As—Te硫系膜的光学性质及其热致变化

利用真空射频溅射法制得了非晶态As-Te硫系薄膜。借助于XRD法研究了该系统薄膜的热致析晶,并与相应的块状样品作了比较。薄膜在热处理前后的光学折射率和消光系数分别进行了测定,分析了它们与薄膜组成、结构以及析出晶相的关系。另外还对薄膜随温度的变化过程进行了研究,指出了造成反射率发生变化的主要原因以及它们所对应的温度区域,对该系统薄膜在光盘方面的应用作了预言。     

具有芯皮结构的As—S玻璃红外光纤

设计制作了氩气加压的硬质玻璃双坩埚拉丝装置,可拉制不同丝径和芯皮比的As-S和其它硫系玻璃红外光纤。当采用As_(30)S_(62)作芯料,As_(35)S_(65)作皮料,制得光纤数值孔径为0.5,在2.4μm波长处损耗为1.32dB/m。As-S芯皮结构光纤比芯体玻璃拉制的裸光纤损耗小。     

Energy gap studies on As-Sb-Se glasses

Variation of optical energy gapE ₀ with composition in several glasses belonging to the As-Sb-Se system have been studied. The photoacoustic technique, well-suited for highly absorbing samples, has been used for the measurements. Results reported on the As _x Sb₅Se_95−x , As _x Sb₁₀Se_90−x , As _x Sb₁₅Se_85−x and As _x Sb₂₀Se_80−x glasses of the As-Sb-Se family are explained on the basis of the chemically ordered network model.     

Chalcogenide glasses as passive thin film structures for integrated optics

One approach to obtaining electro-optic or magneto-optic modulation in an integrated optic structure is to use a transparent film on an “active” (electro- or magneto-optic) optical substrate. Since the most useful active optical materials have relatively high refractive indices which preclude the use of oxide glasses as the transparent thin film, we have investigated the possibility of using higher index chalcogenide glasses in this configuration. Preliminary waveguiding studies were performed on a model system consisting of an As₂S₃ film on a LiNbO₃ substrate which demonstrated the feasibility of using chalcogenide glasses in this regard. The optical and mechanical properties of a suitable glass system, As-Ge-S, were then characterized. The characterization consisted of developing empirical formulas based on the type of bonding present in the glass which can be used to predict the relevant properties of a glass as a function of its composition. These formulas allow selection of optimum glass compositions to match a variety of electro-optic and magneto-optic substrates.     

Low gallium-content,dysprosium III-doped,Ge–As–Ga–Se chalcogenide glasses for active mid-infrared fiber optics

A systematic investigation is presented, for the first time, of a 1000 ppmw (parts per million, by weight) Dy³⁺-doped Ge–As–Ga–Se chalcogenide glass series, with a fixed low Ga content of 1 atomic% (at. %), suitable for active mid-infrared fiber optics. Seven glasses constitute the series, which have increasing average coordination number from 2.49 to 2.61, in steps of 0.02, with the GeSe₂, As₂Se₃, and Ga₂Se₃ stoichiometries kept. Glass formation is confirmed using X-ray diffraction and differential scanning calorimetry. Fourier transform infrared spectroscopy is reported for the series. Parallel plate viscometry enables prediction of fiber-drawing temperatures and, with differential thermal analysis, determines the potential for fiber fabrication. X-ray diffraction of samples after parallel-plate viscometry shows that Ge₂₅As₉Ga₁Se₆₅ (at. %) alone, in the glass-series, devitrifies to form the single-crystalline phase: monoclinic-GeSe₂; scanning electron microscope imaging suggests that this phase is both surface and bulk grown. Overall, the recommended host glass at. % compositions for doping with rare-earth ions and drawing to active mid-infrared fiber are: Ge_17.5As₁₈Ga₁Se_63.5, Ge₁₅As₂₁Ga₁Se₆₃, and Ge_12.5As₂₄Ga₁Se_62.5.     

Investigation of the Ga-Sb-S chalcogenide glass with low thermo-optic coefficient as an acousto-optic material

