Amit Sanger

Highly sensitive and selective CO gas sensor based on a hydrophobic SnO2/CuO bilayer

Here, we have deposited bare SnO2 and SnO2/CuO bilayer thin films directly on porous anodic alumina (AAO) by pulsed laser deposition and then used them as a gas sensor without additional processing. The bilayer sensor shows remarkably high and selective responses to CO gas compared with bare SnO2 in a low detection range 5–500 ppm. Sensor response, selectivity, and stability studies reveal excellent sensing of the thin films. The working principle and role of hydrophobicity behind their good performance was discussed.

Hydrogen sensing properties of nanostructured Pd/WO3 thin films: role of hydrophobicity during recovery process

In the present work the structural, optical and hydrogen sensing properties of Pd-capped tungsten oxide (Pd/WO3) thin films have been investigated. The nanostructured Pd/WO3 thin films have been prepared using DC magnetron sputtering on glass and Si(100) substrates at various oxygen partial pressures. The samples were hydrogenated at 2 bar hydrogen pressure in an operating temperature range 300–423 K. Optical transmittance spectra confirms fully transparent WO3 thin films deposited at oxygen partial pressure of 0.5 Pa while the transmittance drastically decreases to 50% for hydrogenated Pd/WO3 thin films. The influence of surface roughness and hydrophobicity of the Pd/WO3 thin films on the hydrogen sensing performance have been studied. Fast response time (1 sec) and an optimum recovery time (~8 min) have been observed at a moderate temperature of 323 K for the samples having roughness ~4.5 nm and contact angle ~96°. Hydrophobicity of the surface provides short recovery time by opposing the existence of water-vapour on the surface.

Fast response ammonia sensors based on TiO2 and NiO nanostructured bilayer thin films

In the present work, we have synthesized TiO2 and NiO based bilayer nanostructured thin films on glass substrates via DC magnetron sputtering at room temperature. The structural and morphological properties of the bilayer samples were systematically studied using numerous analytical techniques, including X-ray diffraction (XRD), Raman spectroscopy, atomic force microscopy (AFM), field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The ammonia (NH3) gas sensing properties of both bilayer sensors towards a low detection range (5–500 ppm) within a low operating temperature regime (30–300 °C) have been extensively discussed in detail. The TiO2/NiO and NiO/TiO2 sensors exhibited high sensing responses (Rg/Ra ∼ 7.6) and (Ra/Rg ∼ 5.0) with very fast response times (∼24 s) and (∼30 s) towards 100 ppm NH3 at 280 °C and 200 °C, respectively. Furthermore, the working principle attributed behind their good gas sensing properties was also investigated via formation of p–n and n–p heterojunctions at the interface.

Porous silicon filled with Pd/WO3–ZnO composite thin film for enhanced H2 gas-sensing performance

Here, pure ZnO, WO3 and Pd/WO3–ZnO composite porous thin films were successfully synthesized directly on porous silicon by a reactive DC magnetron sputtering technique. A sensor based on the Pd/WO3–ZnO composite porous thin films showed remarkably improved H2 sensing performance with good stability and excellent selectivity compared to that of pure WO3 and ZnO, at a relatively lower operating temperature (200 °C) and with a low detection range of 10–1000 ppm. The enhanced response can be attributed to the heterojunction formed between two dissimilar materials. The underlying mechanism behind their good performance for H2 gas was discussed in detail.

Determination of optical constants including surface characteristics of optically thick nanostructured Ti films: analyzed by spectroscopic ellipsometry

In the present work, optically thick nanostructured titanium (Ti) films of thickness ranging from ∼100 to 900 nm were deposited on a glass substrate by DC magnetron sputtering at room temperature. Microstructural and surface properties of the samples were studied by x-ray diffraction and x-ray photoelectron spectroscopy (XPS). The morphological results revealed a systematic normal grain growth mechanism with increasing thickness analyzed by a scanning electron microscope. The influence of thickness on film surface roughness has been investigated by atomic force microscopy (AFM). The optical dispersion behavior was examined by spectroscopic ellipsometry (SE) over the long wavelength range of 246-1688 nm. The experimentally observed SE parameters were theoretically fitted with Drude-Lorentz and Bruggeman effective medium approximation theory. The surface properties of the Ti film measured by XPS and AFM were further accounted for in the optical model to determine optical constants (n and k) and the obtained results are expected to be the best available for bulk Ti metal.