Application of a microwave acoustoelectronic sensor on a diamond substrate to determine the properties of solutions of substances
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2025-10-21 |
| Journal | Radioelectronics Nanosystems Information Technologies |
| Authors | B. P. Sorokin, Dmitry Yashin, Nikita O. Asafiev |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Microwave Acoustoelectronic Sensor on Diamond Substrate
Section titled âTechnical Documentation & Analysis: Microwave Acoustoelectronic Sensor on Diamond SubstrateâThis document analyzes the research detailing a High Overtone Bulk Acoustic Resonator (HBAR) sensor built on a Single Crystal Diamond (SCD) substrate for measuring the acoustic impedance of liquids in the microwave frequency band. The analysis highlights the critical role of the diamond substrate and connects the material requirements directly to 6CCVDâs advanced MPCVD diamond capabilities.
Executive Summary
Section titled âExecutive SummaryâThe following points summarize the key technical achievements and the core value proposition of the diamond-based acoustoelectronic sensor:
- High-Frequency Sensing: Successful development of a High Overtone Bulk Acoustic Resonator (HBAR) operating in the microwave band (4.8 GHz and 5.6 GHz) using longitudinal Bulk Acoustic Waves (BAW).
- Diamond Substrate Advantage: The sensor utilizes a 503 ”m thick, IIa type, (100) Single Crystal Diamond (SCD) substrate, which serves as the primary acoustic medium and sensing element.
- Enhanced Performance: Diamondâs superior acoustic properties enable high quality factors (Q0 up to 11,400) and allow the sensor to operate at high microwave frequencies, significantly increasing sensitivity compared to MHz-range devices.
- Multilayer Structure: The device incorporates a thin-film piezoelectric transducer (TFPT) composed of Al/Al0.72Sc0.28N/Mo deposited onto the SCD, demonstrating complex material integration capability.
- Linear Response: A strong, highly linear relationship (R2 up to 0.9716) was established between the reduced electrical reflection coefficient (S/S0) and the acoustic impedance (Z) of various aqueous solutions (NaCl, glycerol, 2-propanol).
- Chemical Robustness: The high chemical tolerance and abrasion resistance of the diamond substrate ensure the sensor can be reused indefinitely for studying a wide range of substances, including aggressive liquids, without performance degradation.
Technical Specifications
Section titled âTechnical SpecificationsâHard data extracted from the research paper detailing the sensor structure and performance metrics.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Substrate Material | Single Crystal Diamond (SCD) | N/A | IIa type, (100) orientation |
| Substrate Thickness | 503 | ”m | Diamond layer thickness |
| Operating Frequencies | 4.8 and 5.6 | GHz | Microwave band, control overtones |
| Initial Quality Factor (Q0) | 7,600 | N/A | Unloaded state, 4.8 GHz |
| Initial Quality Factor (Q0) | 11,400 | N/A | Unloaded state, 5.6 GHz |
| Outer Electrode (Al) Thickness | 177 | nm | Thin-film piezoelectric transducer (TFPT) |
| Piezoelectric Film (AlScN) Thickness | 1,900 (1.9) | nm (”m) | Al0.72Sc0.28N layer |
| Inner Electrode (Mo) Thickness | 122 | nm | Molybdenum layer |
| Test Temperature | 23 ± 0.5 | °C | Fixed ambient temperature for liquid testing |
| Linearity (R2) | 0.9716 | N/A | S/S0 vs. Acoustic Impedance (4.8 GHz) |
| Acoustic Impedance Range Tested | 0.924 - 1.963 | MRayl | Range covered by tested solutions |
Key Methodologies
Section titled âKey MethodologiesâThe following steps outline the fabrication and experimental procedures used to develop and test the diamond-based HBAR sensor:
- Substrate Growth: A single crystalline diamond substrate (IIa type, (100) orientation) was grown using the high-temperature, high-pressure Temperature Gradient Method (TGM).
- Thin-Film Piezoelectric Transducer (TFPT) Deposition: The multilayer structure, consisting of the inner electrode (Mo), the Aluminum-Scandium Nitride (Al0.72Sc0.28N) piezoelectric film, and the outer electrode (Al), was deposited onto the diamond substrate using magnetron sputtering.
- Sensor Housing: The composite structure was mounted in a metal casing containing SMA connectors and an RG405 microwave cable. The TFPT was located inside the housing for protection, while the diamondâs free surface was exposed to the analyte.
