Influence of Al Doping on the Morphological, Structural and Gas Sensing Properties of Electrochemically Deposited ZnO Films on Quartz Resonators

The detection of hazardous gases at different concentration levels at low and room temperature is still an actual and challenging task. In this paper, Al-doped ZnO thin films are synthesized by the electrochemical deposition method on the gold electrodes of AT-cut quartz resonators, vibrating at 10 MHz. The average roughness, surface morphology and gas sensing properties are investigated. The average roughness of Al-doped ZnO layers strongly depends on the amount of the doping agent Al2(SO4)3 added to the solution. The structural dependence of these films with varying Al concentrations is evident from the scanning electron microscopy images. The sensing properties to ethanol and ammonia analytes were tested in the range of 0–12,800 ppm. In the analysis of the sensitivity to ammonia, a dependence on the concentration of the added Al2(SO4)3 in the electrochemically deposited layers is also observed, as the most sensitive layer is at 3 × 10−5 M. The sensitivity and the detection limit in case of ammonia are, respectively, 0.03 Hz/ppm and 100 ppm for the optimal doping concentration. The sensitivity depends on the active surface area of the layers, with those with a more developed surface being more sensitive. Al-doped ZnO layers showed a good long-term stability and reproducibility towards ammonia and ethanol gases. In the case of ethanol, the sensitivity is an order lower than that for ammonia, as those deposited with Al2(SO4)3 do not practically react to ethanol.

SENSORY FEATURES OF TIACALIXARENE FILMS TOWARDS TOXIC AND EXPLOSIVE VOLETILE COMPOUNDS

The work is dedicated to the investigation of adsorption features of functionalized derivatives of tiacalix[4]arenes towards phosphorus and chlorine organic volatile compound as well as well as to nitroaromatic simulators of explosive organic compounds. Experiments were carried out with quartz resonators array covered with the films of calixarene receptors. Experiments were performed at the concentration levels 10–1000 ppm, that corresponds to 100–10 dilution of the saturated vapours of analytes. Detection limits reached 10–100 ppm depending on the type of analyzed toxic substances; operational speed was about 10–20 sec.

Влияние освещения на пьезоэлектрические характеристики кварцевых резонаторов

The results of the effect of lighting on the piezoelectric characteristics of quartz resonators in the form of a tuning fork, which have been pre-trained by increased friction from the external environment, are presented. A significant change in the piezoelectric characteristics of such resonators was found depending on the intensity and spectrum of illumination. It is assumed that the detected change in the characteristics of the resonators is due to dislocations formed in the resonator during training with increased friction of the external environment, and is a manifestation of the well-known photoplastic effect and its quenching.

ANALYSES OF OSCILLATION PHASE NOISE BASIC ON CALCULATIONS OF MAXIMUM EXITATON LEVEL DIFFERENT CRYSTAL CUTS

This paper discuss the method of determining the lower limit of noise crystal oscillator and the calculation of the noise for some common types of quartz resonators. The calculations make choise of optimal constructions of crystal.

Finite-Element Simulation of the Eigen Frequency Spectrum of the Cylindrical Resonator with Geometrical Imperfectness

The solid-state wave gyroscope belongs to the class of the so-called Coriolis vibratory gyroscopes. They are industrially produced, as a rule, in two versions: precise solid-state wave gyroscopes with expensive fused quartz resonators, and devices of low accuracy with metal resonators. The use of metal for the manufacture of a solid-state wave gyroscope resonator for inertial systems of medium and low accuracy can significantly simplify the design of the device and reduce its cost, however, the low-quality factor of the metal resonator and the instability of its dissipative characteristics limit the accuracy characteristics of the solid-state wave gyroscope. The use of high-quality precision fused quartz glass resonators in such solid-state wave gyroscopes is unacceptable because of their high cost. The purpose of the work is to study the characteristics of inexpensive quartz resonators made from industrially produced fused quartz tubes, with the aim of creating a medium-accuracy solid-state wave gyroscope. Using the finite element method, the main types of geometric heterogeneities arising from the production of such resonators and their influence on their spectral characteristics are investigated. The experimental results allow us to draw conclusions about the most significant defects affecting the performance and accuracy of the solid-state wave gyroscopes