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Two-dimensional (2D) heterostructures formed by van der Waals (vdW) interactions have attracted considerable attention in the fields of electronics and optoelectronics. The stacking order is not only an important method for regulating interlayer interactions, but also an intrinsic property specific to 2D vdW heterostructures. Herein, the GaS/XMoY (X/Y = S, Se, Te) vdW heterostructures are proposed by first-principles calculations. The effects of stacking order (namely, GaS/SMoSe, GaS/SeMoS, GaS/SeMoTe and GaS/TeMoSe) on the electronic properties, light absorption, and photocatalysis of the heterostructures are discussed in detail. We identify stacking order as a dominant pathway for interlayer interactions, and surmise that stacking order effectively regulates dipole moment, mechanical flexibility, carrier mobility, optical absorption coefficient, and photocatalytic water-splitting of GaS/XMoY heterostructures. The in-plane biaxial strain can make the energy gap of each stacking order reach a maximum value, and their photocatalytic performance can also be improved to different degrees. This work analyzes the modulation effect of stacking order on the material properties of GaS/XMoY heterostructures, which provides theoretical clues for the design of efficient and stable optoelectronic devices and photocatalytic water-splitting. [ABSTRACT FROM AUTHOR]

In this work, Pr3+ ion‐doped Ge20Ga15−xSbxSe65 (x = 0, 5, 10, in mol%), Ge20Sb15−yInySe65 (y = 5, 10, in mol%), Ge20Ga15−zInzSe65 (z = 0, 5, 10, in mol%), and Ge20Ga5Sb10Se60I5 glasses were prepared. The structural units, thermal properties, and optical properties of these glasses were analyzed. In addition, a comprehensive comparison study of the effects of metal ions (Sb, Ga, and In), S/Se ratio, and I content on the mid‐infrared (MIR) luminescence of Pr3+ ions was conducted. Under a 1.55‐μm laser pump, 0.2 mol% of Pr3+ ion‐doped chalcogenide glasses performed strong photoluminescence in the wavelength range of 3.5‐5.5 μm. Results indicated that the Sb‐containing glass performed the strongest emission intensity among the studied glasses. Moreover, halogen element I can reduce the phonon energy of the matrix, which is beneficial to the luminescence of Pr3+ ions and provide significant possibilities for developing MIR lasers and amplifiers. [ABSTRACT FROM AUTHOR]

Abstract In this research, the optical properties of Er3+/Yb3+ co-doped phosphate glass have been studied to explore the potential of this glass system in laser and electronic amplifiers. The Judd–Ofelt (J-O) intensity parameter (Ω t) in the J-O model was established to determine the absorption intensity of the glass. The optical properties of the glass can be evaluated by various radiation parameters such as the radiative transition probabilities (A rad), stimulated emission cross sections (σ e), branching ratios (β JJ'), maximum half-width values (Δ λ p), and the radiation lifetime (τ rad) of the glass. It was found that in the case of Yb3+ as a sensitizer, the spectral properties of the Er3+ doped glass can be maximized. The data of A rad , β JJ' , τ rad , σ e and Δ λ p obtained by Er3+/Yb3+ co-doping can find that the Er3+-doped sample undergoes 4I 13/2 –4I 15/2 transition at 1.56 µm, and the stimulated emission cross section is greatly improved. The application prospects of the glass in solid near-infrared laser and electronic communication was discussed. According to the comprehensive discussion and analysis, the glass has great application potential. [ABSTRACT FROM AUTHOR]

