摘要 :
We report and explain the photoluminescence (PL) spectra from crystalline silicon (c-Si) wafers passivated by hydrogenated amorphous silicon (a-Si:H) films under various measurement conditions, utilizing the different absorption c...
展开
We report and explain the photoluminescence (PL) spectra from crystalline silicon (c-Si) wafers passivated by hydrogenated amorphous silicon (a-Si:H) films under various measurement conditions, utilizing the different absorption coefficients and radiative recombination mechanisms in c-Si and a-Si:H. By comparison with the luminescence properties of a-Si:H, we also demonstrate that SiNx films deposited under certain silicon-rich conditions yield luminescence spectra similar to those of a-Si:H, indicating the presence of an a-Si:H-like phase in the SiNx films. This causes a reduction in the blue response of the solar cells via parasitic absorption. In addition, with the ability to detect the specific emission from heavily-doped silicon via band-gap narrowing effects, we can unambiguously separate individual spectral PL signatures of three different layers in a single substrate: the SiNx passivation films, the diffused layers, and the underlying c-Si substrate. Finally, we apply this technique to evaluate parasitic absorption in the passivation films, and the doping density of the diffused layers on different finished solar cells, highlighting the value of this nondestructive contactless, micron-scale technique for photovoltaic applications. (C) 2015 Elsevier B.V. All rights reserved.
收起
摘要 :
A new model for the hot-corrosion of Si-based non-oxide ceramics has been proposed. Older models assume that the high Na_2O-activity required for the corrosive attack of Na_2SO_4 is controlled by the partial pressures of O_2 and S...
展开
A new model for the hot-corrosion of Si-based non-oxide ceramics has been proposed. Older models assume that the high Na_2O-activity required for the corrosive attack of Na_2SO_4 is controlled by the partial pressures of O_2 and SO_3 in the atmosphere. In contrast it could be shown that the extremely low O_2 partial pressure of about 1x10~31 at 900 deg.C at the Si_3N_4/Na_2SO_4-interface is the true cause for the corrosive attack as it enables the decomposition of Na_2SO_4 and the coresponding formation of Na-silicate melts.
收起
摘要 :
A set of model nitride bonded silicon carbide materials has been prepared and examined, with the objective of assessing the relative importance for the development of mechanical strength of the separate variables of silicon nitrid...
展开
A set of model nitride bonded silicon carbide materials has been prepared and examined, with the objective of assessing the relative importance for the development of mechanical strength of the separate variables of silicon nitride content and porosity. The nature of the nitride bonding phase is identified as a strength controlling factor, and this appears to be influenced by silicon powder purity.
收起
摘要 :
Abstract Retinal detachment with subsequent silicone oil retinopexy is not uncommon. A known complication of silicone retinopexy is intraventricular migration of the intraocular silicone oil. While the oil itself does not result i...
展开
Abstract Retinal detachment with subsequent silicone oil retinopexy is not uncommon. A known complication of silicone retinopexy is intraventricular migration of the intraocular silicone oil. While the oil itself does not result in direct pathology, misdiagnosis may lead to an unnecessary diagnostic workup and possibly predispose the patient to surgery intervention. Silicone oil typically appears hyperdense on computer tomography (CT) and hyperintense on T1-weighted magnetic resonance (MR). These imaging findings may mimic a mass or blood products. However, MR imaging of silicone results in chemical shift artifact which should help narrow the imaging differential. We present a patient with incidental CT and MRI findings which resulted in a prolonged hospital course following misidentification of intraventricular silicone oil. Although the imaging differential for an intraventricular lesion may include metastasis, lymphoma, hemorrhage, choroid plexus papilloma/carcinoma, meningioma, subependymoma, and ependymoma, secondary imaging findings should be noted to ensure an accurate diagnosis. In patients with evidence of prior silicone retinopexy, visualization of an intraventricular lesion with associated chemical shift artifact should raise the possibility of intraventricular silicone oil migration.
收起
摘要 :
Recently many kinds of silicones are used for cosmetic applications. We have just developed silicone gels (KSG series), silicone acrylates (KP series), hybrid silicone (powders (KSP series), inorganic power dispersions (SPD series...
展开
Recently many kinds of silicones are used for cosmetic applications. We have just developed silicone gels (KSG series), silicone acrylates (KP series), hybrid silicone (powders (KSP series), inorganic power dispersions (SPD series) and silicone polyglycerols (KF6100 series). We are introducing these innovative new materials for cosmetic applications and explaining the features of them in this paper.
收起
摘要 :
Five major pools of silicon (Si) such as mobile Si, adsorbed Si, Si bound to organic matter, Si occluded in pedogenic oxides/hydroxides and amorphous Si were extracted from three soils namely one each from low, medium and high cat...
