Abstract:In this paper platinum (Pt) doped tungsten trioxide (WO 3 ) layers have been investigated. The structures were prepared in the standard thick film technology. A scanning electron microscope (SEM) were used for the microstructure analysis of the gas sensitive layers. The work function were examined by using a Scanning Kelvin Probe (SKP). The Kelvin probe is a non-contact and nondestructive method of work function measurements and surface analysis. This tool is very sensitive to any surface potential changes of the investigated material. The measurements preformed by using the SKP shows that the screen printed WO 3 layers are very homogenous and no significant defects are present. The Pt dopants added to the gas sensitive layer create small clusters on the surface of the WO 3 grains. The presents of those additives changes the potential barrier between the metal oxide crystals and caused a decrease of the sensing layer resistance.

Although ambient processing is the key to low-cost organic solar cell production, high-vacuum thermal evaporation of LiF is often a limiting step, motivating the exploration of solution processing of LiF as an alternative electrode interlayer. Submonolayer films are realized with the assistance of polymeric micelle reactors that enable LiF particle deposition with controlled nanoscale surface coverage. Scanning Kelvin probe reveals a work function tunable with nanoparticle coverage with higher values than that of bare indium tin oxide (ITO).

The paper presents the results of our investigation on the effect of the molecular structure of organic vapors on the characteristics of resistive chemical gas sensors. The sensors were based on tin dioxide and prepared by means of thick film technology. The electrical and catalytic examinations showed that the abstraction of two hydrogen atoms from the organic molecule and formation of a water in result of reaction with a chemisorbed oxygen ion, determine the rate of oxidation reactions, and thus the sensor performance. The rate of the process depends on the order of carbon atoms and Lewis acidity of the molecule. Therefore, any modification of the surface centers of a sensor material, modifies not only the sensor sensitivity, but also its selectivity.

In this paper, methods for selectivity improvement of semiconductor gas sensors are presented. The frequently used techniques are: temperature modulation, synthesis of new materials, designing new sensor constructions, adopting filter layers and using of sensors array. A comparison between the different methods has been made. It was concluded that the kind of sensing material and filter layer have a strong influence on the sensor parameters. The analysis has shown that the optimal detection temperature change when using multilayer gas sensors.

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