CHARACTERIZATION OF RF AND DC MAGNETRON REACTIVE SPUTTERED TiO 2 THIN FILMS FOR GAS SENSORS

This study presents the technology for prep aring and characterization of titanium oxide thin films with proper ties suitable for gas sensors. For preparing the samples the reactive radio frequency (RF) and direct current (DC) magnetron sputtering methods were used. The composition and microstructure of the films were studied by X-ray photoelectron spectroscopy (XPS), X-ray diff raction (XRD) and Raman spectroscopy, the surface of the films was observed applying high-resolution scanning electron microscopy (SEM). For measuring the thickness and identifying the refractive indices of the films laser ellipsometry was used. The research was focuse d on the sensing behavior of the sputtered titania thin films applying quartz crystal microbalance (QCM) method, which allows detection of mass changes in the nanogram range. Prototype QCM sensors with TiO 2 thin films were made by our team and tested for sensitivity to NH 3 and NO 2 . These films even in as-deposited state and without heating th e substrates show good sensitivity. Additional thermal treatment is not necessary, making manufacturing of QCM gas sensor simple and cost-effective, as it is fully compatible with the technology for producing the initial resonator. The sorption is fully reversible and the studied TiO 2 films are stable, which makes them capable for meas urements for long terms

Characterization of thin MoO3 films formed by RF and DC-magnetron reactive sputtering for gas sensor applications

The present work discusses a technology f or deposition and characterization of thin molybdenum oxide (MoO x , MoO 3 ) films studied for gas sensor applications. T he samples were produced by reactive radio - frequency (RF) and direct c urrent (DC) magnetron sputtering. The composition and microstructure of the films were studied by XPS , XRD and Raman spectroscopy, the morphology , using high resolution SEM. T he research was focused on the sensing properties of the sputtered thin MoO 3 films. Highly sensitive gas sensor s were implemented by depositing films of various thicknesses on quartz resonators. Making use of the quartz crystal microbalance (QCM) method , the se sensors we re capable of detect ing chan ges in the molecular range. Prototype QCM structures with thin MoO 3 films were tested for sensitivity to NH 3 and NO 2 . E ven in as - deposited state and without heating the substrates, these films show ed good sensitivity . Moreover , no a dditional thermal treatment is necessary, which makes the production of such QCM gas sensor s simple and cost - effective, as it is fu lly compatible wit h the technology for producing t he initial resonator . Т he films are sensitive at room temperature and can reg ister concentrations as low as 50 ppm . The sorption is fully reversible , the films are stable and capable of long - term measuremen ts

Optical measurements of electrophoretic suspension kinetics

Electrophoretic deposition (EPD) was originally used for formation of coatings, e. g. in the automotive industry. Recently EPD is successfully utili zed for thin film preparation with an app lication in the optics and electronics. This paper investigates the process of the suspension formation and aggregation by ultraviolet and visible spectroscopy (UV- VIS) spectroscopy and Dynamic Light Scattering (DLS) methods. The suspensions were formed by a precipitation of solution of poly[2-methoxy-5-(3 ′ ,7 ′ -dimethyloctyloxy)-1,4-phenylenevinylene] in toluene using acetonitrile as a precipitator. It could be concluded that the progressive suspension particle growth observed by DLS affects regularly the first derivative of the UV-VIS spectra. By a comparison of the results obtained by both methods it could be seen that UV-VIS spectroscopy combined with the spline method could be successfully used for an estimation of electrophoretic suspensions

Characterization of PLD grown WO3 thin films for gas sensing

Tungsten trioxide (WO3) thin films were grown by pulsed laser deposition (PLD) with the aim to be applied in gas sensors. The films were studied by atomic force microscopy (AFM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and profilometry. To study the gas sensing behavior of these WO3 films, they were deposited on quartz resonators and the quartz crystal microbalance (QCM) method was applied to analyze their gas sensitivity. Synthesis of tetragonal-WO3 films starting from a target with predominantly monoclinic WO3 phase was observed. The films deposited at 300 degrees C presented a surface topology favorable for the sorption properties, consisting of a film matrix with protruding craters/cavities. QCM prototype sensors with such films were tested for NO2 sensing. The PLD grown WO3 thin films show good sensitivity and fast reaction at room temperature, even in as-deposited state. With the presented technology, the manufacturing of QCM gas sensors is simple, fast and cost-effective, and it is also suitable for energy-effective portable equipment for on-line monitoring of environmental changes. (C) 2017 Elsevier B.V. All rights reserved