Papers by Keyword: UV

Abstract: 4H silicon carbide (SiC) based pin photodiodes with a sensitivity in the vacuum ultraviolet spectrum (VUV) demand newly developed emitter doping profiles. This work features the first ever reported 4H-SiC pin photodiodes with an implanted p-emitter and a noticeable sensitivity at a wavelength of 200 nm. As a first step, Aluminum doping profiles produced by low energy ion implantation in 4H-SiC were characterized by secondary-ion mass spectrometry (SIMS). Photodiodes using these shallow emitters are compared to one with a deep p-emitter doping profile employing IV characteristics and the spectral response. SIMS results demonstrate the possibility of shallow Alimplantation profiles using low implantation energies with all emitter profiles featuring characteristic I-V results. For some shallow doping profiles, a meassurable signal at the upper limit of the VUV spectrum could be demonstrated, paving the way towards 4H-SiC pin photodiodes with sensitivities for wavelengths below 200 nm.

Abstract: Cobalt oxide thin film (Co₃O₄) has been prepared from cobalt chloride with distilled water on conducting glass substrates Fluorine doped Tin Oxide (FTO) at (400^ºC) by depositing chemical spray pyrolysis, with thickness (200 nm). The structural properties are studied by XRD. Also, optical properties and electrical properties of Co₃O₄ thin film are studied by UV spectroscopy and Cyclic voltammetry (CV) respectively. The effects of gamma irradiation on optical properties are also examined. XRD results showed that the film was polycrystalline with cubic structure having preferred orientation (111). The as-prepared Co₃O₄ film exhibits a noticeable EC behaviour with reversible colour which changes from dark grey to pale yellow with bleaching time (55 s) and colouring time (40 s). After irradiation, the optical properties showed that as the transmittance decrease leads to decrease the direct optical band gap from (3.68eV) to (3.55eV)

Abstract: In order to explore more functional supported probe material, the ultraviolet absorbance together with fluorescence properties of a probe with the structure of salicylaldehyde Schiff-base in various solvents and pHs were investigated after its synthesis. When the concentration of Cr³⁺ ion was in the range of 3~7×10^-5 mol•L^-1, the complex reaction between the probe and Cr³⁺ could be used for quantitation of the latter, which was developed by UV absorbance intensity of the complex and the concentration of Cr³⁺ ion. Ultraviolet analytic results determined that they were complexed in the molar ratio of 1:1. Finally, the MOF-supported probe material was successfully synthesized for further application, which realized the immobilization of the probe through simple operations.

Abstract: The silicon-aluminum oxide-nitride-silicon oxide-silicon (hereafter SANOS) could be candidates for ultra violet total dose (hereafter UV TD) nonvolatile sensors. In the case of SANOS UV TD radiation sensors, the UV radiation induces a significant increase of threshold voltage V_T. The changes of V_T for SANOS after UV radiation have a correlation to the UV TD as well. In this paper, the performance for capacitor types of SANOS UV TD nonvolatile sensor were discussed in detailed. The SANOS capacitor device in this study has demonstrated the better feasibility for UV TD nonvolatile sensor application.

Abstract: 4H-SiC UV-photodetectors based on full-epitaxial p ⁺p^-n⁺ multilayer structures werefabricated. The diodes were irradiated with fast neutrons up to the fluence of 1·10¹⁴ cm^-2 . Current-voltage characteristics, life time of non-equilibrium charge carriers as well as photosensitivityspectra of the diodes before and after irradiation were investigated. The studies showed that PiNUV-photodiodes with base doping below 1·10¹⁵ cm^-3 retain their performance up to the fluence of5·10¹² neutrons per cm² . The further increase in fast neutron fluence stimulates the creation ofexcessive deep recombination centers. This leads to degradation of I-V-characteristics, reduction ofcarrier life time and, consequently, to degradation of the photosensitivity of devices.

Abstract: In this paper, waterborne ultraviolet (UV)-curing wood coatings were modified by nano MgCO₃ puree, and prepared by optimizing the process parameters. The mechanical properties (hardness, adhesion and resistance impact strength) and gloss of waterborne UV-curing wood coatings modified by nano MgCO₃ puree were tested. It was found that the mechanical properties of coatings increased when nano MgCO₃ content increased from 0 to 3.0%. Waterborne UV-curing wood coatings had good hardness, adhesion and impact strength when the nano MgCO₃ content was 3%-4%. The hardness was 3H, the adhesion was grade 1, and impact strength was 40 kg∙cm. However, when nano MgCO₃ content was higher than 4%, the mechanical properties of coatings decreased. As the nano MgCO₃ content gradually increasing, the gloss of waterborne UV-curing wood coatings modified by nano MgCO₃ puree decreased. When the nano MgCO₃ content was 4.0%, the gloss of coating was 33%. When the nano MgCO₃ content exceeded 4.0%, the gloss of waterborne UV-curing wood coatings displayed matte.

Abstract: Special-effect finishes are used in many applications to create new color impressions, pronouncing the design of a product and at the same time making the product appear alive. Total appearance conducting color and geometrical factors such as gloss, shape, etc. Gloss is an attribute of visual appearance that originates from the geometrical distribution of the light reflected by the surface. This paper presents new technologies that were developed to objectively describe total impression of appearance special effect finishes, coated composites and automotive paints after real live tests.

Abstract: Nowadays, the discharge of synthetic dyes effluents into water system has created serious water contamination problems which could gravely impact the quality of human life. Photocatalytic oxidation (PCO) by TiO₂ has shown superior performance on towards the remediation of various organic pollutants. In this study, two dimensional (2D) graphene oxide (GO) sheets supported titanium dioxide (TiO₂) nanoparticles were successfully synthesized by a simple and efficient sol-gel method using titanium isopropoxide (TTIP) and GO as the precursor. The graphite powder was first oxidized into hydrophilic GO using modified Hummer’s method followed by the addition of titanium solution. The resulting nanocomposites were then applied in the PCO of methyl orange under UV irradiation. The TiO₂ nanoparticles were spherical in shape, with a particle size of 20-30 nm were well-deposited on the GO sheets. The presence of anatase phase in GO/TiO₂ was confirmed by the XRD studies. The nanocomposites exhibited enhanced photocatalytic activity than TiO₂, probably due to the addition of graphene oxide which retard the electron-hole recombination in the hybrid material.

Abstract: We have demonstrated the possibility for epitaxial regrowth of crystalline SiC by laser melt annealing. The quality of the recrystallization is analyzed by XTEM, EELS, electron diffraction and XRD. The annealing guarantees a uniform activation achieved both in melting and solid phase. Carbon graphitization on the top surface and a crystallized silicon layer below is observed as an effect of the high temperature and the melting phase.

Abstract: This paper describes the fabrication, characterization, and simulation of 4H-SiC pin-photodiodes for solar UV radiation detection. The devices were produced with an aluminum implanted emitter unlike most previously published detectors which use epitaxy for all applied doping regions (see e.g. [1-3]). They were electrically characterized at different temperatures with and without UV-illumination and afterwards a spectral analysis of the photocurrent was performed. A quantum efficiency up to 55% at 260 nm will be shown. Furthermore, the capability of the diodes for visible blind sun UV monitoring e.g. within a building, is demonstrated.