Diffraction Properties and Application of 3D Polymer Woodpile Photonic Crystal Structure

We present a new technique for modification of diffraction and optical properties of photonic devices by surface application of polymer Three-Dimensional (3D) woodpile Photonic Crystal (PhC) structure. Woodpile structure based on IP-Dip polymer was designed and fabricated by Direct Laser Writing (DLW) lithography method based on nonlinear Two-Photon Absorption (TPA). At first, we investigated diffraction properties of woodpile structure with a period of 2 μm. The structure was placed on a glass substrate, and diffraction patterns were measured using laser sources with different wavelengths. After diffraction properties investigation, the fabricated structures were used in optoelectronic devices by their surface application. Our polymer 3D PhC woodpile structures were used for radiation properties modification of light emitting devices - optical fiber and Light Emitting Diode (LED) and for angular photoresponse modification of InGaAsN-based photodiode. The modification of the far-field radiation patterns of optical fiber and LED and spatial modulation of light coupling into photodiode chip with applied structures were measured by goniophotometer. Quality of fabricated structures was analyzed by a Scanning Electron Microscope (SEM)

Properties of Mechanochemically Synthesized Famatinite Cu3SbS4 Nanocrystals

In this study, we report the optoelectric and thermoelectric properties of famatinite Cu3SbS4 that was mechanochemically synthesized in a planetary mill from powder elements for 120 min in an inert atmosphere. The tetragonal famatinite Cu3SbS4 was nanocrystalline with a crystallite size of 14 nm, as endorsed by Rietveld refinement. High-resolution transmission electron microscopy showed several crystallites in the range of 20–50 nm. Raman spectroscopy proved the purity of the synthesized famatinite Cu3SbS4 and chemical-state characterization performed by X-ray photoelectron spectroscopy confirmed that the prepared sample was pure. The Cu1+, Sb5+, and S2− oxidation states in Cu3SbS4 sample were approved. The morphology characterization showed homogeneity of the prepared sample. The photoresponse of Cu3SbS4 was confirmed from I–V measurements in the dark and under illumination. The photocurrent increase reached 20% compared to the current in the dark at a voltage of 5 V. The achieved results confirm that synthesized famatinite Cu3SbS4 can be applied as a suitable absorbent material in solar cells. The performed thermoelectric measurements revealed a figure of merit ZT of 0.05 at 600 K

Composition related electrical active defect states of InGaAs and GaAsN

This paper discusses results of electrically active defect states - deep energy level analysis in InGaAs and GaAsN undoped semiconductor structures grown for solar cell applications. Main attention is focused on composition and growth condition dependent impurities and the investigation of their possible origins. For this purpose a widely utilized spectroscopy method, Deep Level Transient Fourier Spectroscopy, was utilized. The most significant responses of each sample labelled as InG2, InG3 and NG1, NG2 were discussed in detail and confirmed by simulations and literature data. The presence of a possible dual conduction type and dual state defect complex, dependent on the In/N composition, is reported. Beneficial characteristics of specific indium and nitrogen concentrations capable of eliminating or reducing certain point defects and dislocations are stated

AP-MOVPE Technology and Characterization of InGaAsN p-i-n Subcell for InGaAsN/GaAs Tandem Solar Cell

Tandem (two p-n junctions connected by tunnel junction) and multijunction solar cells (MJSCs) based on AIIIBV semiconductor compounds and alloys are the most effective photovoltaic devices. Record efficiency of the MJSCs exceeds 44% under concentrated sunlight. Individual subcells connected in series by tunnel junctions are crucial components of these devices. In this paper we present atmospheric pressure metal organic vapour phase epitaxy (AP-MOVPE) of InGaAsN based subcell for InGaAsN/GaAs tandem solar cell. The parameters of epitaxial structure (optical and electrical), fabrication process of the test solar cell devices and current-voltage (J-V) characteristics are presented and discussed

Nanostructure and magnetic anomaly of mechanosynthesized Ce1−x_{1-x}Yx_{x}O2−δ_{2-δ} (x ≤ 0.3) solid solutions

Electromagnetic properties of complex oxide solid solutions containing Ce and Y attract increasing interests due to their high application potential. Their properties are known to be dependent on many factors including grain size and crystal defects. Here we focus on unique features of nanocrystalline Ce$_{1-x}$Y$_{x}$O$_{2-δ}$ (x ≤ 0.3) solid solutions prepared via a mechanosynthesis. Mechanically activated CeO$_{2-δ}$ and mechanosynthesized Ce$_{1-x}$Y$_{x}$O$_{2-δ}$ exhibit room-temperature ferromagnetism. The saturation magnetization reaches maximum for the Ce$_{0.9}$Y$_{0.1}$O$_{2-δ}$ solid solution. XPS and Raman spectra show that Ce$^{Zahl}$4+s are partially reduced to Ce$^{3+}$, with simultaneous introduction of oxygen vacancies accumulated on surface of the solid solutions. An analysis of the experimental magnetization data and the determination of both the spin state and the concentration of magnetic carriers revealed that a small part of the Ce$^{3+}$ spins (<1%) is responsible for the magnetic state of the Ce$_{1-x}$Y$_{x}$O$_{2-δ}$ system. Existence of clusters with a short-range antiferromagnetic order is also suspected

