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Process-Structure-Property Relationships in Boron-Doped CVD Diamond Films on Si3N4 for Biosensor Applications
Susana Ferreira1,2,3, André Costa Vieira2, Miguel Neto3
1Department of Mechanical Engineering and Industrial Management, Superior Technological School, Institute Polytechnic of Viseu, 3504-510 Viseu, Portugal.
Materials (Basel, Switzerland)
|July 28, 2026
Summary
Researchers developed boron-doped diamond films on silicon nitride for implantable biosensors. These films show promising electrical properties and surface chemistry for enhanced glucose monitoring applications.
Area of Science:
- Materials Science
- Electrochemistry
- Biotechnology
Background:
- Implantable electrochemical biosensors require robust, biocompatible materials with specific electrical and surface properties.
- Silicon nitride (Si3N4) is a biocompatible ceramic suitable for implantable devices.
- Boron-doped diamond (BDD) offers excellent electrochemical performance and stability.
Purpose of the Study:
- To investigate the direct growth of boron-doped diamond films on silicon nitride substrates using hot-filament chemical vapor deposition (HFCVD).
- To establish process-structure-property relationships for BDD films relevant to implantable biosensor performance.
- To analyze the effects of deposition parameters on film microstructure, surface chemistry, wettability, and electrical behavior.
Main Methods:
- Hot-filament chemical vapor deposition (HFCVD) was employed to grow boron-doped diamond films on silicon nitride (Si3N4) substrates.
- Systematic variation of deposition parameters including methane concentration, deposition pressure, and sample holder configuration.
- Comprehensive characterization of film properties: microstructure, crystallographic orientation, surface chemistry, wettability, and electrical resistivity.
Main Results:
- Microcrystalline diamond films with preferential (111) orientation were achieved at low CH4/H2 ratios, facilitating boron incorporation and achieving target resistivity (1-10 kΩ).
- Surface analysis indicated partially hydrogen-terminated diamond layers with oxygen-containing functional groups (C-O, C-O-C), promoting wettability for enzyme immobilization.
- Optimal deposition conditions (150 mbar, low methane flow) yielded films with a balanced combination of electrical conductivity, surface wettability, and microstructural stability.
Conclusions:
- Direct growth of boron-doped diamond on Si3N4 via HFCVD is feasible for implantable biosensor applications.
- Process-structure-property relationships were established, guiding the development of tailored BDD films.
- The developed BDD/Si3N4 platform demonstrates potential as a robust, biocompatible material for implantable electrochemical biosensors, particularly for glucose monitoring.
