Large Si Research Articles

Fabrication of Large Surface Area Semitransparent Monocrystalline Si Solar Cells

An experimental technique is presented for fabricating large surface area semitransparent monocrystalline Si solar cells. The semitransparency is achieved by laser-cutting two-dimensional periodic lattices of ellipses through industrially manufactured Si cells. A novel two-level metal base was invented for minimizing cell breakages during laser cutting. The periodic lattices consist of a large number of ellipses, so as to achieve uniform distribution of the transmitted solar radiation. High efficiencies over 13% are deduced from the I–V curves, recorded under physical sunlight, for all fabricated cells with a 5% transparency.

In-situ Observation of Tensile Fracture in A357 Casting Alloys

The mechanism of damage evolution and fracture in A357 casting alloys was investigated by in-situ scanning electron microscopy (SEM) tensile testing. Different microstructures of A357 casting alloys were produced by eutectic Si modification and T6 heat treatment. It is shown that microcracks in these alloys are predominantly formed in eutectic Si particles. Large and elongated eutectic Si particles in unmodified alloy show the greater tendency to cracking, whereas cracking of small and round eutectic Si particles in Sr modified and T6 heat treated alloys is relatively lag. The crack mainly propagates along the broken eutectic Si particles in unmodified and Sr modified alloys or along the deepened shear bands in T6 heat treated alloy with accumulating the applied strain. The results were discussed in terms of Weibull statistics and the fracture models were established.

Crystallisation characteristics of primary silicon particles in cast hypereutectic Al–Si alloy

The crystallisation characteristics of primary silicon particles in a cast hypereutectic Al–Si alloy were examined using various casting processes. The size of the primary silicon particles depends on the cooling rate. However, the primary silicon particles cannot be crystallised completely when the cooling rate is >20 K s−1, since uncrystallised Si atoms migrate to the regions at low cooling rates, producing large primary Si particles. Moreover, turbulent metal flow under conditions of high cooling rate leads to the macrosegregation of the primary Si particles, resulting in poor mechanical properties. From the crystallisation characteristics obtained, a suitable solidification criterion can be proposed.

Thermal stress induced void formation during 450 mm defect free silicon crystal growth and implications for wafer inspection

When pulling large diameter Si crystals from a melt close to the Voronkov criterion, small changes in pulling speed and thermal gradient can lead to the formation of voids leading to detrimental pits on the polished wafer surface. The creation of voids is mainly due to the lowering of the vacancy formation energy due to increased thermal compressive stress. The small size and low density of the formed voids when pulling crystals close to the Voronkov criterion conditions are a challenge for wafer surface inspection tools and possible solutions are discussed.

The modulation on luminescence of Er3+-doped silicon-rich oxide films by the structure evolution of silicon nanoclusters

A series of silicon-rich oxide (SRO) and erbium-doped SRO (SROEr) films imbedded with structural tunable silicon nanoclusters (Si NCs) have been fabricated using sputtering followed by post-annealing. The coalescence of Si NCs is found in the films with large Si excess. The energy transfer rate between Si NCs and Er3+ is enhanced, but the luminescence efficiencies of both Si NCs and Er3+ are reduced by the coalescent microstructures. Optimization of the microstructures of Si NCs is performed, and the preferential optical performance for both Si NCs and Er3+ could be achieved when Si NCs were separated in microstructures.

Microstructure and phase analyses of melt-spun Si-Ni base anode materials for Li-ion battery

Si-based anode composite materials have been studied to improve the performance and the durability of Li-ion secondary batteries in this study. Si-Ni-Al, Si-Ni-Cu and Si-Ni-Cu-Al base alloys were designed and rapidly solidified at the cooling rate of about 106 °C/sec by optimizing the melt spinning. The ribbons were characterized using FE-SEM equipped with EDS, X-ray diffractometer and HR-TEM. The thin ribbons of Si-Ni-Al alloy consisted of nano-sized Si particles and amorphous matrix, which was regarded as an ideal microstructure for the anode material. At the wheel side of the ribbon, 20–30 nm of Si particles were formed (Zone A); whereas at the air side relatively large Si particles were distributed (Zone B). The Si-Ni-Cu alloy showed coarser Si particles than the Si-Ni-Al alloy, and its matrix consisted of NiSi2, Cu3Si and amorphous structures. Finally, the microstructure of the Si-Ni-Cu-Al alloy strips was composed of coarse Si particles, CuNi, Al4Cu9, NiSi2, and unknown phases, and the size of those Si particles were too large to be used for the anode materials.

