Critical Influence of Dielectric Sensitive Material and Manufactured Process in Microwave Gas-Sensing: Application of Ammonia Detection with an Interdigital Sensor

Abstract

In this paper, authors propose a study on microwave gas sensors and the influence of critical key parameters such as the sensitive material and the circuit conception process. This work aims to determine the influence of these parameters on the quality of the final response of the microwave gas sensor. The fixed geometry of the sensor is a microstrip interdigital capacitor coated with a sensitive layer excited with two 50 Ω SMA ports. The sensitive material has been chosen in order to interact with the target gas: ammonia. Indeed, this gas interacts with phthalocyanine and metal oxides like hematite, TiO 2 . To explore the effect of the circuit manufacturing process, three series of samples are prepared. The first series of sensors is produced by classical UV photolithography (process) in the laboratory. The second series of sensors is produced by a subcontractor specialized in rf circuits. The third series is obtained by the experimental platform of the FEMTO-ST laboratory with EVG620 Automated Mask Alignment System Nanoimprint lithography in a clean room. To examine the reliability of this gas sensor at room temperature, it was exposed to different ammonia gas concentrations from 100 to 500 ppm in an argon flow to eliminate coadsorption phenomena. According to the recorded frequency responses, the reflection and transmission coefficients show a change of resonance amplitude due to electrical characteristic modification. This can be correlated to the presence of gaseous ammonia. The chemical nature of the sensitive material layer has a major influence at the excited frequency range. The process of conception influences the sensor sensitivity. The analysis of the results shows a strong correlation between the injected ammonia concentration and its frequency response. The influence of the critical key parameters cited is discussed here.

NiWO4 Microflowers on Multi-Walled Carbon Nanotubes for High-Performance NH3 Detection

“…Therefore, it is of great significance to study ammonia sensors with high sensitivity and high response that can be widely used. , A resistive semiconductor gas sensor is widely regarded due to its simple process, low cost, and portability. Its principle is that the electrical signal of the material changes through the electron transfer between the surface of the sensitive material and the gas molecule, such that the surface structure of the sensitive material is one of the main factors in determining the gas-sensitive performance. , Tungstate materials have attracted extensive attention in the field of gas sensing because of their excellent surface structure controllability, structural stability, and good electron transport capacity, and thus have become the research focus of resistance semiconductor gas-sensitive materials. , …”

Passive Resonant Sensors: Trends and Future Prospects

“…In the case of ammonia detection, TiO2 is used as supersubstrate for interdigital microstrip circuit (2 ports) [67]. Ammonia molecules (100-500 ppm) were adsorbed on sensitive material which coordinates NH3 and NH4 + (surface Lewis acidity) [68]. A reversible variation of the response magnitude, image of the ammonia concentration, is observed, the shift is close to -0.17 dB for S11 and + 0.1 dB for S21 (~ 2.2 GHz) at 500 ppm of ammonia (Fig.…”

On‐Site Detection for Hazardous Materials in Chemical Accidents

“…Therefore, the detection of NH 3 , based on nanomaterials has been extensively studied as necessary research for industrials applications, life‐saving, and environment protection. Nowadays, there is a series of studies on highly sensitive, selective, fast, and low cost of NH 3 sensors such as novel nanocomposites (Figure 1(c)), 61 microwave, 62 interestingly ultrahigh selective NH 3 detection in the concentration range from 0.1 parts per quadrillion (ppq) to 75 000 parts per million (ppm) based on nanocomposite—polysaccharide and plasmonic metal gold nanoparticles (AuNPs)—at the room temperature 63 . Furthermore, the NH 3 vapor sensors in the range from 20 to 100 ppm were estimated using a novel material as multiwall carbon nanotubes functionalized by polyaniline via in situ chemical polymerization process of aniline, while multiwall carbon nanotubes were sprayed coating on the fabric for wearable NH 3 sensor 64 …”