Development of SiC-FET methanol sensor

Abstract

A silicon carbide based field effect transistor (SiC-FET) structure was used for methanol sensing. Due to the chemical stability and wide band gap of SiC, these sensors are suitable for applications over a wide temperature range. Two different catalytic metals, Pt and Ir, were tested as gate contacts for detection of methanol. The sensing properties of both Ir gate and Pt gate SiC-FET sensors were investigated in the concentration range 0.3 -5% of methanol in air and in the temperature range 150-350ºC. It was observed that compared to the Ir gate sensor, the Pt gate sensor showed higher sensitivity, faster response and recovery to methanol vapour at comparatively lower temperature, with an optimum around 200ºC. Quantum-chemical calculations were used to investigate the MeOH adsorption and to rationalize the observed non-Langmuir behavior of the response functions. The methanol sensing mechanism of the SiC-FET is discussed.

SiC-FET methanol sensors for process control and leakage detection

“…Similar to the earlier study for higher concentrations of methanol [9], the cross sensitivity to hydrogen and propene was also studied for the lower concentrations of methanol investigated in this paper. Besides, changes in response characteristics of the sensors towards different oxygen concentrations in the carrier gas and the influence of humidity are also reported in the present work.…”

“…2 in the same way as described in the previous study [9]. Response was defined as the difference between the sensor signal when the test gas was introduced and the baseline.…”

“…9 shows the responses at methanol concentration of 20, 400, 800, 1600, and 50000 ppm in 10% or 20% oxygen, which reveals a shift in the temperature for optimum response. The results for 50000 (5%) of methanol are taken from reference [9]. In the presence of oxygen for Pt-gate sensors in Fig.…”

“…Hydrogen-containing gases like methanol, will typically dissociate upon adsorption on the sensor surface and released hydrogen will form a layer of polarized OH groups on the (gate) insulator surface, which will change the conductivity of the channel between source and drain in the transistor device, which in turn causes a change of the voltage-current profile [7] [8].. In our earlier study, J. Kanungo et al reported the characteristics of SiC-FET sensors where either porous Pt or Ir metal were used as gate material for the detection of gaseous methanol in high concentrations (0.3-5%) [9]. We concluded that the Pt sensors Besides hydrogen and propene, a study of the influence of different oxygen concentrations in the carrier gas has been carried out, as well as the influence of humidity.…”

Fabrication and Characterization of a Micro Methanol Sensor Using the CMOS-MEMS Technique

“…Methanol sensors can be applied in electronic noses [ 1 , 2 ], fuel cells [ 3 ], disease diagnosis [ 4 ] and environment Monitoring [ 5 ]. Various microsensors [ 6 , 7 ] have been developed using micromachining technology.…”