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Hall Effect in Germanium Doped with Different Impurities
摘要： The influence of different impurities on the kinetics of electronic processes in n-Ge?Sb? single crystals is investigated. A substantial decrease in the charge carrier mobility in the region of predominantly impurity scattering (at 77 K) in n-Ge?Sb + Si? crystals, as well as in germanium crystals doped with the rare-earth elements, is detected, and this effect is explained.
关键词： Hall effect,charge carrier mobility,germanium,Hall coefficient,impurities
更新于2025-09-19 17:15:36
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Theoretical study of the structural and electronic properties of impurities in non-passivated silicon thin nanowires
摘要： In this work, we report theoretical results for the presence of the B, C, N, O and F as impurities in non-passivated [001] thin silicon nanowires. The results for the formation energies show that some dopants tend to segregate to the nanowire surfaces, as observed for passivated [110] ones, but at the double negative charge state. The most stable site for the considered impurities is the interstitial one, where the dopants make bridges with the lateral surface Si atoms, below to this surface, except for the oxygen and ?uorine ones, which stay close to the central Si atom. For the neutral carbon, nitrogen and ?uorine impurities, the surface π-states located at the facets are ?lled and a small bandgap appears in the calculated impurity band structures. However, if they were at the double negative charge state, the nanowire metallicity is recovered. Considering the boron and oxygen dopants, the neutral charge state enhances the metallic character at the opposite side of the nanowire where they are, which is reduced when two extra electrons are injected in the system and thus, opening slightly the nanowire bandgap. Our results clearly indicate that doping (or creating vacancies in) these nanowires with acceptors, as well as with hydrogen atoms, can reduce the thin nanowire metallic behavior.
关键词： Electronic structure,Silicon thin nanowires,First row impurities,DFT calculations,Formation energies
更新于2025-09-19 17:15:36
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GaN grown by metalorganic vapor phase epitaxy
摘要： We report on residual impurities in semi-polar (3031) and (2021) GaN homo-epitaxial layer grown by metal-organic chemical vapor deposition. The (3031) and (2021) GaN layer showed atomically smooth surface and clear steps toward [0001] and [000-1], respectively. The residual impurity concentrations of oxygen and carbon were below the detection limit of secondary-ion mass spectroscopy. Low-temperature photoluminescence revealed that (2021) GaN layer consisted free excitons and Si donor bound excitons, along with two-electron satellite lines and longitudinal optical (LO) phonon coupling transitions. The results indicate semi-polar (3031) and (2021) GaN epitaxial layers are promising candidates in obtaining a high quality GaN drift layer for vertical GaN devices.
关键词： B2. Semiconducting III-V materials,A3. Metalorganic chemical vapor deposition,B1. Nitrides,A1. Crystal structure,A1. Impurities
更新于2025-09-19 17:15:36
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Laser-induced damage of black glass before and after surface treatment by containing impurities-SiO2 film during ultra clean manufacturing
摘要： Ultra-clean manufacturing is an indispensable key technology for inertial confinement fusion (ICF) to generate clean and sustainable energy, but the pollutants from laser-induced damage are a threat to ultra-clean manufacturing. Here we investigate the damage of black glass in a high laser fluence system, which refers to high fluence laser beams in fusion class laser systems. Results show a significant dependence of damage parameters on the laser pulse duration at 355 nm before and after surface treatment by SiO2 films, which include the laser-induced damage threshold (LIDT), morphology and depth. The simulation indicates that the LIDT of SiO2 films on black glass is improved obviously, which is 14.1 J/cm2, while that of normal black glass is 10.2 J/cm2. The presence of impurities will aggravate the damage of the thin films and pollutes the laser system. LIDT of SiO2 films containing impurities is only 3.6 J/cm2. The experiments show that the average LIDT of black glass is 9.54 J/cm2 while that of thin films with impurities is no more than 4.12 J/cm2. These salient results provide a new concept for the protection of absorbing stray light for ultra-clean manufacturing.
关键词： Black glass,Sustainable energy,Impurities,Ultra-clean manufacturing,LIDT
更新于2025-09-19 17:13:59
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Killer impurities in vacuum chamber that affect the lifetime of organic light-emitting diodes
摘要： We have evaluated a method to investigate killer impurities in vacuum chambers that affect the lifetimes of organic light-emitting diodes (OLEDs) processed in these chambers. In addition to chambers for the deposition of organic and metal films, an exposure chamber was installed to expose the OLEDs to impurities and residual water in a vacuum chamber during device fabrication. We studied a method to investigate the effects of these vacuum chamber impurities after establishing the reproducibility of the device lifetimes. These device lifetimes were affected by the cleanliness of the exposure chamber. Increased exposure times led to shorter device lifetimes, even if the contact angle in the exposure chamber was reduced to less than 5° using plasma cleaning. Furthermore, the device lifetime did not degrade when the partial pressure of water within the exposure chamber was reduced using a cryotrap. We were also able to evaluate the Kapton tape and vacuum greases that were used and determined whether they affected the device lifetime. These results suggest that the influence of residual water and impurities can be separated and it would then be possible to evaluate the influence of the impurities alone on the device lifetime.
关键词： device lifetime,plasma cleaning,cryotrap,OLED,impurities,vacuum chamber
更新于2025-09-19 17:13:59
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Laser and Optical Sounding of the Atmosphere
摘要： Lidar and searchlight instruments and techniques for atmospheric research developed at the V.E. Zuev Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences, in recent years are described. Key results obtained using these techniques are presented.
