Self-powered, flexible and room temperature operated solution processed hybrid metal halide p-type sensing element for efficient hydrogen detection

Hydrogen (H2) is a well-known reduction gas and for safety reasons is very important to be detected. The most common systems employed along its detection are metal oxide-based elements. However, the latter demand complex and expensive manufacturing techniques, while they also need high temperatures or UV light to operate effectively. In this work, we first report a solution processed hybrid mixed halide spin coated perovskite films that have been successfully applied as portable, flexible, self-powered, fast and sensitive hydrogen sensing elements, operating at room temperature. The minimum concentrations of H2 gas that could be detected was down to 10 ppm. This work provides a new pathway on gases interaction with perovskite materials, launches new questions that must be addressed regarding the sensing mechanisms involved due to the utilization of halide perovskite sensing elements while also demonstrates the potential that these materials have on beyond solar cell applications

Long-term stability of transparent n/p ZnO homojunctions grown by rf-sputtering at room-temperature

ZnO-based n/p homojunctions were fabricated by sputtering from a single zinc nitride target at room temperature on metal or ITO-coated glass and Si substrates. A multi-target rf-sputtering system was used for the growth of all oxide films as multilayers in a single growth run without breaking the vacuum in the growth chamber. The nitrogen-containing films (less than 1.5 at.% of nitrogen) were n-type ZnO when deposited in oxygen-deficient Ar plasma (10% O2) and p-type ZnO when deposited in oxygen-rich Ar plasma (50% O2). The all-oxide homojunction ITO/n-ZnO/p-ZnO/ITO/glass was fabricated in a single deposition run and exhibited visible transparency in the range of 75–85%. The n/p ZnO homojunctions, having metallic contacts, formed on conventionally processed substrates showed a fairly unstable behavior concerning the current-voltage characteristics. However, the same homojunctions formed on Si3N4-patterned substrates and stored in atmosphere for a period of five months were stable exhibiting a turn-on voltage of around 1.5 V. The realization of a room temperature sputtered transparent and stable ZnO homojunction paves the way to the realization of all-oxide transparent optoelectronic devices

Highly sensitive and selective NO2 chemical sensors based on Al doped NiO thin films

Al-doped Nickel oxide (Al:NiO) nanostructured thin films, prepared by RF sputtering technique, were tested for NO2 gas detection. The films were deposited on alumina substrates with thicknesses ranging between 52 nm and 167 nm, while the at.% of Al was varied from 5.0% to 6.7%. The effect of the thickness on the morphological, structural and optical properties was investigated. Moreover, the sensing characteristics were examined and optimized with respect to film thickness and operating temperature (200 °C and 300 °C), at NO2 concentrations ranging from 200 ppb to 2500 ppb and in presence of a constant relative humidity (RH) of 40%. An ultimate response of 271% towards a NO2 concentration of 200 ppb at 200 °C was obtained, concluding that Al:NiO can be potentially used as a sensing material for this specific gas

Sputtering power and deposition pressure effects on the electrical and structural properties of copper thin films

We investigated the effects of sputtering power and deposition pressure on the electrical and structural properties of dc magnetron sputter-deposited copper films on p-type silicon grown at room temperature. Results from our experiments showed that the deposition rate of the copper films increased proportionally with the sputtering power. Sputtering power also affected the structural properties of the copper films through the surface diffusion mechanism of the adatom. From the scanning electron microscopy surface analysis, the high sputtering power favored the formation of continuous film. The poor microstructure with voided boundaries as a result of low sputtering power deposition was manifested with the high resistivity obtained. The deposition rate was found also depending on the deposition pressure. The deposition pressure had the contrary effect on structural properties of copper films in which high deposition pressure favored the formation of voided boundaries film structure due to the shadowing effect, which varied with different deposition pressure. (c) 2005 Springer Science + Business Media, Inc