Enhanced gas sensing capabilities of diamond layers using Au nanoparticles

The nanocrystalline diamond (NCD) film reveals a unique combination of physical, chemical, and optoelectronic properties, which makes it a promising material for various sensing applications. To improve a gas sensor's response, selectivity, or reproducibility, its surface is often modified with specific terminations, functional groups or (bio)molecules, thin films, etc. In this work, the NCD surface modification was achieved by a) layer morphology variation using two different types of chemical vapor deposition (CVD) systems, b) top surface termination (H-NCD and O-NCD), and c) Au nanoparticles (Au NPs). The properties of each structure are measured, compared and subsequently evaluated. The electrical properties (resistance changes) are measured for two types of active gas (oxidizing gas NO2 and reducing gas NH3) in a temperature range from 22 degrees C to 125 degrees C. Neutral synthetic air (80 % nitrogen and 20 % oxygen) was applied for flushing and resetting the sensors. Thin film fabrication, surface analysis (scanning electron microscopy and Raman spectroscopy), and measurement of electrical properties are described. Surface morphology greatly influences gas response because a large active surface area (higher roughness or 3D-like surface) enhances interaction with gas molecules. While the termi-nation of the NCD with hydrogen is essential for the functionality of the gas sensor, the Au NPs further enhanced the dynamic response of the sensor and magnitude.

Automated summary

The nanocrystalline diamond (NCD) film is a promising material for various sensing applications due to its unique combination of physical, chemical, and optoelectronic properties. In this study, the surface of NCD was modified using different methods, such as variation in layer morphology, surface termination (H-NCD and O-NCD), and the addition of Au nanoparticles (Au NPs). The properties of each modified structure were measured, compared, and evaluated. The gas response of the modified NCD films was tested using oxidizing gas NO2 and reducing gas NH3, and the electrical properties were measured in a temperature range from 22 degrees C to 125 degrees C.