关键词： aerosol,atmosphere,gas impurities,lidar,scattering
更新于2025-09-19 17:13:59
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Molecular engineering of an electron-transport triarylphosphine oxide-triazine conjugate toward high-performance phosphorescent organic light-emitting diodes with remarkable stability
摘要： Organic electron-transport materials are an essential component to boost performances and stability of organic light-emitting diodes. We present a robust organic electron-transport compound 3-(6-(3-(4,6-bis(4-biphenylyl)-1,3,5-triazin-2-yl)phenyl)pyridin-2-yl)phenyldiphenylphosphine oxide by facilely coupling the triphenylphosphine oxide moiety to the 2-phenyl-4,6-bis(4-biphenylyl)-1,3,5-triazine unit via a 2,6-pyridinylene linker. It is well soluble in weakly polar solvents and possesses a high Tg of 123 °C with an exceptional Td≈470 °C at 1% weight loss and deep HOMO/LUMO levels of ca. ?6.45/?3.06 eV. The phosphorescent spectrum measured in solid state at 77 K reveals a notable triplet energy of 2.88 eV. n-Doping with 8-hydroxyquinolatolithium (Liq) produces the electron mobility value of 4.66×10?5–3.21×10?4 cm2 V?1 s?1@(2–5)×105 V cm?1. Moreover, the contrasting solubility of the bromo reaction intermediate and the new compound in alcoholic solvents facilitates separation. The characterizations of bottom- and top-emission green phosphorescent OLEDs involving this single Liq-doped electron-transport layer reveal long stability. In particular, the latter provides outstanding performances with 77.4 cd A–1 (corresponding to an EQE of 18.7%) and 86.8 lm W–1@ca. 1000 cd m?2, based on the green emitter bis(2-phenylpyridine)(2-(4-methyl-3-phenylphenyl)pyridine)iridium(III). Moreover, driven by a constant current for ca. 640 h, the initial luminance of 1000 cd m–2 appears almost no decay.
关键词： halogen impurities,heterocycles,electron-transport materials,lifetime,phosphine oxides
更新于2025-09-19 17:13:59
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Intense red emission on dilute Mn-doped CaYAlO4-based ceramics obtained by laser floating zone
摘要： The laser floating zone (LFZ) technique was used to produce polycrystalline fibers composed by P21/c monoclinic Y4Al2O9 (YAM) and P?421m tetragonal CaYAl3O7 (CYAM) phases embedded into I4/mmm tetragonal CaYAlO4 matrix. The scanning electron microscopy and X-ray diffraction patterns put in evidence the strong effect of growth rate on the microstructural and phases’ evolution. Besides the microstructural and structural analysis, complementary optical techniques as photoluminescence (PL), PL excitation (PLE), and lifetime measurements were used to characterize the produced fibers. The nonintentionally doped fibers were shown to exhibit an intense deep red emission likely due to Mn4+ trace impurities. From the PLE measurements, average crystal field strength was estimated with Dq/B ~ 2.94. Temperature-dependent PL measurements revealed that the red luminescence is due to the overlap of transitions from the almost electronic degenerate 2E and 4T2 excited states to the 4A2 ground state. The emission from the two excited states arises due to the breakdown of the adiabatic approximation. The overall luminescence intensity of the red emission was found to decrease from 11 K to RT, and the internal quantum efficiency, estimated from the ratio of the integrated luminescence at high and low temperatures, was found to be 60%. Time-resolved spectroscopy indicates a single decay time of ca. 2.0 ms at room temperature, corresponding to the spin and parity forbidden 2E → 4A2 transition.
关键词： Laser floating zone,Crystal field strength,Polycrystalline fibers,Mn4+ trace impurities,Red emission
更新于2025-09-16 10:30:52
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Surface Refining by Laser Scanning on Silicon Wafers
摘要： A YAG continue-wave laser has been used to refine the surface of silicon wafers in this study. During laser scanning, the irradiated region of the surface of the wafer experienced melting and subsequent recrystallization, which results in a redistribution of metal impurities in the molten pool along the depth direction. Cross-sectional micrographs of irradiated wafers have a clear boundary, which confirms the process of recrystallization, and the depth of molten region depends on the scanning parameters and the size of wafer. Secondary ion mass spectrometry measurements have been carried out to characterize the concentration of metal impurities. After redistribution of metal impurities, a final relative purity region was formed close to the surface. SIMS measurements demonstrate that the metal impurity concentration of the purity region has significantly reduced. The mechanism of the redistribution process of metal impurities in the molten pool has been qualitatively analyzed. All of the experimental results support that the CW laser scanning technology can effectively refine the specific surfaces of silicon wafers, and this technology has a great potential in the field of solar cells.
关键词： Silicon wafer,Laser scanning,Refining,Metal impurities,Recrystallization
更新于2025-09-16 10:30:52
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Numerical modeling of carbon distribution and precipitation during directional solidification of photovoltaic silicon
摘要： Numerical modeling is used to investigate carbon distribution and precipitation in directional solidification of multicrystalline silicon. Computations are performed for samples of 6 cm in diameter grown in a Vertical Bridgman Freezing (VGF) system starting from silicon feedstock with different grades of contamination in carbon. The value of the unknown reaction rate coefficient governing the carbon precipitation in the silicon melt was estimated in the present work by comparing the numerically computed concentration profiles to the experimental results taken from the literature. Numerical results show that the growth rate has a significant influence on the interface deflection, melt convection and carbon precipitation. It is found that the silicon samples grown from the melts of low carbon contamination (< 1018 at/cm3) exhibit low content in SiC precipitates, even if they are solidified at high growth rates (1–2 cm/h). The samples with high initial carbon contamination (5 × 1018 at/cm3) should be solidified at much lower rates (0.2 cm/h) in order to avoid the formation of SiC precipitates.
关键词： Carbon transport and precipitation,Directional solidification,Impurities,Semiconducting silicon,Computer simulation
更新于2025-09-16 10:30:52