Papers by Keyword: Reflectivity

Abstract: Three alternate TiN/AlN nanostructured multilayers with the TiN layer thicknesses of 60, 70, and 120 Å and the AlN layer thickness of 10 Å were fabricated using dc reactive magnetron sputtering. Microstructural characterizations of the three nano-scale films were performed using nonpolarized specular neutron reflectometry. The results showed that the three TiN/AlN multilayer thin films were typical superlattice films and the thicknesses of the TiN layer and AlN layer in the multilayers were consistent with the design thickness nearly. The interface roughness was asymmetric in all the samples. The interface of AlN growing on TiN was much sharper than that of TiN growing on AlN and the latter was the diffusion interface in the TiN/AlN multilayer films.

Abstract: Detection of organic materials or heavy ions using the surface plasmon resonance (SPR) effect of the MoS₂/Ag system was studies. We found that the reflectivity of the SPR system was sensitive to the incident angle of light, dielectric constant of the detected samples, wavelength of light, and thickness of the Ag film. It reached an extreme minimal value (EMV) at an extreme angle θ. As the dielectric constant of the samples was increased from 1.0 to 3.25, θ increased, enabling high-resolution detection. θ slightly decreased with the thickness of the Ag film changed from 300 to 700 nm for a given detected sample while the EMV of reflectivity increased. Moreover, the reflectivity curves were overlapped when the wavelength of light and the thickness, d of the Ag film both increased from 400 to 700 nm, showing synchronous effect. The results showed that MoS₂ was a suitable material for the detection of a wide range of samples and could replace the prism.

Abstract: La_1-xSrxTiO_3+δ (LST) has been studied in many fields due to its excellent physical and chemical properties. However, there are rare reports on its optical properties, especially reflectivity. Our previous work has prepared LST coatings by atmospheric plasma spraying technique, but the reflectivity is much lower than that of LST powder itself. In this paper, LST coating was prepared by knife coating which is a traditional convenient method. The phase structure and surface morphology of the coating were examined by X-ray diffraction and scanning electron microscopy, respectively. The optical property was characterized by UV-visible-near infrared spectroscopy and the laser ablation tests were carried out by YSL-2000 Fiber Laser (IPG Co) with the wavelength of 1070 nm and the spot size of 10 mm×10 mm. Results show that the reflectivity of the LST coatings depends on the weight ratio of LST and binder. A high-reflectivity coating can be prepared by knife coating with appropriate content of LST.

Abstract: Wave-absorbing coating samples are fabricated with ZnO whisker, the absorbent and silicon resin coating as the binder.The influences of the content of ZnO whisker in the absorbing coating and the thickness of the coating on millimeter wave absorbing property are analyzed.With the increasing of the thickness, the absorbing performance of the sample is enhanced significantly , the results show that with a ZnO whisker mass of 50% and coating thickness of 2 mm, excellent absorption (R<-10dB) is observed in the wave band from 66 to 78 GHz (with a bandwidth of 12GHz) . When the ZnO whisker mass is reduced to 30% with the same thickness of 2mm, two absorption bands are obtained from 55 to 67 GHz (with a bandwidth 12GHz) and 100 to 110 GHz (with a bandwidth 10GHz). Maxwell equations and boundary conditions are used to analyze the absorbing mechanism of the coating.

