A. Brudnik

Reactively sputtered TiO2−x thin films with plasma-emission-controlled departure from stoichiometry

Thin films of TiO 2-x with reproducible optical and structural properties were deposited by d.c. reactive magnetron sputtering. The automatic control of the sputtering conditions was attained by monitoring the emission line of metallic Ti at A = 500 nm and by using this signal as a feedback to operate the gas admission system. Grazing incidence diffraction (GID) revealed formation of the anatase-rutile mixtures in all deposited films. Spectrophotometric measurements showed a shift in the fundamental absorption edge from 3.4 to 3.2 eV that could be traced back to the diminishing amount of the anatase phase in films deposited at high sputtering rates. The change in the refractive index from 2.3 to 2.45 was also observed.

Thin film metal oxide gas sensor array for gas detection

This paper presents how an array of sensors with various sensitivities can be used for reliable detection and recognition of gases. An array of six different thin film metal oxide gas sensors has been constructed and tested. The selected sensors are based on indium, zinc, tin and titanium thin film oxides deposited by reactive magnetron sputtering. Sensors operate inside a measuring chamber at elevated temperatures of 250 – 300°C. The sensors responses upon hydrogen and ammonia exposure (0 – 3000 ppm) at relative humidity (0 – 75%Rh) are studied. The results show that exploiting the cross sensitivity and different sensing performance of the sensors allows to increase the reliability of gas sensing at relatively low operating temperatures.

Measurement system for resistive metal oxide sensors matrix

The measurement system for laboratory array of gas sensors was constructed. The system can be used to measure the response characteristic of resistive metal oxide (MOx) gas sensors. Proposed system is flexible and reconfigurable easy, to perform high and low resistivity measurements.

Metal oxide gas sensors upon various temperature-induced profiles

This paper presents how an array of sensors with different sensitivities to gases can be applied for detection of hydrogen in the presence of humidity when operated upon various temperature - induced profiles. The sensors in the array are subject to temperature modulation over the range of 350 – 500°C. Temperature profiles are based on a cardinal sine as well as Meyer wavelet phi and psi functions. Changes in the sensor operating temperature lead to distinct resistance patterns of the sensors depending on gas concentration. The sensors responses are studied as a function of target gas concentration (0 – 3000 ppm) and relative humidity level (0 – 75%Rh). Feedforward back-propagation neural networks are used in order to facilitate gas concentration and humidity level prediction. The results show reliable hydrogen detection upon temperature modulation and a reduction of the total power consumption.