- Acoustic Wave Generation: An electrical signal was applied to the TFPT, generating a longitudinal Bulk Acoustic Wave (BAW) that propagated and reflected within the diamond substrate, producing acoustic overtones in the microwave range.
- Electrical Measurement: The complex reflection coefficient (S11) was measured as a function of frequency using an Agilent E5071C ENA Vector Circuit Analyzer (VCA).
- Data Processing: The âextractedâ electrical reflection coefficient (S11e) and the Q-factor (Qn) were calculated from the S11 data, specifically focusing on control overtones near 4.8 GHz and 5.6 GHz.
- Liquid Testing: The sensor was tested using milligram quantities of distilled water and aqueous solutions of NaCl, glycerol, and 2-propanol at various weight concentrations, confirming the linear relationship between S/S0 and the calculated acoustic impedance (Z).
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThis research validates the use of high-quality MPCVD Single Crystal Diamond (SCD) as a superior substrate for high-frequency acoustoelectronic sensors. 6CCVD is uniquely positioned to supply the materials and fabrication services required to replicate, scale, and advance this technology.
Applicable Materials and Customization
Section titled âApplicable Materials and Customizationâ| Research Requirement | 6CCVD Material Recommendation | Customization Potential & Advantage |
|---|---|---|
| High-Quality Substrate (503 ”m, IIa, (100) SCD) | Optical Grade Single Crystal Diamond (SCD) | We provide SCD plates up to 500 ”m thick with precise (100) orientation, ensuring minimal acoustic loss and high Q-factors essential for GHz-range HBAR operation. |
| Electrode Deposition (Mo, Al, Ti, etc.) | Advanced Metalization Services | The sensor requires Mo and Al electrodes. 6CCVD offers in-house deposition of refractory metals (Mo, W, Ti) and noble metals (Au, Pt, Pd, Cu) to create robust, high-adhesion thin-film stacks for TFPT integration. |
| Surface Finish (Required for thin-film growth) | Ultra-Low Roughness Polishing | Our SCD substrates are polished to an industry-leading surface roughness of Ra < 1 nm. This atomic-scale smoothness is critical for the uniform, high-quality growth of the AlScN piezoelectric layer. |
| Scaling & Dimensions (Custom sensor geometry) | Precision Fabrication Services | While the paper used a specific size, 6CCVD can supply SCD and PCD wafers up to 125mm in diameter, along with custom laser cutting and shaping to meet specific sensor array or miniaturization requirements. |
| Chemical Resistance (Aggressive liquid testing) | Chemically Inert MPCVD Diamond | Our diamond materials inherently possess the high chemical tolerance and abrasion resistance cited in the paper, guaranteeing the longevity and reusability of sensors designed for harsh chemical environments. |
Engineering Support
Section titled âEngineering Supportâ6CCVDâs in-house team of PhD material scientists and engineers specializes in optimizing diamond properties for advanced applications. We offer comprehensive support for similar Microwave Acoustoelectronic Sensing projects, including:
- Thickness Optimization: Assisting researchers in selecting the ideal SCD or PCD thickness (from 0.1 ”m to 10 mm) to tune the acoustic overtone frequencies and maximize Q-factor performance.
- Doping Control: For applications requiring conductive layers or integrated electronics, we offer Boron-Doped Diamond (BDD) films and substrates with precisely controlled conductivity.
- Global Logistics: We ensure reliable, global shipping (DDU default, DDP available) of sensitive, high-value diamond components directly to your research facility.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Rapid determination of liquid properties is essential for various fields of human endeavor, such as medicine, pharmacology, and various chemical industries. To this end, we have developed an acoustoelectronic liquid sensor based on a High overtone Bulk Acoustic Resonator using microwave longitudinal bulk acoustic waves. Sensor is designed to measure the acoustic impedance of liquids. The sensor is built on a multilayer piezoelectric structure composed of âAl/Al0.72Sc0.28N/Mo/(100) diamondâ. To protect the sensitive element from potential chemical damage from the analytes being tested, a metal housing is used, with the thin-film piezoelectric transducer âAl/Al0.72Sc0.28Nâ located within the housing. The analytes are placed on the opposite free side of the diamond substrate, and the sensor has been tested on aqueous solutions of NaCl, glycerol, and isopropyl alcohol at various concentrations. The samples weighed several milligrams. The relationship between the electrical reflection coefficients of the sensor and the acoustic impedance of liquids and solutions was found to be linear. Thanks to the high chemical tolerance and abrasion resistance of a diamond substrate, this sensor can be reused for studying a wide range of substances, including aggressive liquids, without any loss of performance.