Theoretical and Experimental Substractions of Device Temperature Determination Utilizing I-V Characterization Applied on AlGaN/GaN HEMT

A differential analysis of electrical attributes, including the temperature profile and trapping phenomena is introduced using a device analytical spatial electrical model. The resultant current difference caused by the applied voltage variation is divided into isothermal and thermal sections, corresponding to the instantaneous time- or temperature-dependent change. The average temperature relevance is explained in the theoretical section with respect to the thermal profile and major parameters of the device at the operating point. An ambient temperature variation method has been used to determine device average temperature under quasi-static state and pulse operation, was compared with respect to the threshold voltage shift of a high-electron-mobility transistor (HEMT). The experimental sections presents theoretical subtractions of average channel temperature determination including trapping phenomena adapted for the AlGaN/GaN HEMT. The theoretical results found using the analytical model, allow for the consolidation of specific methodologies for further research to determine the device temperature based on spatially distributed and averaged parameters

Optical and Optoelectrical Properties of Ternary Chalcogenide CuInS₂/TiO₂ Nanocomposite Prepared by Mechanochemical Synthesis

In this work, a nanocomposite consisting of ternary chalcogenide CuInS2 and TiO2 was prepared and its optical and optoelectrical properties were investigated. The CuInS2/TiO2 nanocomposite was produced via one-step mechanochemical synthesis and characterized from the crystal structure, microstructural, morphology, surface, optical, and optoelectrical properties viewpoints. X-ray diffraction confirmed the presence of both components, CuInS2 and TiO2, in the nanocomposite and revealed a partial transformation of anatase to rutile. The presence of both components in the samples was also proven by Raman spectroscopy. HRTEM confirmed the nanocrystalline character of the samples as crystallites ranging from around 10 nm and up to a few tens of nanometers were found. The presence of the agglomerated nanoparticles into larger grains was proven by SEM. The measured optical properties of CuInS2, TiO2, and CuInS2/TiO2 nanocomposites demonstrate optical bandgaps of ~1.62 eV for CuInS2 and 3.26 eV for TiO2. The measurement of the optoelectrical properties showed that the presence of TiO2 in the CuInS2/TiO2 nanocomposite increased its conductivity and modified the photosensitivity depending on the ratio of the components. This study has demonstrated the possibility of preparing a CuInS2/TiO2 nanocomposite material with promising applications in optoelectronics in the visible region in an eco-friendly manner

Mechanochemical Synthesis and Characterization of CuInS2/ZnS Nanocrystals

In this study, CuInS2/ZnS nanocrystals were synthesized by a two-step mechanochemical synthesis for the first time. In the first step, tetragonal CuInS2 was prepared from copper, indium and sulphur precursors. The obtained CuInS2 was further co-milled with zinc acetate dihydrate and sodium sulphide nonahydrate as precursors for cubic ZnS. Structural characterization of the CuInS2/ZnS nanocrystals was performed by X-ray diffraction analysis, Raman spectroscopy and transmission electron microscopy. Specific surface area of the product (86 m2/g) was measured by low-temperature nitrogen adsorption method and zeta potential of the particles dispersed in water was calculated from measurements of their electrophoretic mobility. Optical properties of the nanocrystals were determined using photoluminescence emission spectroscopy

Fast, Easy, and Comprehensive Techniques for Microscopic Observations of Fungal and Oomycete Organisms Inside the Roots of Herbaceous and Woody Plants

The roots of herbaceous and woody plants growing in soil are complex structures that are affected by both natural and artificial fungal colonization to various extents. To obtain comprehensive information about the overall distribution of fungi or oomycetes inside a plant root system, rapid, effective, and reliable screening methods are required. To observe both fine roots, i.e., a common site for penetration of fungi and oomycetes, and mature roots, different techniques are required to overcome visual barriers, such as root browning or tissue thickening. In our protocol, we propose using fast, cost-effective, and non-harmful methods to localize fungal or oomycete structures inside plant roots. Root staining with a fluorescent dye provides a quick initial indication of the presence of fungal structures on the root surfaces. The protocol is followed by clearing and staining steps, resulting in a deeper insight into the root tissue positioning, abundance, and characteristic morphological/reproductive features of fungal or oomycete organisms. If required, the stained samples can be prepared by using freeze-drying for further observations, including advanced microscopic techniques