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Two types of carbon nanotubes [single walled nanotubes (SWCNTs) and multi walled carbon nanotubes (MWCNTs)] are deposited on porous silicon by the drop casting technique. Upon exposure to test gas mixing ratio 3% NO 2 , the sensitivity response results show that the SWCNTs' sensitivity reaches to 79.8%, where MWCNTs' is 59.6%. The study shows that sensitivity response of the films increases with an increase in the operating temperature up to 200• C and 150℃ for MWCNTs and SWCNTs. The response and recovery time is about 19 s and 54 s at 200℃ for MWCNTs, respectively, and 20 s and 56 s at 150℃ for SWCNTs.

Tin oxide thin films were deposited by direct current (DC) reactive sputtering at gas pressures of 0.015 mbar-0.15 mbar. The crystalline structure and surface morphology of the prepared SnO 2 films were introduced by X-ray diffraction (XRD) and atomic force microscopy (AFM). These films showed preferred orientation in the (110) plane. Due to AFM micrographs, the grain size increased non-uniformly as the working gas pressure increased.

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A comparison of gas sensing performance of V2O5:Ag nanoparticles as thin film and as bulk pellet toward NO2 and NH3 is presented. V2O5:Ag nanoparticles thin films were deposited by vacuum thermal evaporation method on glass substrates while the pellets were prepared by powder technology. XRD patterns of thin film and pellet were polycrystalline with an orthorhombic structure. The value of average grain size is about 60 nm. The morphological properties of the samples have been distinguished by atomic force microscopy (AFM) and field effect scanning electron microscopy (FESEM) which indicated that the films showed homogeneous surfaces morphology and contained pores between the grains.  Sensing results showed a various response to NO2 and NH3 gases. It was found that the sensitivity of thin films sensor is superior to that of the pellets sensor.

Manganese Sulfide (MnS) thin films were prepared by thermal evaporation technique which deposited on a glass and silicon substrate. The deposited films were examined for their morphology and crystal structure by X-Ray Diffraction (XRD). The MnS heterojunction was successfully fabricated by using thermal evaporation technique at different temperature. The I-V properties of the heterogeneous MnS depend heavily on the structure. Silicon improves performance MnS shows good transparency in the spectral range 300-900 nm and the electrical properties of the system are highly dependent on the structure. The maximum value of the R (λ) spectral response of the MnS detection amplifier is 0.165 A/W at 450±50 nm. The maximum detection value of D (λ) was found around 2.359×10 12 (cm Hz-1/W) at 450±60 nm wavelength of the MnS optical amplifier.

We prepared polythiophene (PTH) with single wall carbon nanotube (SWCNT) nanocomposite thin films for Nitrogen dioxide (NO2) gas sensing applications. Thin films were synthesized via electrochemical polymerization method onto (Indium tin oxide) ITO coated glass substrate of thiophene monomer with magnesium perchlorate and different concentration from SWCNT (0.012 and 0.016) % in the presence130mL of Acetonitrile used. X-ray diffraction (XRD), Field Emission Scanning Electron microscopy (FE-SEM), Atomic Force Microscope (AFM) and Fourier Transform Infrared Spectroscopy (FT-IR) were used to characterized these nanocomposite thin films. The response of these nanocomposite for NO2 gas was evaluated via monitoring the change time in presence 25% NO2 of with electrical resistance at (40, 80,120,160 and 200)°C. We can observe that the PTh/SWCNT films show a higher sensitivity as compare to pure PTH.