Copper-Containing Films Obtained by the Simple Citrate Sol–Gel Route for NO2 Detection: Adsorption and Kinetic Study

The citrate sol–gel method was utilized for the fabrication of copper-containing films sensitive to NO2 gas. Effect of annealing temperature on the film phase composition, morphology, and sensor response was studied. X-ray diffraction reveals the formation of Cu2Cl(OH)3 phase at 250 °C and the CuO phase at 350 and 500 °C. It was found out that the films annealed at 250 °C and 350 °C showed the best sensor characteristics. The influence of thermal degradation on the probability of percolation effect in films and its connection to a decrease of gas sensitivity was studied. The kinetics of the NO2 gas adsorption on the film’s surface was described following the Elovich model. Activation energy estimated from the ln(S) vs. 1/T plots was 252 and 30 kJ/mol for the films annealed at 250 and 350 °C, respectively

Electrochemical Deposition of Silicon-Carbon Films: A Study on the Nucleation and Growth Mechanism

Silicon-carbon films have been deposited on silicon and Al2O3/Cr-Cu substrates, making use of the electrolysis of methanol/dimethylformamide-hexamethyldisilazane (HMDS) solutions. The electrodeposited films were characterized by Raman spectroscopy and scanning electron microscopy, respectively. Moreover, the nucleation and growth mechanism of the films were studied from the experimental current transients

ВПЛИВ ТЕХНОЛОГІЧНИХ РЕЖИМІВ НА МОРФОЛОГІЮ ПОВЕРХНІ ПЛІВОК СКЛАДУ SіOx(SnOy)

The analysis of the SiOx(SnOy) film surface morphology was made. Influence of the aging process parameters on microstructure and surface morphology of the films, deposited from the investigated solutions, for gas sensor applications was shown. The process of film structure forming was studied from the point of self-organization theory. Проведен анализ морфологии поверхности пленок состава SiOx(SnOy). Показано влияние параметров созревания исходных пленкообразующих растворов на микроструктуру и морфологию поверхности. Изучены процессы формирования структуры пленок с позиции теории самоорганизации.Проведено аналіз морфології поверхні плівок складу SіOx(SnOy). Показано вплив параметрів дозрівання вихідних плівкоутворюючих розчинів на мікроструктуру та морфологію поверхні. Вивчено процеси формування структури плівок з позиції теорії самоорганізації

Comparative Analysis of Derivative Parameters of Chemoresistive Sensor Signals for Gas Concentration Estimation

Signals from resistive gas sensors based on zirconium dioxide and silicon–carbon films have been extensively investigated to estimate gas concentration. In this study, the change in the normalized resistance of the sensor’s response under NO2 exposure is shown and the analysis of the first and second derivatives of the response curves were carried out. A signal-processing scheme, reducing the effect of noise and signal drift, is proposed. The extreme of the second derivative of the sensor response, the initial reaction rate, and the slope of the curve of the approximating line in the coordinates of the Elovich equation are proposed as calibration dependencies. The calibration curves built from the values of the maximum second derivative turned out to be the most stable, with the lowest relative error in estimating gas concentration compared to the traditional fixed-time point method

Resistive Low-Temperature Sensor Based on the SiO₂ZrO₂ Film for Detection of High Concentrations of NO₂ Gas

The SiO2ZrO2 composite films were prepared by means of sol-gel technology and characterized by scanning electron microscopy, energy dispersive X-ray (EDX) analysis, and X-ray diffraction. The presence of the stable monoclinic ZrO2 with an impurity of tetragonal phases is shown. The film surface is characterized by the presence of ZrOCl2·6H2O or ZrCl(OH)/ZrCl(OH)2 grains. The crystallite size negligibly depends on the annealing temperature of the film and amount to 10⁻12 nm and 9⁻12 nm for the films thermally treated at 200 °C and 500 °C, respectively. The film’s resistance is rather sensitive to the presence of NO2 impurities in the air at a low operating temperature (25 °C). Accelerated stability tests of the initial resistance showed high stability and reproducibility of the sensor based on the SiO2ZrO2 film thermally treated at 500 °C

CuOx Films for NO2 Detection Microstructurel Characterization

Copper oxides films as promising materials for gas sensors applications were studied. Copper oxide films were deposited onto Si SiO2 substrates using a citrate sol gel method with the subsequent temperature treatment at 150 500 amp; 8304;C. These films were characterized by means of secondary electron microscopy SEM and X ray absorption near edge structure XANES spectroscopy. The prepared films were utilized in NO2 sensors. The dependences of the NO2 response on the operating temperature and NO2 concentration 10 200 ppm were investigated. The maximum NO2 response was achieved for the film annealed at 250 amp; 8304;