In this study, two series of Ga_xSb_40-xS₆₀ (x = 4, 6, 8, 10 mol%) and Ga_ySb₃₆S_64-y (y = 3, 5, 6 mol%) glasses were prepared and the relationship between their compositional and acousto-optic (AO) properties was investigated systematically for the first time. In the Ga_ySb₃₆S_64-y system, the AO figure of merit (M₂) increased as the Ga increased, and the maximum M₂ of the Ga₆Sb₃₆S₅₈ glass was 455.78 × 10^?18 s³/g, which is ～301 times greater than that of fused silica and ～2.5 times greater than that of As₂S₃ chalcogenide (ChG) glass at 1550 nm. However, its thermo-optic coefficients (dn/dT) varied greatly (32.1 × 10^?6 °C^?1–57.2 × 10^?6 °C^?1), and acoustic attenuations (α) at 10 MHz were high, from 5.446 dB/cm to 7.274 dB/cm. In the Ga_xSb_40-xS₆₀ glass system, the M₂ value and α at different ultrasonic frequencies gradually decreased with the improvement of Ga. Compared with the Ga_ySb₃₆S_64-y system, the Ga_xSb_40-xS₆₀ glass system had lower α (at 10 MHz) and dn/dT, which are 5.001 dB/cm–5.563 dB/cm and 17.3 × 10^?6 °C^?1–55.6 × 10^?6 °C^?1, respectively. These results provide a significant reference for the further development of novel ChG glasses and help expand their application fields.     

Solar hydrogen generation from organic substance using earth abundant CuS–NiO heterojunction semiconductor photocatalyst

This work explores the critical role of NiO co-catalyst assembled on the surface of a CuS primary photocatalyst which effectively improves interface properties and enhances solar-to-hydrogen production by prolonging lifetime of photo-excitons generated at the CuS surface. The nanoscale CuS/NiO heterojunction is formulated using hydrothermal and wet impregnation methods. The resultant CuS/NiO composite shows optical absorbance between 380 and 780 nm region. The type-II energetic structure formed at CuS/NiO heterojunction facilitates rapid charge separation and as a result, the CuS/NiO composite exhibits 13 folds higher photocatalytic water splitting performance than CuO and NiO. The champion CuO/NiO photocatalyst is first identified by screening the catalysts using a preliminary water splitting test reaction under natural Sunlight irradiation. After the optimization of the catalyst, it was further explored for enhanced photocatalytic hydrogen production using different organic substances dispersed in water (alcohols, amine and organic acids). The champion CuS/NiO catalyst (CPN-2) exhibited the photocatalytic hydrogen production rate of 52.3 mmol h^?1.g^?1_cat in the presence of lactic acid-based aqueous electrolyte and, it is superior than hydrogen production rate obtained in the presence of other organic substances (triethanolamine, glycerol, ethylene glycol, methanol) tested under identical experimental conditions. These results indicate that the energetic structure of CuS/NiO photocatalyst is favorable for photocatalytic oxidation or reforming of lactic acid. The oxidation of lactic acid contributes both protons and electrons for enhanced hydrogen generation as well as protects CuS from photocorrosion. The modification of surface property and energetic structure of CuS photocatalyst by the NiO co-catalyst improves photogenerated charge carrier separation and in turn enhances the solar-to-hydrogen generation efficiency. The recyclability tests showed the potential of CPN-2 photocatalyst for prolonged photocatalytic hydrogen production while continuous supply of lactic acid feedstock is available.     

氢诱导二维硫族化合物PtX2的电磁特性研究

为了充分研究二维重过渡金属硫族化合物材料在磁性器件中的潜在应用,基于自旋极化密度泛函理论,文中研究了氢化单层PtX₂(X=S,Se,Te)的稳定性和电磁特性。研究结果表明,单层PtX₂在氢化后具有较高的稳定性,且稳定性随硫族原子序数的增加而下降;氢化使单层PtX₂出现了磁矩,使其从半导体变为铁磁性的金属,该磁矩主要来自于窄反键子能带自旋极化下的Pt 5d电子。此外,单层PtX₂的铁磁性也随着硫族原子序数的增加而出现了下降的趋势。因此,文中的研究成果为设计二维重过渡金属硫族化合物材料的铁磁性提供了参考。     

Making BaZrS3 Chalcogenide Perovskite Thin Films by Molecular Beam Epitaxy

The making of BaZrS₃ thin films by molecular beam epitaxy (MBE) is demonstrated. BaZrS₃ forms in the orthorhombic distorted-perovskite structure with corner-sharing ZrS₆ octahedra. The single-step MBE process results in films smooth on the atomic scale, with near-perfect BaZrS₃ stoichiometry and an atomically sharp interface with the LaAlO₃ substrate. The films grow epitaxially via two competing growth modes: buffered epitaxy, with a self-assembled interface layer that relieves the epitaxial strain, and direct epitaxy, with rotated-cube-on-cube growth that accommodates the large lattice constant mismatch between the oxide and the sulfide perovskites. This work sets the stage for developing chalcogenide perovskites as a family of semiconductor alloys with properties that can be tuned with strain and composition in high-quality epitaxial thin films, as has been long-established for other systems including Si-Ge, III-Vs, and II-VIs. The methods demonstrated here also represent a revival of gas-source chalcogenide MBE.