Preparation of nanocrystalline Pd/SnO2 thin films deposited on alumina substrate by reactive magnetron sputtering for efficient CO gas sensing

We have prepared nanocrystalline Pd/SnO2 thin films deposited on alumina substrate by reactive magnetron sputtering for highly sensitive and selective CO gas sensing. The deposited thin films have a nanocrystalline nature and uniform granular morphologies as characterized by GIXRD and FESEM, respectively. The oxidation states and defect states were measured using XPS and PL spectra, respectively. The sensing performance of samples for CO gas was recorded at different conditions. An enhanced sensing performance of Pd/SnO2 (sensor response, SR -90.5% with fast response/recovery time -15 s/34 s) was achieved compared to pristine-SnO2 film (SR -81.7% and response/recovery time -60 s/98 s) for 91 ppm CO gas at 200 ? operating temperature. Further, Pd/SnO2 film exhibits an excellent SR -65.5% even at 100 C operating temperature. Thus, the prepared nanocrystalline Pd/SnO2 thin films can be used for the fabrication of CO gas sensors with efficient sensing performance

Magnetron configurations dependent surface properties of SnO2 thin films deposited by sputtering process

The effect of balanced magnetron (BM) and unbalanced magnetron (UBM) configurations, in RF sputtering process, on the surface properties of SnO2 thin films has been investigated. X-ray photoelectron spectroscopy (XPS) Sn3d and O1s core spectra reveal that the films deposited at RF power of 250 W under BM configuration consist of Sn4+ oxidation states, while those deposited under UBM configuration consist of Sn4+ and Sn2+ oxidation states. This has been attributed to the migration of oxygen atoms from SnO2, resulting in the formation of Sn interstitial and oxygen vacancies. The contact angle (theta) recordings reveal that the UBM configuration results in more hydrophobic surface (140.6 degrees) of SnO2 thin films than that under BM configuration (129.6 degrees). Further, Atomic Force Microscopy (AFM) and Field Emission Scanning Electron Microscopy (FESEM) results indicate that the SnO2 thin films deposited under UBM configuration have better density with granular grains in comparison to that under BM configuration. The present studies establish the fact that magnetron configurations in sputtering process have significant impact on the surface properties of SnO2 thin films

Influence of magnetron configurations on the structure and properties of room temperature sputtered ZnO thin films

Under the unbalanced magnetron (UBM) sputtering process, not only the plasma is confined near the target like in the conventional balanced magnetron (BM) sputtering process, but also extends towards the substrate and support the ion-assisted deposition (surface of thin films is bombarded by energetic Ar+ ions during the sputtering process). Here, we report the influence of magnetron configurations on the structure and properties of room temperature sputtered ZnO thin films while keeping other process parameters fixed. The UBM configuration has significantly improved various properties of ZnO thin films in comparison to the BM configuration. The crystalline quality with dominant orientation (002) and uniform distribution of grains is observed while an increase in the band gap from 3.25 eV (BM) to 3.33 eV (UBM) is obtained. The lower defects as investigated from Zn2p and O1s core level XPS spectra, which is well supported by Photoluminescence measurements. In addition to that, surface hydrophobicity has been increased from 121.2 degrees (BM) to 125.5 degrees (UBM). Thus, the unbalanced magnetron configuration in the sputtering process significantly enhanced the structural, optical and surface properties of ZnO thin films even at room temperature and low plasma power without any post annealing treatments, which is highly desired for the device fabrication

Room temperature sputtered nanocrystalline SnO2 thin films sensitized with Pd nanoparticles for high performance CO gas sensing application

In the present work, we have reported that Pd sensitized nanocrystalline SnO2 thin films sputtered at room temperature are quite promising for development of CO gas sensors. The investigation of materials quality and to understand the sensing mechanism, various characterization techniques such as the GIXRD, FESEM, PL and XPS were used. The sensing characteristics of prepared samples have been measured for different concentration of CO gas and at different temperatures. An excellent sensor response (similar to 94.5%) has been achieved for Pd sensitized SnO2 at 100 degrees C temperature for CO gas of 91 ppm concentration than SnO2 thin film (sensor response similar to 13.6%). The maximum sensor responses similar to 99.5% and similar to 84.3% were observed at 200 degrees C temperature, respectively for both samples. Also, a very fast response and recovery time of about similar to 8 s and similar to 15 s was achieved for Pd sensitized SnO2 thin film. Further, it was observed that Pd sensitized SnO2 thin film was highly selective for CO gas compared to NH3, H2S, NO2 and NO gases and highly stable even after preserved for about six months. Thus, rough surface or nano-pillars/cracks on the surface can also improve the gas sensing