Wide-Range Band-Gap Tuning and High Electrical Conductivity in La- and Pb-Doped SrSnO3 Epitaxial Films

Impurity Level-Induced Broadband Photoelectric Response in Wide-Bandgap Semiconductor SrSnO3

Broadband spectrum detectors exhibit great promise in fields such as multispectral imaging and optical communications. Despite significant progress, challenges like materials instability in such devices, complex manufacturing process, and high cost still hinder their further application. Here, we present a method that achieves broadband spectral detection by impurity-level in SrSnO3. We report over 500 mA/W photoresponsivity at 275 nm (ultraviolet C solar-bind) and 367 nm (ultraviolet A) and ∼60 mA/W photoresponsivity at 532 and 700 nm (visible) with a voltage bias of -5 V. Further transport and photoluminescence results reveal a new phase transition at 88 K, which would significantly affect the impurity level of the La-doped SrSnO3 film, indicating that the broadband response attributes to the impurity levels and mutual interactions. Additionally, the photodetector demonstrates excellent robustness and stability under repeated tests and prolonged exposure in air. These findings show the potential of SrSnO3 as a material for photodetectors and propose a method to achieve broadband spectrum detection, creating new possibility for the development of single-phase, low-cost, simple structure, and high-efficiency photodetectors.

First-principles prediction of half metallic-ferromagnetism in La0.25Sr0.75Sn0.4In0.25Ru0.35O3 and enhanced experimental electrical and magnetic behaviours

A successful mechanochemical synthesis of a new nanoscale semi-conductive perovskite, La0.25Sr0.75Sn0.4In0.25Ru0.35O3 (LSSIRuO) was achieved through co-doping of SrSnO3. XRD and IR analyses confirmed that the sample crystallized in a pure perovskite GdFeO3 type structure (Pnma space group). Diffuse reflectance measurements revealed a direct band gap of 1.3 eV, which was significantly narrowed compared to that of SrSnO3 (4.1 eV). The investigation of DFT calculations into the sextenary systems La0.25Sr0.75[Sn0.4Ru0.35]In0.25O3 and La0.25Sr0.75[Sn0.5Ru0.25]In0.25O3 has revealed semiconductor behavior, very close to a semiconductor-semi metal transition. Importantly, Arrhenius-type charge transport was confirmed through a temperature-dependent conductivity study of the sample, showing good electrical conductivity of 3.6 S m-1 at 513 K with an activation energy of Ea = 0.19 eV. Furthermore, the compound exhibited ferromagnetic ordering at temperatures lower than 155 K, contrasting the diamagnetic behavior of SrSnO3. The narrower band gap value (1.3 eV) and improved electrical properties of LSSIRuO, in addition to its ferromagnetic characteristics, distinguish it as a promising candidate for applications in optoelectronics, as well as in memory and spintronic devices.

Pb/Pb3O4 Metal-Semiconductor Nanocomposite Obtained on 4A Zeolite-Optical and Structural Properties

This work describes a controlled and low-cost synthesis method to obtain Pb/Pb3O4 nanocomposites using synthetic zeolite 4A. The nanostructures obtained have a core-shell configuration with 5-25 nm diameters. High-resolution transmission electron microscopy (HRTEM), BF, high-angle annular dark-field annular scanning transmission electron microscopy (HAADF-STEM), energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and ultraviolet-visible (UV-vis) characterization techniques were used. Crystallographic planes (111), (200), and (220) for the core and planes (110) and (211) for the shell, corresponding to FCC and tetragonal structures for Pb and Pb3O4, respectively, were determined using HRTEM. The HAADF-STEM images allowed the analysis of intensity contrast images proportional to the number of atoms. XPS spectral analysis showed a 4.8 eV difference in binding energy between Pb 4f7/2 and Pb 4f5/2 for lead and lead oxide. EDS elemental mapping, XPS, and UV-vis spectroscopy analyses revealed the simultaneous presence of lead and lead oxide in the same structure. The band gap obtained for the shell was determined to be 4.50 eV. Consequently, Pb/Pb3O4 nanocomposites show a higher response to high-energy photons, making them suitable for UV photocatalysis applications.

Deep-UV Transparent Conducting Oxide La-Doped SrSnO3 with a High Figure of Merit

Perovskite stannate SrSnO₃ (SSO) is attracting attention as ultraviolet transparent conducting oxides (UV TCOs) due to its ultrawide band gap and high conductivity. Here, we investigate in detail the thickness-dependent electrical, structural, and optical properties of sequentially strain-relaxed La-doped SrSnO₃ (SLSO) epitaxial thin films. We find that the SLSO films grow as an orthorhombic Pnma phase with a ^- a ^- c ⁺ in the c ⁺ direction under the tensile strain. With the strain relaxation, as the films become thicker, vertical grain boundaries are created and the orthorhombic phase becomes reoriented to all three possible orientations. Simultaneously, the conductance starts to deviate from the linear behavior with increasing film thickness. Through the analysis of thickness fringes in optical transmittance, we found that a 120 nm thick nominally 4% La-doped SrSnO₃ film has a figure of merit (φ_TC = 2.65 × 10^-3 Ω^-1) at λ = 300 nm in the deep-UV region, which is the highest value among the well-known candidates for UV TCOs reported to date.

Evaluating the Band Gaps of Semiconductors by Cataluminescence

A rapid and efficient methodology for the evaluation of band gaps of semiconductors is highly desirable to analyze and assess the intrinsic properties and extending application scopes of semiconductor materials. Here, the negative correlation of the cataluminescence (CTL) signal in the presence of H₂S and the band gap of Aurivillius-type perovskite oxide Bi_4+nFe_nTi₃O_12+3n (n = 1-4) was confirmed, where the H₂S-induced CTL signal acts as a probe to evaluate the band gaps of semiconductor materials. The related mechanism shows that the thermal energy obtained by heating makes the electrons in the valence band more easily excite into the conduction band of a narrower band gap material and further promotes electron transfer between the gaseous compounds and semiconductor materials, causing acceleration of the catalytic oxide process. In addition, the extensibility was further verified by exploring the layered perovskite containing other insertion structures, including Bi_4+nCo_nTi₃O_12+3n (n = 1-4), Bi₅NiTi₃O₁₅, and Bi₅MnTi₃O₁₅, which was also consistent with the results characterized by UV diffuse reflectance spectroscopy. The established CTL probe for band gap evaluation shows rapid response, is simple to operate, and is of low cost, which is expected to become an innovative alternative to the conventional band gap assessment approach.