Band gap

Xem 1-15 trên 15 kết quả Band gap
  • Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: First-Principles Study of the Band Gap Structure of OxygenPassivated Silicon Nanonets

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  • In this paper, materials of ZnS:Cu, ZnS:Mn and ZnO:Co were prepared by ceramic method and co-precipitated method. The presence of transition metals such as Cu2+(3d9), Mn2+(3d5) in ZnS and Co2+(3d7) in ZnO make blue bands at around 476 nm, 486 nm and green band at around 514 nm disappeared. Simultaneously, there are luminescence bands at around 533 nm, 582 nm, 693 nm for bulk samples of ZnS:Cu, ZnS:Mn, ZnO:Co and 603 nm for nanocrystalline sample of ZnS:Mn.

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  • Introduction to LEDs: How LEDs work + some points. Comparison with other sources of light. LED in communication. Blue &White LED technologies. How they are made? Their application? Brief about blue laser? Stands for light emitting diode. Semiconductor device: p-n junction forward-biased.current emits incoherent narrow spectrum light (due to recombination in transition region near the junction.) Color of the emitted light depends on the chemical of the semiconducting material used. (Near-ultraviolet, visible or infrared.)...

    ppt52p lehieukutek 26-12-2009 180 132   Download

  • First off, it’s all about the lumens. Lumens are the visible light given off by a source, and they are the ultimate goal. Wattage has often been confused with lumens, thanks to how incandescent bulbs are rated (everyone knows that a 60W bulb is not as bright as a 100W one), but more efficient lighting technologies have greatly changed the relationship between wattage (essentially power usage) and lumens (light output). For example, an incandescent might operate at about 12-15 lumens-per-watt (lm/W), while an LED bulb will be in the range of 40-50, a much greater luminous efficacy...

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  • Silicon carbide (SiC) is an interesting material that has found application in a variety of industries. The two best known applications of this material are its use as an abrasive material and its more recent use as a wide band gap semiconductor for high power, high temperature electronic devices. The high hardness of this material, known for many years, led to its use in machining tools and in other structural applications.

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  • Hydrogenated amorphous silicon, a new form of a common element, is a semiconductor that has come of age. Its scientific attractions include a continuously adjustable band gap, a usable camer lifetime and diffusion length, efficient optical transitions, and the capability of employing either nor p-type dopants. Furthermore, it can be fabricated very easily as a thin film by a technology that not only inherently escapes the expenst: of crystal perfection but also requires significantly smaller amounts of raw materials....

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  • Aeberhard Nanoscale Research Letters 2011, 6:242 NANO EXPRESS Open Access Theory and simulation of photogeneration and transport in Si-SiOx superlattice absorbers Urs Aeberhard Abstract Si-SiOx superlattices are among the candidates that have been proposed as high band gap absorber material in allSi tandem solar cell devices. Owing to the large potential barriers for photoexited charge carriers, transport in these devices is restricted to quantum-confined superlattice states.

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  • Chemical doping nitrogen in to TiO2 crystal network by methods of sol-gel and impregnation was presented. The obtained nitrogen-doped TiO2 materials were characterized by different techniques such as XRD, SEM, UV-VIS. It was shown that samples have very uniform nano size, anatas structure and low level of band-gap energy (Ebg ~ 2.2 eV, ~ 500 - 600 nm). Their activity and kinetic were also studied and the results proved that in comparison with P25, the obtained nitrogen-doped TiO2 had higher activity and photo-quantum efficiency in organic disintegrated reaction under solar radiation.

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  • Mục tiêu: Xác định tỉ lệ gen SMN1/SMN2 ở người lành mang gen bệnh Werdnig-Hoffmann. Phương pháp: Chúng tôi dùng phản ứng khuếch đại cạnh tranh tạo ra các sản phẩm PCR của SMN1 và SMN2. Sau đó, làm đứt đoạn sản phẩm PCR của gen SMN bằng men Hinfl. Sản phẩm thu được sẽ được chạy điện di trên gel, rồi scan bằng máy ảnh Polaroid dưới tia cực tím, và phân tích đậm độ (phần mềm 1.16/ppc NIH Image) đối với hai dãi band 101 bp (SMN2) và 78 bp (SMN1).

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  • QDs play an important role mainly in the imaging and as highly fluorescent probes for biological sensing that have better sensitivity, longer stability, good biocompatibility, and minimum invasiveness. The fluorescent properties of QDs arise from the fact, that their excitation states/band gaps are spatially confined, which results in physical and optical properties intermediate between compounds and single molecules. Depending on chemical composition and the size of the core which determines the quantum confinement, the emission peak can vary from UV to NIR wavelengths (400–1350 nm).

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  • Purified, nonubiquitinated growth-associated protein of 43 kDa (GAP-43) was attacked by purified reticulocyte 20S proteasomebutnotby the26Sproteasome.Cleavageyielded 12 N-terminally labelled GAP-43 fragments that could be resolved by SDS/PAGE. Inhibitor experiments suggested that proteasomeb1 activity yielded the resolved bands and that proteasome b5 activity generated nonresolvable frag-ments. Processive degradation, yielding only nonresolvable fragments, therefore did not occur.

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  • DSB-FC (AM): công suất sóng mang chiếm 2/3 tổng công suất DSB-FC (AM): sóng mang không mang thông tin DSB: sử dụng gấp đôi tần số so với SSB Chì có băng cạnh chứa thông tin thông tin USB = thông tin LSB truyền tải cả 2 băng cạnh là dư thừa DSB-FC: không lợi về băng thông và công suất DSB-SC: không lợi về băng thông

    ppt52p feteler 27-11-2012 16 1   Download

  • To maximize the extent of the photonic bandgap in a finite-height photonic-crystal (PhC) slab one can increase the fill-factor in the PhC lattice. Among the realistic choices of possible 2D lattices, high fill- factor triangular lattices of cylindrical holes in a high index dielectric, namely silicon, are by far the most commonly used. In this paper, we present a method for fabrication of very high fill-factor PhC devices in silicon-on-insulator (SOI) substrates using electron-beam lithography and high-aspect-ratio reactive-ion etching (RIE).

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  • Sometimes history seems to repeat. Even in the so-called ‘mature’ technological fields. When the radio pioneers such as Heinrich Hertz, Guglielmo Marconi, and Alexander Stepanovich Popov made their first experiments of wireless transmission more than a hundred years ago using spark-gap transmitters with simple coherer-detectors they did not care which ‘frequency band’ they were using, nor did they worry about their signals being ‘spectrally efficient’ or ‘band limited’. The world of radio frequency regulation was very simple then since regulations have not yet existed.

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  • The acoustomagnetoelectric (AME) effect in a superlattice (SL) is investigated for an acoustic wave whose wavelength $\lambda =2\pi/q$ is smaller than the mean free path $l$ of the electrons and hypersound in the region $ql\gg1$ (where $q$ is the acoustic wave number) . The analytical expression for the AME current $j^{AME}$ is calculated in the case of relaxation time of momentum $\tau$ is constant approximation. The result indicates that the existense of $j^{AME}$ in a SL may be due to the finite gap band , and the periodicity of the electron spectrum along the SL axis.

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