Hydrogenated amorphous carbon (a-C:H) thin films are deposited by plasma-enhanced chemical vapor deposition (PE-CVD) technique with different frequency (RF) powers at a low substrate temperature (fixed at 250 °C). In this work, the composition, the types of chemical banding, carbon hybridization structure and optical properties of the a-C:H thin films have been studied by FTIR, XPS, UV–Vis spectrum and PL spectrum testing techniques. The results show that the hydrogen content and carbon hybridization structure play an important role in the evolution of photoluminescence (PL) properties with increasing RF power. It is found that with the decrease of sp 3 /sp 2 ratio, the peak energy for main PL emissions peaks (mode 2) showed a red shift. PL emission intensity of the a-C:H thin films is influenced by the hydrogen content and carbon sp 2 cluster. The enlargement of sp 2 rich clusters and the increase of the hydrogen content will lead to an enhancement of PL emission intensity, which is a consequence that the domain of sp 2 rich clusters creates more radiative recombination centers with the increase of RF power. Furthermore, different full width at half maximum (FWHM) of PL emissions peaks can be attributed to band-to-band recombination in various size sp 2 rich clusters. [ABSTRACT FROM AUTHOR]

Abstract In this work, hydrogenated amorphous carbon (a-C:H) films were prepared by using a radio frequency (13.56 MHz) plasma enhanced chemical vapor deposition (PECVD) method at 220 °C. The influence of the annealing treatments on the microstructure and optical properties of the a-C:H films has been investigated. Raman and X-ray photo electron spectroscopy (XPS) results showed that the sp2 carbon fraction and sp2/sp3 ratio increase and sp3 carbon fraction decrease with increasing the annealing temperature. However, with increasing annealing temperature, the D and G peak positions and the G peak FWHM have no obvious changes. The spectroscopic ellipsometry suggested that the density, refractive index n and the extinction coefficient k of the as-deposited film and the films annealed at 300 and 400 °C are not affected obviously by thermal annealing treatments. However, when the annealing temperature is higher than 400 °C, the films become high-density and opaque, meanwhile, the film thickness decrease significantly. The UV-VIS spectroscopy measurement indicated that the increase of sp2 fraction and graphitization features of the a-C: H films result in the decrease of the films transmission and optical band gap. Highlights • The correlation of optical properties with annealed a-C:H films structure is studied. • With increasing annealing temperature sp3 carbon transformed into sp2 carbon. • The D and G peak positions and the G peak FWHM have no obvious changes. • The density, n and k of the films are not affected at temperature <400 °C. [ABSTRACT FROM AUTHOR]

An Er 3+ /Yb 3+ co-doped bismuthate (Bi 2 O 3 -B 2 O 3 -CaO) glass was prepared by melt quenching method. The samples were analyzed by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), absorption and emission spectroscopy. The Judd-Ofelt parameters (Ω λ ) were determined from the intensity of the absorption band to calculate the radiation parameters, such as the radiation lifetime (τ rad ), radiation transition probability (A rad ) and branching ratio (β JJ′ ) of 4 I 13/2 laser conversion of Er 3+ ions. The effective emission bandwidth (Δλ P ), stimulated emission cross section (σ se ) and gain bandwidth (σ se × Δλ p ) were determined on the emission spectra, and the optimum doping concentration of Er 2 O 3 was 0.5 mol%. The present work indicates that Er 3+ /Yb 3+ co-doped bismuth calcium borate glass can be promising materials for solid state NIR lasers and fiber amplifiers. [ABSTRACT FROM AUTHOR]

The present GeTe 4 -AsTe 3 -AgI glasses extend the optical window to up to 25 μm and its glass-forming region has been explored for practical applications. Their structure, glass-forming ability, thermal stability, infrared transmitting properties were investigated. The results reveal that the GeTe 4 -AsTe 3 -AgI glasses exhibit a large glass-forming region situated around the GeTe 4 -rich domain. Raman analysis confirms the formed [GeTe 3 I] and [AsTe 2 I] units are mainly responsible for the improvement in glass-forming ability. The optimum 40GeTe 4 -30AsTe 3 -30AgI glasses exhibit a large optical window extending from 2 to 25 μm while being stable enough toward crystallization to permit the preparation of fibers and molded lenses. Under proper annealing at 150 °C, 40GeTe 4 -30AsTe 3 -30AgI glass-ceramics, with high mechanical and thermal properties while still keeping the IR transmittance unchanged, were obtained for the first time. [ABSTRACT FROM AUTHOR]