Self-powered UV sensing has enormous potential in military and civilian applications. However, achieving high responsivity and fast response/recovery time presents significant challenges. Self-powered photodetectors (PDs) have several advantages over traditional PDs, including higher sensitivity, lower power consumption, and simpler design. This study introduces a breakthrough self-powered PD that uses a Schottky junction of 2D α-MoO₃/iridium (Ir)/Si ultrathin film to detect 365 nm light at 0 V bias through using atomic layer deposition (ALD) and sputtering systems. The PD response is enhanced by plasmonic Ir-induced hot carriers, enabling detection in a mere 0.1 ms. Incorporating a 4 nm Ir layer boosts the responsivity from 0 to 34 A W⁻¹, and the external quantum efficiency is elevated from 0 to 7E11 under 365 nm light illumination. It also has a high I_ON/I_OFF ratio of 11.22E4 at 0 V. These results make the MoO₃/4 nm Ir/Si structure an interesting option for self-powered PDs with high efficiency, and the use of a simple ALD system for large-scale fabrication of 2D α-MoO₃ on hot carrier Ir plasmonic layer. The findings of this research hold tremendous promise in the field of UV sensing and can lead to exciting developments in military and civilian technology.

Photonic crystal (PhC) has been studied for their potential to improve the efficiency of Cu₂ZnSnS₄ solar cells by increasing the generated photocurrent by integrating it as a back reflector with almost zero transmission through the absorption active zone of the solar cell. It was found that the thickness of PhC layers greatly affects the width of the photonic bandgap and that increasing the thickness of VO₂ causes it to shift to a higher wavelength range. The PhC layers were added at the back side of the solar cell in two different configurations: (Monoclinic (M) VO₂/TiO₂) and (Tetragonal (T) VO₂/TiO₂) via SCAPS model. The study found that the (M VO₂/TiO₂) configuration led to an enhancement of the device's efficiency from 11.02 to 12.79%, while the (T VO₂/TiO₂) reaches 16.88%. The study concluded that the PhC layers enhance the light-matter coupling and photonic coupling and improvement in the device's performance.

To study the structural, electronic, and optical properties of lead-free Barium titanate BaTiO₃ (BT) ferroelectric material in its tetragonal structure, a combination of experimental and theoretical studies has been used and the obtained results were discussed. The studied BT compound was prepared via the sol–gel technique. The calculated bandgap energy (E_g) and structural parameters of BT are determined using four types of exchange–correlation functionals (PBE, PBEsol, LDA, and PW91) in the perspective of the density functional theory (DFT). XRD and Raman analysis have shown that BT ceramic exhibits a tetragonal phase structure without any trace of impurity phases. The UV–vis investigation showed that BT has a bandgap energy of 3.19 eV, which is larger than the theoretically calculated values. The computed lattice parameter c is overestimated (as large as ~1% deviation) when using the LDA approximation. In contrast, PBEsol proved that those lattice constants were close to the experimental values (a deviation of less than 1%).

This study was on the optoelectronic properties of multilayered two-dimensional MoS₂ and WS₂ materials on a silicon substrate using sputtering physical vapor deposition (PVD) and chemical vapor deposition (CVD) techniques. For the first time, we report ultraviolet (UV) photoresponses under air, CO₂, and O₂ environments at different flow rates. The electrical Hall effect measurement showed the existence of MoS₂ (n-type)/Si (p-type) and WS₂ (P-type)/Si (p-type) heterojunctions with a higher sheet carrier concentration of 5.50 × 10⁵ cm⁻² for WS₂ thin film. The IV electrical results revealed that WS₂ is more reactive than MoS₂ film under different gas stimuli. WS₂ film showed high stability under different bias voltages, even at zero bias voltage, due to the noticeably good carrier mobility of 29.8 × 10² cm²/V. WS₂ film indicated a fast rise/decay time of 0.23/0.21 s under air while a faster response of 0.190/0.10 s under a CO₂ environment was observed. Additionally, the external quantum efficiency of WS₂ revealed a remarkable enhancement in the CO₂ environment of 1.62 × 10⁸ compared to MoS₂ film with 6.74 × 10⁶. According to our findings, the presence of CO₂ on the surface of WS₂ improves such optoelectronic properties as photocurrent gain, photoresponsivity, external quantum efficiency, and detectivity. These results indicate potential applications of WS₂ as a photodetector under gas stimuli for future optoelectronic applications.

