Arsen Z. Adamyan

Smoke sensor with overcoming of humidity cross-sensitivity

Abstract The influence of the environmental humidity on the sensors based on a thin-film γ-Bi2O3 is investigated. It is shown that relative humidity affects smoke sensing performances. To overcome the humidity cross-sensitivity, a new version of high sensitive smoke sensor with corresponding alterations in its design is proposed. The optimal operation mode when humidity cross-sensitivity becomes negligible and the smoke sensitivity reaches its maximal value is revealed. The time characteristics of the sensors under influence of the various concentration air–smoke mixtures are studied. A smoke detector processing circuit based on the considered smoke sensor sensing element is proposed. It is shown that such a smoke detector is able to operate reliably under low concentration of smoke and high relative humidity conditions.

Tin dioxide thin film hydrogen nanosensor

We present the results of investigations of double-layer thin-film hydrogen sensors that show high sensitivity at low operating temperatures and improved reliability. These hydrogen sensors are manufactured using the both ion-plasma assisted sputtering and sol-gel technique. It was established that the highest sensitivity of the sensors occurred at 100-130°C. The hydrogen sensitivity depends on hydrogen concentration linearly starting at 50 ppm, and reaches 104 at 5000 ppm. The response time was 1-2 s and the recovery times were less than 10 s. We show that compared to constant power supply, pulse heating of the sensor improves the stability of the sensor, reduces the sensitivity to humidity, and reduces performance drift. Various possibilities of reducing CO gas cross sensitivity are also presented.

Determination of basic parameters of porous silicon

A new simple nondestructive capacitance method is proposed for determination of the basic parameters of porous silicon such as layer thickness, porosity and dielectric permittivity. The method is based on two measurements of the capacitance of a metal/porous silicon/single crystalline silicon/metal (M/PS/c-Si/M) structure, one measurement being performed with empty pores, and the other measurement with pores filled by an organic compound with a high value of dielectric permittivity. A comparison of results obtained by the ball lap and gravimetric techniques before and after anodization with the capacitance data measurements carried out with the same samples prior to their destruction shows sufficiently good agreement.

P1.7.10 Methanol and ethanol vapor sensitivity of MWCNT/SnO2/Ru nanocomposite structures

Multi-walled carbon nanotubes (MWCNTs) were successfully coated with tin-dioxide (SnO2) nanoparticles using both hydrothermal process and sol-gel technique under different solvent conditions. The obtained MWCNTs/SnO2 nanocomposites had the mass ratio of the components 1:4, 1:8 and 1:50, respectively. The as-prepared nanocomposites were characterized in detail using scanning electron microscopy (SEM) and X-ray powder diffraction (XRD) technique. On the base of these materials gas-sensor structures are developed. The high sensitivity to methanol and ethanol vapour as well as i-butane gas at 200 o C operation temperature have been revealed for the functionalized with Ru nanocomposite thick-film sensor structures having the ratio of the components 1:8 and 1:50. The structures with 1:4 ratio of the components are characterized by the best selectivity towards influence of methanol and ethanol vapor.

P1.0.12 Influence of applied voltage and catalyst layer thickness on SnO2 hydrogen sensor performance

The new version of sol-gel derived SnO2 thin-film hydrogen sensor operating at about two times lower temperature and, respectively, with lower consumed power have been obtained. Besides, relatively low resistance of the sensors resulting due to determination of the Pt catalyst layer optimal thickness allows reliable operation at low bias voltage which promotes stable operation even at high relative humidity conditions. In the present work we have examined changes of the sol-gel derived thin-film hydrogen sensors characteristics with increasing the Pt catalyst layer thickness up to 30 nm. It is shown that many parameters of gas sensors such as consumed power, long-term stability as well as selectivity are improved.