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    Design of a monitoring system for the identification of gas concentration in the district of Mi Perú - Callao, Perú
    (IJETAE Publication House, 2022-01-01)
    In recent years, the contamination of toxic gases in society is a very controversial problem because of the various consequences and effects they generate on health. There are several studies which highlight that the main polluting gases to the environment such as carbon monoxide, lead, cadmium, among others are the main causes of the increase in various acute diseases, such as pneumonia, or chronic diseases, such as cardiovascular diseases or lung cancer. That is why, faced with this problem, this research work proposes a monitoring system that determines the concentration of toxic gases, in such a way that it can contribute as an informative medium which can be implemented in various focused points where high rates of pollution are concentrated. The system has a very efficient MQ 135 gas sensor which includes a reading of 5 to 600 ppm (parts per million) at 3m with a temperature of 25ºC. It should be noted that it is important to keep the sensor on 24 hours beforehand to obtain a correct reading. Thus, concluding that this system of toxic gases can be easily applied to society because it is economical and because it has a free software which will be responsible for informing through a web server the level of ppm that you want to analyze at a certain point. Keywords- Toxic Gases, Pollution, Gas Sensor, Environment, Air Quality
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    Engineering dynamic defect compensation in Sn-Doped In2O3 thin films for enhanced optoelectronic performance
    (Elsevier BV, 2026-07-15)
    Sn-doped In2O3 is a typical transparent conducting oxide, yet the mechanisms governing carrier suppression and functional degradation at high doping levels remain unclear. Here, defect engineering via controlled Sn incorporation is employed to tune dynamic defect compensation, enabling direct correlation between defect chemistry and optoelectronic functionality. A non-monotonic evolution of lattice parameter and carrier density reveals two distinct regimes. At low Sn concentrations, enhanced free-electron density induces a Burstein–Moss bandgap widening. Beyond a critical doping threshold, cooperative compensation mediated by Sn4+/Sn2+ coexistence and oxygen interstitials suppresses carrier density, activating competition between bandgap renormalization and the Burstein–Moss shift. Density functional theory calculations confirm the electronic impact of this defect complex. Remarkably, the evolution of photocurrent closely mirrors the methane sensing response, demonstrating that oxygen-related defects regulate charge-transfer dynamics. These findings establish dynamic defect compensation as a tunable design principle for engineering multifunctional transparent conducting oxides.
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    Effect of the working pressure on the structural, morphological, optical, electrical and gas sensor properties of ZnO films grown by DC magnetron sputtering
    (Elsevier BV, 2026-02-01)
    In this work, ZnO thin films were deposited by DC magnetron sputtering under varying working pressures and subsequently annealed in air, followed by vacuum thermal annealing. The increase of working pressure drive to the reduction of the film thickness, crystallite size, lattice constants, and to the strengthening of the (002) X-ray diffraction peak, suggesting changes in the in oxygen vacancy concentration. Scanning electron microscopy revealed the formation of randomly distributed nanorods, while UV–Vis spectroscopy data analysis evidenced the presence of defect-related levels inside the band gap. As the thickness decreases, Hall measurements show a noticeable drop in charge carrier density and mobility, which is linked to the combined impact of defects and the decreasing size of crystallites. This suggests that thicker films exhibited a higher density of zinc interstitials, whereas thinner films exhibit more oxygen vacancies (VO[jls-end-space/]), mainly associated with surface states, as supported by temperature-dependent resistance measurements and photocurrent analysis. Gas detection tests demonstrated a superior response to methane (CH4[jls-end-space/]) for thinner films at 200 °C, attributed to their higher oxygen vacancy concentration. Photocurrent and gas sensing measurements showed similar trends, indicating a common defect-driven mechanism. These results highlight the potential of tuning defect chemistry in ZnO films to optimize their performance for gas sensing and optoelectronic devices.
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