Studying the mechanical properties mismatching of SnSe₂/ZrS₂ 2D materials with Voigt-Reuss-Hill (VRH) schemes promise a novel structure for sensing applications. For the first time, we studied the effect of mechanical mismatching properties of SnSe₂/ZrS₂ multilayers with VRH schemes on the acoustic wave's propagation through acoustic superlattice (AS). We proposed [(SnSe₂/ZrS₂)⁴] superlattice with VRH schemes as a new THz multichannel sensor for acetonitrile sensing. The [(SnSe₂/ZrS₂)⁴] with Voigt scheme introduced several resonant peaks for acetonitrile inside the superlattice bandgap compared to Hill and Reuss schemes. The appropriate relation between resonance frequency shift and resonance bandwidth is the key to improving the multichannel sensor's sensitivity to liquid characteristics. Further, we studied the effect of low and high temperatures on our multichannel sensor. Furthermore, the highest sensitivity and resonance frequency were recorded by our AS with the Voigt scheme towards acetonitrile having values of 0.287 (GHz/(kg/m³)) and 0.237 THz at 0 °C. The results show a novel sensitivity of acetonitrile for low-temperature environments.

Artificial periodic structures drew a lot of attention because of their ability to be built with novel acoustic features. A novel nanostructured phononic superlattice (NPhS) based two-dimensional multilayer structure as a high-sensitive multichannel liquid sensor that provided bright multichannel band gap windows has been introduced. Theoretically, the designed structure is composed of [(MoS₂/PtSe₂)⁴] NPhS with a cavity filled with different concentrations of Ethylene Glycol at room temperature toward acoustic bandgap engineering multichannel sensor. We examined the interaction of acoustic waves with nano and bulk phononic superlattice (PhS) structures. In addition, we studied the effect of using different analyte layer thicknesses on the resonance peaks that appeared inside the band gaps. Many sharp resonance peaks appeared in multi-band gaps, which introduced high sensitivity, Q-factor, and figure of merit (FOM) values for each concentration of Ethylene Glycol. Furthermore, the effect of resonance peaks' full width at half maximum (FWHM) on the Q-factor of the NPhS multichannel sensor has been studied. From our results, the relation between the sensitivity of our multichannel sensor and the resonance frequency of each concentration shows a linear behavior. The highest sensitivity was obtained for a 1.00 m% concentration of 0.21 (GHz/(kg/m³)) at a resonance frequency value of 0.21 THz. In addition, the NPhS multichannel sensor recorded the highest Q-factor for 0.8069 m% with a value of 1744 and the highest FOM for 0.3819 m% with a value of 0.05988 (m³/kg). Moreover, we studied the effect of temperature on the sensitivity of the NPhS multichannel sensor. We showed the highest sensitivity value of 1.79 (GHz/^o C) at 10 °C towards Ethylene Glycol. Further, the dispersion relation of an acoustic wave propagating inside perfect and defected nano and bulk PhS structures has been introduced. Our proposed multichannel liquid sensor can introduce a novel sensitivity at Terahertz frequency ranges.

The application of the photonic superlattice in advanced photonics has become a demanding field, especially for two-dimensional and strongly correlated oxides. Because it experiences an abrupt metal-insulator transition near ambient temperature, where the electrical resistivity varies by orders of magnitude, vanadium oxide (VO2) shows potential as a building block for infrared switching and sensing devices. We reported a first principle study of superlattice structures of VO2 as a strongly correlated phase transition material and tungsten diselenide (WSe2) as a two-dimensional transition metal dichalcogenide layer. Based on first-principles calculations, we exploit the effect of semiconductor monoclinic and metallic tetragonal state of VO2 with WSe2 in a photonic superlattices structure through the near and mid-infrared (NIR-MIR) thermochromic phase transition regions. By increasing the thickness of the VO2 layer, the photonic bandgap (PhB) gets red-shifted. We observed linear dependence of the PhB width on the VO2 thickness. For the monoclinic case of VO2, the number of the forbidden bands increase with the number of layers of WSe2. New forbidden gaps are preferred to appear at a slight angle of incidence, and the wider one can predominate at larger angles. We presented an efficient way to control the flow of the NIR-MIR in both summer and winter environments for phase transition and photonic thermochromic applications. This study's findings may help understand vanadium oxide's role in tunable photonic superlattice for infrared switchable devices and optical filters.