Evolution of negative SI‐induced ionospheric flows observed by SuperDARN King Salmon HF radar

The spatial evolution of vortex‐like flow structures induced by a negative sudden impulse (SI−) is studied on the basis of SuperDARN King Salmon HF radar (KSR) with other ground and satellite data. A large dip in the solar wind density induced a fairly large SI− with a SYM‐H amplitude of ∼40 nT. The SI‐induced ionospheric flow signatures in the evening sector (MLT ∼ 19 h) were observed by KSR as a westward flow associated with the preliminary impulse (PI) followed by a more intense eastward flow with the main impulse (MI) in the sub‐auroral region of the magnetic latitude ∼60–70 deg, consistent with the local ground magnetic field observations. Following the first PI‐MI flow sequence, KSR saw a second and possibly third sequence of flow variation which were much smaller in flow amplitude than the first pair but showed qualitatively very similar flow variations and latitudinal/longitudinal propagation characteristics. These observations can be interpreted as aftershocks of the first PI‐MI; the same sequence of vortices and field‐aligned currents were generated and then drifted anti‐sunward with the same mechanism, namely the pumping motion of the dayside magnetosphere. These results are qualitatively consistent with predictions suggested by recent numerical simulations.

The Vegetation Silica Pool in a Developing Tidal Freshwater Marsh

Tidal marshes play an important role in the estuarine Si cycle. Dissolved silicon (DSi) is taken up by marsh diatom communities and by tidal marsh vegetation. Delivery of DSi back to the estuary after biogenic silica dissolution potentially increases the resilience of the estuary against harmful effects of DSi depletion events. Tidal freshwater marsh vegetation, often dominated by reed (Phragmites australis) has previously been hypothesized to contribute to the Si buffering function of tidal marshes, by dissolution of reed biogenic Si (BSi) into the soil pore water and consequent seepage of DSi to the estuary. In this study the Si pool in the vegetation of a restored tidal freshwater marsh was quantified using species-based cover-biomass relationships and Si analyses. The Si pool in the aboveground biomass increased from 1.2 to 6.5 t km−2 during the first 6 years of colonization by tidal freshwater marsh species. Our results indicate that young tidal freshwater marshes have a high potential to build up a large vegetation Si pool quickly, mostly due to colonization by species that have both high Si concentrations and high biomass production (e. g. P. australis). This Si pool in vegetation could act both as a long-term sink for Si along estuaries (should Si remain buried in the sediments) or as a short-term source for DSi (should Si be dissolved to DSi).

Network structures of fullerene-like carbon core/nano-crystalline silicon shell nanofibers as anode material for lithium-ion batteries

Fullerene-like carbon (FLC) nanoparticles were prepared by depositing soot of burning castor oil. FLC core/nano-crystalline silicon (nc-Si) shell nanofibers with network structures have been fabricated by electrospinning and plasma enhanced chemical vapor deposition techniques. The morphologies and structures of the materials were characterized using scanning electron microscopy, transmission electron microscopy, and micro-Raman spectroscopy. It was demonstrated that the FLC core/nc-Si shell nanofibers on nickel foam can be used as electrode for lithium-ion batteries without adding any binding or conducting additives. High reversible specific capacity of 1164mAhg−1 is retained after 50 discharge/charge cycles at a constant current density of 100mAg−1. The electrode delivers prolonged cycle life and enhanced rate capability compared to pristine nc-Si film. The improved electrochemical performance could be attributed to that the FLC core provides facile strain relaxation to accommodate the large Si volume expansion and shrinkage during lithium-ion insertion and extraction.