Abstract: MnAlFe alloy was prepared by the combined use of smelting, high-energy ball milling and tempering heat treatment process. The phase composition and microwave absorbing properties of MnAlFe alloy were investigated by X-ray diffractometer(XRD) and vector network analyzer. The results show that the powders consist of Al₈Mn₅ single phase with different Fe content; the dielectric loss and the magnetic loss increases with the addition of Fe, the resonant frequency and absorption peak of ε″ and μ″ moves towards lower frequency region simultaneously. The (Al₈Mn₅)₉₉Fe exhibits preferably comprehensive microwave absorbing properties in the range of 6-18 GHz. The value of the minimum reflectivity and absorption peak frequency with the coating thickness of 1.5 mm, are -23.1 dB, 15.04 GHz respectively. Owing to the wide applications of electromagnetic waves in the range of 1–4 GHz for mobile phone, local area network, radar systems and so on over the past few decades, the serious problems of the electromagnetic interference and electromagnetic compatibility have become increasingly prominent in recent years. Microwave absorbing materials, which possess special performance for absorbing electromagnetic wave, have been applied in both civil and military fields and play an important role in camouflage technology. In military field, stealth technology to reduce and eliminate the electromagnetic radiation and electromagnetic interference resulting from the broad applications of various kinds of electronic and microwave instruments, stealth technology plays an important strategic role in the wars in future[1-2]. The microwave absorbing materials can be used to reduce radar cross section for military use. For this reason, the microwave absorbing material is vitally important for both civil and military fields[3-7]. In view of this utilization, excellent microwave absorbing materials should exhibit strong microwave absorption properties over a wide frequency range and need to be thin and light in weight. It has an important meaning to the application of magnetic microwave absorbing materials. MnAl alloy can be used as microwave absorbent. It has properties such as light in weight, good thermal stability and corrosion resistance[8-11]. But as permanent magnets, MnAl has shortcomings such as their difficulties of fabrication and high costs that prevent them from being used as permanent magnets. A great value would be brought to either theory or practice through proper treatments as further improvement in properties. In this paper, we will discuss the effects of changing relative content of Fe on absorption properties of Al₈Mn₅ alloy.

Abstract: Ion-beam deposition of amorphous Ge layers on different substrates (silicon and quartz) has been performed. Deposited amorphous Ge layers were subjected to pulsed laser annealing (λ = 0.69 μm, τ = 80 ns). Simultaneously the optical probing of the Ge surface was carried out. The computer simulation of heating processes and phase transitions was performed taking into account the temperature dependences of film and substrates’ parameters and phase transition energies. The results of the dynamics of heating, melting, crystallization and plasma formation processes are well described by simulation data. It is shown that the threshold values for radiation power density and phase transition rates are determined mainly by thermophysical parameters of the substrates and thermal contact between Ge melt and substrate.

Abstract: We have theoretically and experimentally investigated the microcavity organic light-emitting diodes (MOLEDs) that enhanced the emission intensity and narrowed the spectra simultaneously. In this work, MOLEDs with the reflectivities of 70% and 90% have been successfully fabricated. Comparing to non-cavity OLEDs, the maximum forward electroluminescence intensity and the peak luminescence can be improved by 6.8 times and 2.2 times, respectively. The full width at half maximum could be sharply narrowed to 10 nm. The different configurations of MOLEDs with varied emitting layers have also been evaluated which fitted well with the experimental results.

Abstract: Double composite flexible absorbing fabrics were fabricated according to the resistance matching principle and electromagnetic spreading regulation. The surface layer, composed of stainless steel core-spun yarn, easily realized matching to the free space. The under layer made up of iron fiber which had significant microwave absorbing effects. The reflectivity of fabrics were measured by the means of "arch testing method" in the range from 2~18 GHz with the change of fabric specifications. The results showed that the reflectivities of 12 groups can below-15 dB in the 20 groups testing and the second group which below-20dB was thin and only 440g/m² with the optimized fabric specifications.

Abstract: The finite element model of double etching pits was established, optical performance of multicrystalline silicon wafer before and after etching was simulated by RF MODULE of COMSOL Multiphysics version 3.5a. Optical characteristic of unetching wafer and acidic textured were compared. It is indicates that acidic textured (double etching pits) has low reflectivity, high power flow Y component , the better light trapping. When the wavelength is 600nm, the maximum and minimum value of surface electric field Z component of acidic textured are 1.9 times and 1.4 times respectively than that of unetching wafer, and two extremum value of surface magnetic field Z component are 2.1 times and 1.9 times respectively than that of unetching wafer. Numerical simulation results of Multi hole model are closely with experimental values, which can guide the practical production.

Abstract: Using quantum mechanics plane-wave approach based on the density functional theory, the lattice constants of Ni_xAl at different Ni concentrations (x=1, 3) are predicted. Optical properties such as dielectric function, energy loss function and reflectivity are also investigated. Results show that with the increase of Ni constituent, the location of the peak in loss function moves to the lower energy region, but the peak height increases. At 0eV, the reflectivity increases rapidly with the Ni concentration. The reflectivity of NiAl and Ni₃Al are pronounced in the UV region (not in the visible light region). The dielectric properties, namely the real and imaginary parts of the dielectric function, changed significantly with Ni constituent.