Papers by Keyword: Crystal

Abstract: Zinc oxide (ZnO) crystals form are various applications could be created like in manufacturing ultraviolet laser and photodetectors. Zinc oxide (ZnO) crystals are synthesized by applying electric current on ZnO ceramic bar which are made using powder metallurgy method. By using Scanning Electron Microscope (SEM) and X-Ray Diffractometer (XRD) could be characterized of ZnO sintered bars easily. The different types of crystal are produced such as polygonal, broken stick, flowers, trunks and many more when applied the DC heating until the sample of ZnO will be glows and breaks apart. The loads or pressure and heating method to the sample of ZnO will be affected to the types of crystal growth. The optimum load is 3 metric tonne and will ease the ignition during DC heating due to less porosity of the samples.

Abstract: ZnO has attractive and great properties especially in the fields of photonics, electronics and optics and it is widely used in the manufacturing industry of photodetectors, laser diodes and gas detectors. Therefore, various methods have been carried out to produce ZnO crystals and one of them is the Electric Current Heating method. Electric Current Heating (ECH) method is a fabrication technique applied in researches to grow ZnO crystal on a ceramic bar. This method is preferred because of it is easy to operate in laboratory, low growth temperature and also low cost. In this research, by using powder metallurgy process, Graphene Oxide/GO (in various weight percentage) added into ZnO was pelletized in a compaction die with dimension of 14.95 mm x 30 mm x 40 mm and pressure of 4 bar. The pellet green body was then sintered at 1100 °C with rate 10.0 °C/min for 3 hours. The sintered GO added ZnO ceramic was cut into ceramic bar with dimensio of 13mm x 2mm x 2mm. ECH with current 3 A and applied voltage of 30 V was used to heat the ceramic bar to produce crystals. Under scanning electron observation, it was found different crystal-like structures for each percentage GO addition. UV-Vis measurement has shown that each crystal-like structure of a GO added ZnO has own degree of energy absorbsion because of different band gap. Addition GO into ZnO would increase band gap of pure ZnO.

Abstract: A model of the rearrangement of the domain structure of the Tb_0.2Y_2.8Fe₅O₁₂ garnet ferrite in the temperature region of the spontaneous reorientation of the easy magnetization axis is proposed, which makes it possible to consistently describe (at a qualitative level) the entire set of experimental results obtained. The latter makes it possible to make a choice in favor of the fluctuation mechanism of nucleation of domains of a new magnetic phase in the process of reorientation of the direction of the easy magnetization axis.

Abstract: Due to the booming development of the automation industry and the transportation industry, the mechanical components are prone to wear under long-term operating conditions. To improve the wear resistance, effects of the rolling directions on wear of the aluminum alloys are studied. An optical microscope is used to analyze the crystal phase, and the correlation between the crystal grains and the rolling direction is studied. This study can therefore establish a key technology for improving the wear resistance of aluminum alloys.

Abstract: Boron, aluminum, and nitrogen are major and critical elements in silicon carbide. The concentrations of these elements influence the electrical properties of silicon carbide and also the generation of defects. Purification was executed in the powder manufacturing process. High purity powder was used to grow the crystal, which was then sliced into wafers in this work. Secondary ion mass spectroscopy (SIMS) and glow discharge mass spectrometry (GDMS) were used to measure boron, aluminum, and nitrogen concentrations in wafer and powder to compare the concentration difference. The concentration of the elements varies depending on the element’s physical property. Transfer coefficient is defined as the ratio of element concentration in wafer to powder, which is interesting to realize the element behavior in PVT process and studied in this work.

Abstract: We report on the results of intense third party evaluation of the COLD SPLIT technology. In total nine different SiC manufactures supplied test material. The results confirm the tremendous potential of the technology with total kerf losses per wafer of less than 100μm. Furthermore, our general approach led to comparable results for all vendors. The vendor specific difference like lateral doping level were addressed via control loops in our lasering process. These loops take crystal properties into account and adjust the applied laser energy and the depth of the laser process accordingly. Even the current best case results of sub 80μm split loss per wafer are dominated by systematic effects, which are addressed by continuous improvement efforts.

Abstract: Scattering of elastic waves in calcium molybdate films is considered. The transformation of elastic waves as a result of six-beam diffraction in an anisotropic layer is analyzed. This analysis is based on the transfer matrix method. The distribution of incident wave energy between six scattered waves is characterized by conversion coefficients. The method for conversion coefficients calculations is presented. It does not require solving algebraic problem on eigenvalues for waves in an anisotropic layer. Features of dependencies of conversion coefficients of CaMoO₄ layers on angles of incidence, frequency and the thickness of the layer are demonstrated.

Abstract: The search for inexpensive and efficient methods of forming thin BaSi₂ films as a promising material for photovoltaic is an actual task. The co-deposition of Ba and Si atoms with alloy thickness of 100-120 nm on the silicon substrate at room temperature with following annealing (SPE method) was proposed. Ba-Si alloy compounds then were thermally annealed at different temperatures and three samples were formed: #1 at T = 600 ° C, #2 at T = 700 ° C and #3 at T = 800 ° C. Polycrystalline films with an orthorhombic BaSi₂ structure were formed by XRD, UV-VIS, FIR and Raman spectroscopies data. BaSi₂ grains in samples #1 and #2 have sizes 62-64 nm and 86 nm in the sample #3 from XRD data calculations by Scherrer formula. Proposed growth method resulted to strong compression of the BaSi₂ unit cell volume on 1.78 – 2.70%. The strongest compression was observed after annealing at 800 °C, which was accompanied by desorption of a noticeable amount of barium and a strong decrease in the film thickness in the sample #3. The formation of nanosize Si clusters was confirmed by Raman data for samples #2 and #3, but they did not observed in the sample #3. So, the film, formed at 800 °C, is the most qualitative in terms of structure and single-phase BaSi₂, but with strong decrease of initial Ba-Si alloy thickness due to Ba desorption.

Abstract: The article describes application of using liquid crystals in area of contactless scanning. Concrete application is showed in a turning process oriented to controlling and direction. Polarising attributes of liquid crystals is used in integration of exactness and sesitivity of electrostatical scanning principe and stability and simplicity of optical scanning, whole system has a higher resistance to an exterior disturbing actions and resistance to a possible electrostatical discharge. The article describes a consecution and conditions of practical measuring of principe ́s attestation, elaboration and interpretation of measuring answer.

Abstract: One dimensional (1-D) organic materials have a bright prospect in the field of optoelectronics. Intrigued by these, 1-D uniform sub-micrometer tris-(8-hydroxyquinoline) gallium (GaQ₃) rods were prepared with surfactant by an extremely facial method. The GaQ₃ rods with hexagonal cross sections had excellent crystallinity and optical properties. The measurement of the absorption spectrum showed that there was an obvious blue shift comparing with the GaQ₃ film. This can be explained by that the molecular packing in the α-phase rods has a looser interligand spacing compared with the GaQ₃ film, consequently resulting in reduced orbital overlap and larger energy gap.