## 4 Conclusions  
UV photodetectors based on \(n\)-TiO\({}_{2}\) and a \(p\)-CuMnO\({}_{2}\) heterojunction were successfully obtained via a simple, reproducible and inexpensive method following two steps. Firstly, the TiO\({}_{2}\) layers were grown on Ti foil by thermal oxidation (Ti-TiO\({}_{2}\)), afterwards the CuMnO\({}_{2}\) films were deposited onto the surface of the TiO\({}_{2}\) layers by the Doctor Blade method. The structural characteristics of the Ti-TiO\({}_{2}\) layers and Ti-TiO\({}_{2}\)-CuMnO\({}_{2}\) sensors were investigated by XRD technique, which confirmed the phases' stability and purity of the as-synthesized materials. Morphological characteristics that were determined by SEM and AFM underlined that the TiO\({}_{2}\) layers were grown and oriented in clearly defined and delimited directions by the curved surfaces of the polyhedral structure. The CuMnO\({}_{2}\) films uniformly covered, without cracks, the surface of the TiO\({}_{2}\) layers following their polyhedral shape. From the AFM analysis, it was observed that the treatment times of Ti foils in HF solution influences the particle size and thickness of the TiO\({}_{2}\) layer. As the corrosion time increases, the particle size decreases, and the layer thickness increases. The thickness and the roughness of the TiO\({}_{2}\) layer directly influence the opto-electrical characteristics of the sensors. From the Mott-Schottky measurements, it was observed that the flat-band potential \(V_{FB}\) and the carrier densities (linear increase) for TiO\({}_{2}\) are influenced by the layer thickness. It was also observed that there is a correlation between the evolution of the flat band and the sensitivity of the sensors, which is better represented by S1a and S2a than S3a. The electrical parameters of the \(n\)-TiO\({}_{2}\)/\(p\)-CuMnO\({}_{2}\) heterojunction in the dark and UV illumination conditions highlighted that the minimum voltage of the junction, which is the voltage necessary for starting the conduction of current in the forward direction (turn-on voltage), increases according to structure of the Ti-TiO\({}_{2}\) layers. Thus, sensor S3a had the highest voltage values, which in the dark state was about 1.310 V, and in UV conditions was about 0.812 V. Also, a close correlation between the ideality factor and the sensibility in UV illumination have been established. The sensor S2a displays a sensibility value of 4.99, a responsivity of 100.6 mA mW\({}^{-1}\) cm\({}^{2}\), and a high-speed response time of about 1.56 s. A decrease in the grain size (to approx. 25 nm) leads to a decrease in the structural stability of the junction and has an undesirable effect on the temporal stability of the sensor. The UV-Vis rejection ratios were determined by illumination in the Vis spectrum, and the obtained results show that the sensor acts as a suitable selective UV photodetector. In conclusion, the method of thermal oxidation that was used for obtaining the \"_n_\" component (Ti-TiO\({}_{2}\)) of the heterojunction provides a simple choice for the achievement of oxide layers with suitable structures for the development of UV sensors (Ti-TiO\({}_{2}\)-CuMnO\({}_{2}\)). The results show that the UV photodetectors that are based on the _n_-TiO\({}_{2}\)/_p_-CuMnO\({}_{2}\) heterojunction and obtained through a new approach have great potential applications in light detection systems. [PERSON] was involved in methodology, investigation, writing--original draft; [PERSON] was involved in methodology, investigation, writing--original draft, [PERSON] was involved in methodology, investigation, writing--original draft; [PERSON] was involved in validation, investigation, writing--original draft, [PERSON] was involved in conceptualization, methodology, validation, investigation, writing--original draft, supervision; [PERSON] was involved in writing and editing of the original draft; All authors have read and agreed to the published version of the manuscript.