for their exceptionally low acoustic attenuation in the microwave band.
- Multilayer Structure Fabrication: HBAR sensors were realized as five-layered Multilayer Piezoelectric Structures (MPS): “Me1/(Al,Sc)N/Me2/(100) diamond/Me3”.
- Piezoelectric Transducer Deposition: Thin-film piezoelectric transducers (TFPT) of Aluminum Nitride (AlN) or Aluminum-Scandium Nitride (Al,Sc)N were applied to excite the Longitudinal Bulk Acoustic Wave (L-BAW).
- Metal Film Deposition (Me3): Films of Scandium (Sc), Molybdenum (Mo), and Platinum (Pt) were deposited onto the free side of the diamond substrate using AJA Orion 8 magnetron sputtering equipment.
- Thickness Metrology: Film thickness was controlled during sputtering via a Quartz Crystal Microbalance (QCM) sensor and verified post-deposition using Atomic Force Microscopy (AFM) on accompanying Si samples (measurement uncertainty 3 nm to 10 nm).
- Acoustic Characterization: The shift of the overtone’s resonant frequency (Δf/f) and Quality Factor (Q) were measured using an E5071C Agilent network analyzer. Overtones with the highest Q-factor were prioritized.
- Modeling and Simulation: Finite Element Method (FEM) simulations, utilizing COMSOL Multiphysics software, were performed to model 2D acoustic wave propagation and explain the observed dependencies based on acoustic impedance ratios.
6CCVD Solutions & Capabilities
Section titled “6CCVD Solutions & Capabilities”6CCVD provides the foundational diamond materials and advanced processing required to replicate, optimize, and scale the diamond-based HBAR technology described in this research. Our expertise in MPCVD diamond growth and precision fabrication directly addresses the critical material requirements for high-performance acousto-electronic devices.
Applicable Materials for HBAR Substrates
Section titled “Applicable Materials for HBAR Substrates”The high Q-factor performance relies entirely on the low acoustic attenuation of the diamond substrate. 6CCVD specializes in providing the necessary material quality:
- Optical Grade Single Crystal Diamond (SCD): Required to match or exceed the Type IIa quality used in the study. Our SCD material offers extremely low defect density and surface roughness (Ra < 1 nm), ensuring minimal acoustic scattering and maximum Q-factor stability up to 40 GHz.
- Custom Substrate Thickness: The paper utilized substrates up to 629 µm thick. 6CCVD offers SCD plates with thicknesses ranging from 0.1 µm up to 500 µm, and custom substrates up to 10 mm thick, allowing engineers to precisely tune the acoustic path length for specific overtone frequencies.
- Precise Orientation: We guarantee precise (001) orientation control, which is critical for maximizing L-BAW excitation efficiency and predictability in the MPS stack.
Customization Potential for MPS Fabrication
Section titled “Customization Potential for MPS Fabrication”Replicating the complex multilayer structure requires tight control over dimensions and metal interfaces. 6CCVD offers comprehensive services to streamline the fabrication process:
| Research Requirement | 6CCVD Capability | Technical Advantage |
|---|---|---|
| Metalization (Me1, Me2, Me3) | In-House Metal Deposition: We offer deposition of Au, Pt, Pd, Ti, W, and Cu. | Directly supports the use of Pt and Mo (used in the study) and allows for optimization with other high-performance metals (e.g., Ti/Pt/Au stacks). |
| Custom Dimensions & Apertures | Precision Laser Cutting & Patterning: Plates/wafers up to 125 mm (PCD) and custom patterning for SCD. | Enables precise definition of the 10,000 sq. micron aperture area and facilitates the scaling of HBAR arrays for commercial production. |
| Surface Finish | Ultra-Low Roughness Polishing: Ra < 1 nm (SCD). | Essential for minimizing acoustic losses and ensuring high-quality, uniform deposition of the piezoelectric (AlN/AlScN) and metal films. |
| Global Supply Chain | Global Shipping (DDU/DDP): | Ensures rapid and reliable delivery of custom diamond substrates to research and manufacturing facilities worldwide. |
Engineering Support
Section titled “Engineering Support”The successful operation of the HBAR sensor depends on optimizing the acoustic impedance ratio (ZMe3 vs. Zdiam). 6CCVD’s in-house PhD team specializes in material science and acoustic properties of diamond. We can assist with:
- Material Selection: Consulting on the optimal SCD grade and thickness to achieve target Q-factors and resonant frequencies for similar high-frequency acoustic sensor projects.
- Design Optimization: Providing data and support for modeling the acoustic impedance mismatch to maximize gravimetric sensitivity, particularly for novel thin-film materials.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
New theoretical and experimental results of microwave acoustic wave propagation in diamond-based multilayer piezoelectric structures (MPS) as “Me1/(Al,Sc)N/Me2/(100) diamond/Me3” and “Me1/AlN/Me2/(100) diamond/Me3” under three metal film depositions, including the change in the quality factor Q as a result of Me3 impact, were obtained. Further development of our earlier studies was motivated by the necessity of creating a sensor model based on the above fifth layered MPS and its in-depth study using the finite element method (FEM). Experimental results on the change in operational checkpoint frequencies and quality factors under the effect of film deposition are in satisfactory accordance with FEM data. The relatively small decrease in the quality factor of diamond-based high overtone bulk acoustic resonator (HBAR) under the metal layer effect observed in a wide microwave band could be qualified as an important result. Changes in operational resonant frequencies vs. film thickness were found to have sufficient distinctions. This fact can be quite explained in terms of the difference between acoustic impedances of diamond and deposited metal films.
Tech Support
Section titled “Tech Support”Original Source
Section titled “Original Source”References
Section titled “References”- 2007 - Detection of individual gas molecules adsorbed on graphene [Crossref]
- 2006 - Characterization of vaccinia virus particles using microscale silicon cantilever resonators and atomic force microscopy [Crossref]
- 2012 - Taking whispering gallery-mode single virus detection and sizing to the limit [Crossref]
- 2004 - Ultrasensitive nanoelectromechanical mass detection [Crossref]
- 1959 - Verwendung von Schwingquarzen zur Wägung dünner Schichten und zur Mikrowägung [Crossref]
- 1972 - Investigation of film-thickness determination by oscillating quartz resonators with large mass load [Crossref]
- 1993 - Quartz crystal microbalance for the detection of microgram quantities of human serum albumin: Relationship between the frequency change and the mass of protein adsorbed [Crossref]
- 2016 - Progresses on the theory and application of quartz crystal microbalance [Crossref]
- 2007 - Enhanced sensitivity of SAW gas sensor coated molecularly imprinted polymer incorporating high frequency stability oscillator [Crossref]
- 2008 - Highly sensitive mass sensor using film bulk acoustic resonator [Crossref]