In this paper, we investigated the optical and thermo-optical properties of a-SiN_x:H layers obtained using the PECVD technique. SiN_x:H layers with different refractive indices were obtained from silane and ammonia as precursor gases. Surface morphology and chemical composition studies were investigated using atomic force microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy and energy dispersive spectrometry methods. Spectroscopic ellipsometry was used to determine the optical indexes, thicknesses and optical bandgap of the films. The main purpose was to identify the thermo-optical characteristics of layers with different refractive indexes. Thermo-optical studies were performed to determine the temperature hysteresis of optical parameters. These measurements showed that after annealing up to 300 °C and subsequent cooling, the value of optical parameters returned to the initial values.

Controlling environmental pollution is a burning problem for all countries more than ever. Currently, due to the increasing industrialization, the number of days when the limits of air pollutants are over the threshold levels exceeds 80–85% of the year. Therefore, cheap and effective sensors are always welcome. One idea is to combine such solutions with cars and provide real-time information about the current pollution level. However, the environmental conditions are demanding, and thus the developed sensors need to be characterized by the high 3S parameters: sensitivity, stability and selectivity. In this paper, we present the results on the heterostructure of CuO/SnO_x and SnO_x/CuO as a possible approach for selective NO₂ detection. The developed gas sensors exhibited lower operating temperature and high response in the wide range of NO₂ and in a wide range of relative humidity changes. Material characterizations and impedance spectroscopy measurements were also conducted to analyze the chemical and electrical behavior.

In this work, the results of ellipsometric studies of thin films of broadband oxides (ZnO, TiO₂, ZrO₂) and broadband oxides doped with Al₂O₃ (Al₂O₃–ZnO, Al₂O₃–TiO₂, Al₂O₃–ZrO₂) are presented. All layers have been produced using the atomic layer deposition method. Ellipsometric studies were performed in the wavelength range of 193–1690 nm. Sellmeier and Cauchy models were used to describe the optical properties of the tested layers. Dispersion dependencies of refractive indices were determined for thin layers of broadband oxides on silicon substrates, and then for layers of Al₂O₃ admixture. The EDX investigations enabled estimation of the composition of the alloys. The Bruggeman effective medium approximation (EMA) model was used to determine the theoretical dependencies of the dispersion refractive indices of the studied alloys. The refractive index values determined using the Bruggeman EMA model are in good agreement with the values determined from the ellipsometric measurements. The doping of thin layers of ZnO, ZrO₂ and TiO₂ with Al₂O₃ enables the creation of anti-reflective layers and filters with a specific refractive index.

Optical and thermo-optical studies of hydrogenated amorphous silicon-rich nitride films were carried out. The films were produced by plasma-assisted chemical vapor deposition on glass. It is shown that the films deposited under appropriately selected processing conditions contain little nitrogen, as confirmed by Fourier-transform infrared spectroscopy therefore they are referred to as silicon-rich nitrides, a-SRN:H. Spectroscopic ellipsometry, reflectance, and transmittance spectroscopy were used to determine the optical indexes of the films and their thicknesses. It results from the ellipsometric measurements performed within a 190-1700nm spectral wavelength range that a-SRN:H films exhibit a high refractive index of about 3.7. It is also shown that post-deposition annealing up to 300°C does not affect the optical parameters of the films. Additionally, they are transparent in the near-infrared region, which makes them a good candidate for applications in various optoelectronic systems.