The Effect of Production Parameters of Oxide Layers on Their Nanostructure, Nanomorphology, and Surface Free Energy

Self-Powered Photodetector Based on FTO/n-TiO2/p-CuMnO2 Transparent Thin Films

A self-powered photodetector with the FTO/n-TiO2/p-CuMnO2 configuration, representing the novelty of the work, was successfully achieved for the first time and presumes two steps: deposition of the n-type semiconductor (TiO2) by the doctor blade method and of the p-type semiconductor (CuMnO2) by the spin coating technique, respectively. Investigation techniques of the structural and morphological characteristics of the as-synthesized heterostructures, such as XRD, UV-VIS analysis, and SEM/EDX and AFM morphologies, were used. The I-t measurements of the photodetector showed that the responsivity in the self-powered mode was 2.84 × 107 A W−1 cm2 and in the 1 V bias mode it was 1.82 × 106 A W−1 cm2. Additionally, a self-powered current of 14.2 nA was generated under UV illumination with an intensity of 0.1 mW/cm2. Furthermore, under illumination conditions, the response time (tres) and the recovery time (trec) of the sensor exhibited a good response; thus, tres = 7.30 s and trec = 0.4 s for the self-powered mode, and in the 1 V bias mode, these were tres = 15.16 s and trec = 2.18 s. The above results show that the transparent heterojunction device of n-TiO2/p-CuMnO2 exhibited a self-powered ultraviolet photodetector with high sensitivity.

Nanostructure and Morphology of the Surface as Well as Micromechanical and Sclerometric Properties of Al2O3 Layers Subjected to Thermo-Chemical Treatment

The article presents the effect of the thermo-chemical treatment of Al₂O₃ layers on their nanostructure, surface morphology, chemical composition as well as their micromechanical and sclerometric properties. Oxide layers were produced on EN AW-5251 aluminium alloy (AlMg₂) by the method of direct current anodizing in a three-component electrolyte. The thermo-chemical treatment was carried out in distilled water and aqueous solutions of Na₂SO₄·10H₂O and Na₂Cr₂O₇·2H₂O. It was shown that the thermo-chemical treatment process changes the morphology of the surface of the layers (the formation of a sub-layer from the Na₂SO₄·10H₂O and Na₂Cr₂O₇·2H₂O solutions), which directly increases the thickness of the layers by 0.37 and 1.77 µm, respectively. The thermo-chemical treatment in water also resulted in the formation of a 0.63 µm thick sub-layer. The micromechanical tests indicated a rise in the surface microhardness of the layers in the case of their thermo-chemical treatment in water and the Na₂SO₄·10H₂O solution and a decrease in the case of the layers modified in the Na₂Cr₂O₇·2H₂O solution. The highest microhardness (7.1 GPa) was exhibited by the layer modified in the Na₂SO₄·10H₂O solution. Scratch tests demonstrated that the thermo-chemically treated layers had better adhesive properties than the reference layer. The best scratch resistance was exhibited by the layer after thermo-chemical treatment in the Na₂SO₄·10H₂O solution (the highest values, practically for all the critical loads) which, together with its low roughness and high load capacity, predispose it to sliding contacts.

Fabrication of a UV Photodetector Based on n-TiO2/p-CuMnO2 Heterostructures

The heterojunction based on n-TiO2 nanolayer/p-CuMnO2 thin film was achieved using an efficient two-step synthesis process for the fabrication of a UV photodetector. The first step consisted of obtaining the TiO2 nanolayer, which was grown on titan foil by thermal oxidation (Ti-TiO2). The second step consisted of CuMnO2 thin film deposition onto the surface of Ti-TiO2 using the Doctor Blade method. Techniques such as X-ray diffraction, UV-VIS analysis, SEM, and AFM morphologies were used for the investigation of the structural and morphological characteristics of the as-synthesized heterostructures. The Mott–Schottky analysis was performed in order to prove the n-TiO2/p-CuMnO2 junction. The I-V measurements of the n-TiO2 nanolayer/p-CuMnO2 thin film heterostructure confirm its diode characteristics under dark state, UV and visible illumination conditions. The obtained heterojunction, which is based on two types of semiconductors with different energy band structures, improves the separating results of charges, which is very important for high-performance UV photodetectors.

Influence of Anodizing Parameters on Surface Morphology and Surface-Free Energy of Al₂O₃ Layers Produced on EN AW-5251 Alloy

The paper presents the influence of the surface anodizing parameters of the aluminum alloy EN AW-5251 on the physicochemical properties of the oxide layers produced on it. Micrographs of the surface of the oxide layers were taken using a scanning electron microscope (SEM). The chemical composition of cross-sections from the oxide layers was studied using energy dispersive spectroscopy (EDS). The phase structure of the Al₂O₃ layers was determined by the pattern method using X-ray diffractometry (XRD). The nanomorphology of the oxide layers were analyzed based on microscopic photographs using the ImageJ 1.50i program. The energetic state of the layers was based on the surface-free energy (SFE), calculated from measurements of contact angles using the Owens-Wendt method. The highest surface-free energy value (49.12 mJ/m²) was recorded for the sample produced at 293 K, 3 A/dm², in 60 min. The lowest surface-free energy value (31.36 mJ/m²) was recorded for the sample produced at 283 K, 1 A/dm², in 20 min (the only hydrophobic layer). The highest average value nanopore area (2358.7 nm²) was recorded for the sample produced at 303 K, 4 A/dm², in 45 min. The lowest average value nanopore area (183 nm²) was recorded for the sample produced at 313 K, 1 A/dm², in 20 min.