Aluminum-mesoporous silicon coplanar type structure for methanol gas sensing

In this paper, we treat gas sensing properties of porous silicon layer (PSL) towards methanol (MeOH) gas. For this purpose an Al/meso-PS/c-Si/meso-PS/Al coplanar type structure has been achieved. The current flowing throughout the structure enhances as MeOH concentration increases. The experimental values of the effective electrical conductivity are estimated from the serial resistance (Rs) of the structure. The values of Rs are deduced from the dark I–V characteristics. We found that the conductivity increases as MeOH concentration increases. The sensor exhibits quasi-reproducible I–V characteristics subsequent to several MeOH adsorption/desorption cycles. The MeOH molecules are desorbed by a simple nitrogen flushing. Additionally, Fourier transform infrared (FTIR) spectroscopy revealed that the surface of meso-PS turns back to its initial structure surface once removing MeOH molecules, indicating a reversible behavior of the sensor. Effective medium theory (EMT) was used to model optical and structural features of the PSL. From FTIR spectra, we deduced the experimental refractive index values of the meso-PSL as a function of MeOH, which agree with theoretical values obtained using the Bruggeman effective medium theory (EMT).