展开
Five major pools of silicon (Si) such as mobile Si, adsorbed Si, Si bound to organic matter, Si occluded in pedogenic oxides/hydroxides and amorphous Si were extracted from three soils namely one each from low, medium and high categories of plant available Si using a sequential extraction method. Different pools of Si extracted from soils were in the order of amorphous Si > occluded Si> organic Si > adsorbed Si and mobile Si. The mobile Si and adsorbed Si pools were the smallest pools of Si and ranged from 14.4 to 44.6 mg kg"1 and 4.9 to 89.4 mg kg1, respectively. The content of organic Si and occluded Si ranged from 234 to 619 mg kg"1 and 476 to 1989 mg kg1, respectively. Irrespective of the soils, amorphous Si was found to be the largest pool of Si ranging from 8019 to 16667 mg kg1. Among different pools of Si, organic Si pool showed significant positive correlation with plant available Si while other pools had non-significant. A pot culture experiment was conducted using bulk soil samples with rice as test crop for a period of 60 days, and Si content and its uptake by rice was determined. Typic Rhodustalfs which is medium in plant available Si showed higher Si content (7.0%) and uptake (106 mg pot1) compared to Chromic Haplusterts having high plant available Si. The correlation analysis to know the contribution of different Si pools to Si uptake by rice revealed that occluded, mobile, amorphous and adsorbed pools as the major contributors of Si to rice.
收起
摘要 :
The possibility of creating silicon lasers based on specific few-atomic structural imperfections of a silicon crystal is discussed. These imperfections differ substantially from other defects of the crystal in their high photon em...
展开
The possibility of creating silicon lasers based on specific few-atomic structural imperfections of a silicon crystal is discussed. These imperfections differ substantially from other defects of the crystal in their high photon emissivity, which is a consequence of zero-phonon optical transitions between the localized electron states of the defects considered. A simple model of basic electron processes in the active region of the laser crystal is proposed. Such lasers can operate in the quantum energy range from 0.4 to 1.1 eV at temperatures less than 100 K in a continuous mode. An injection way of excitation and current modulation of the emission intensity up to gigahertz frequencies are possible. The main difficulty in manufacturing such devices is the nonselectivity of today's radiation methods of forming emissive centers in silicon crystals. This difficulty may be obviated by using promising nanotechnology methods of fabrication of the lasers considered.
收起
摘要 :
This work investigates the photo-thermal treatment of solar grade (SG) silicon to reduce impurities to a low level suitable for high efficiency low-cost solar cells application. It describes experiment carried out by using a tungs...
展开
This work investigates the photo-thermal treatment of solar grade (SG) silicon to reduce impurities to a low level suitable for high efficiency low-cost solar cells application. It describes experiment carried out by using a tungsten lamps furnace (rapid thermal processing, RTP) to purify solar grade silicon wafers using a combination of porous silicon (PS) and silicon tetrachloride. This process enables to attract the impurities towards the porous layer where they react with SiCl_4 to form metallic chlorides. The gettering effect was studied using the Hall Effect and the Van Der Pauw methods to measure the resistivity, the majority carrier concentration and mobility. We have obtained a significant improvement of the majority carrier mobility after such thermo-chemical treatment. The gettering efficiency is also evaluated by the relative increase of the minority carrier diffusion length L, measured by the light beam induced current (LBIC) technique.
收起
摘要 :
The symposium "Silicones and Silicone-Modified Materials VI" was hosted by the American Chemical Society (ACS) during the 243 (rd) National Meeting & Exposition in San Diego, California, USA (March 25 -29, 2012). At this "Silicones VI" symposium, I circulated a blank notepad and I then asked the members of the audience for responses to the question "What are the three hot topics in silicon chemistry in March 2012?" These responses are given herein along with a brief discussion of how they may guide us in our future teaching, research and service....
展开
The symposium "Silicones and Silicone-Modified Materials VI" was hosted by the American Chemical Society (ACS) during the 243 (rd) National Meeting & Exposition in San Diego, California, USA (March 25 -29, 2012). At this "Silicones VI" symposium, I circulated a blank notepad and I then asked the members of the audience for responses to the question "What are the three hot topics in silicon chemistry in March 2012?" These responses are given herein along with a brief discussion of how they may guide us in our future teaching, research and service.
收起
摘要 :
Si is an attractive material for anodes in Li ion batteries because of high specific capacity. However, it undergoes significant volume change during electrochemical reactions, causing mechanical fractures and capacity decay, whic...
展开
Si is an attractive material for anodes in Li ion batteries because of high specific capacity. However, it undergoes significant volume change during electrochemical reactions, causing mechanical fractures and capacity decay, which is a serious bottleneck for commercialization. Despite several research attempts to understand the stress evolution in Si, the process remains unclear. A fundamental study of the initial formation of the Li-Si alloy is hence necessary for a better understanding of the stress evolution. In this study, the nucleation and growth of Li-Si alloys on various crystalline Si (c-Si) surfaces during lithiation is observed by the authors. Distinct Li-Si alloys are formed with square pyramid, triangular pyramid, and circular bump shapes on the {100}, {111}, and {110} surfaces, respectively. These unique structures are caused by the preference for Li insertion on the c-Si surface and are maintained even after further growth of the alloy at the outermost layer. The particular structures are assumed to cause a different degree of stress at the reaction front during lithiation. The authors expect that this fundamental study will contribute to an optimal design of the Si anode based on the better understanding of the type of stress present at each c-Si.
收起
原文获取