정보시스템 감리사례 분석을 통한 품질 향상 방안에 관한 연구

현재 조직의 성공적인 운영을 위해서 정보시스템의 중요성은 더욱 증가하고 있으며, 또한 정보시스템 구축에 대한 감리는 감리 의무화에 따라 더욱 확산되고 있다. 그러나 아직까지도 우리나라의 정보시스템 감리는 정보시스템의 다양한 위험에 제대로 대처하지 못하고 있으며, 각종 정보시스템 프로젝트에 대해 감리를 수행하면서 부실 사례가 종종 발생하고 있어 이에 대한 개선 대책이 절실히 필요한 실정이다. 이에 따라 본 논문에서는 국내 대형 SI업체에서 4년간 수행한 정보시스템 감리 프로젝트 및 위험발생 프로젝트 데이터를 중심으로 통계분석을 수행하여 정보시스템 구축 프로젝트의 품질향상을 위하여 개선된 검토항목을 제시하였고, 또한 이를 실제 정보시스템 프로젝트 사례에 적용하여 본 논문의 결과에 대한 실효성을 검증하였다. For the successful operation of the current organization, the importance of the information system is further increasing, and audit for the information system construction is also spreading according to the mandatory of information system audit. However our country's information system audit still does not deal with various risks and the improvement plan of it is desperately needed since bad practices are often happened while performing audit for the various information system projects. Therefore, this paper proposed improved review items for the quality improvement of information system construction by analysing data of information system audit projects and risk occurrence projects that are performed by the domestic large SI company during four years. In addition, this paper verified the effectiveness of the improved review items proposed in this paper by applying them to actual information system project examples.

A transimpedance amplifier for excess noise measurements of high junction capacitance avalanche photodiodes

This paper reports a novel and versatile system for measuring excess noise and multiplication in avalanche photodiodes (APDs), using a bipolar junction transistor based transimpedance amplifier front-end and based on phase-sensitive detection, which permits accurate measurement in the presence of a high dark current. The system can reliably measure the excess noise factor of devices with capacitance up to 5 nF. This system has been used to measure thin, large area Si pin APDs and the resulting data are in good agreement with measurements of the same devices obtained from a different noise measurement system which will be reported separately.

Radiation Treatment of T1-T2N0 Squamous Cell Carcinoma of the Glottic Larynx in the Modern Era

adjustments, the trends could be largely compensated with eNAL (SI margin 3.5 mm). Correlation between movements of the primary and nodal CTVs in SI direction was poor (r Z 0.15). For this reason, even with perfect on-line set-up corrections of the primary CTV (no residual errors), the required SI margin for the nodal CTV would be as large as 7 mm. In Left-Right (LR) and Anterior-Posterior (AP) directions, movements of the primary and nodal CTVs were largely correlated (r Z 071/0.64). Even with the two off-line protocols, required PTV margins in LR and AP directions were limited to 2-3 mm for both CTVs. SI motion correlation between the cervical vertebrae and the primary CTV was poor ((r Z 0.19). When using the vertebrae as reference structure in image guidance, the required SI margin around the primary CTV would be 7 mm, even with daily on-line repositioning. Conclusions: Without set-up corrections, laryngeal cancer patients showed large SI interfraction time trends in set-up of the primary tumor that could partially or almost fully be compensated with eNAL and daily on-line, respectively. Due to poor SI motion correlation of the primary tumor and the nodes, even perfect daily repositioning of the primary CTV required a 7 mm PTV margin around the nodes. Small nodal PTV margins would require an adaptive approach to correct for the non-rigid motion. Even with daily online corrections, the required SI PTVmargin around the primary CTVwould be as large as 7mm, when using the vertebrae as reference structure in image guidance. Generally applied 5 mm PTV margins in head and neck cancer were often inadequate for the studied laryngeal cancer patients. Author Disclosure: B. Heijmen: None. A. Gangsaas: None. E. Astreinidou: None. S. Quint: None. P. Levendag: None.

The reduction of charge recombination and performance enhancement by the surface modification of Si quantum dot-sensitized solar cell

Multiple exciton generation solar cell based on quantum dots has higher theoretical efficiency than single exciton generation solar cell. In this work, Si quantum dots with the diameter of 10nm were fabricated by the multi-hollow discharge plasma chemical vapor deposition and applied to the quantum dot-sensitized solar cell. In this cell, there was considerable electron recombination with redox electrolyte in the Si–TiO2 network because of large Si particle size. For the reduction of recombination and the enhancement of performance, a barrier layer was introduced. Zinc nitrate hexahydrate (Zn(NO3)2·6H2O) and zinc acetate dihydrate (Zn(CH3COO)2·H2O) were employed as precursors for surface modification. Consequently, short circuit current and open circuit voltage of the cells were increased by the surface modification with both precursors. The improvement was ascribed to the inhibition of electrons back transfer from TiO2 to the electrolyte by the barrier layer. This result clearly demonstrated that the surface modification with ZnO was advantageous for the performance enhancement.

Tunable ion-swelling for nanopatterning of macroscopic surfaces: The role of proximity effects

Ordered surface nanopatterns with different spatial periods and various characters were prepared on silicon surfaces by masked ion irradiation utilizing the local ion-swelling effect. Langmuir–Blodgett (LB) monolayers of hexagonally arranged Stöber silica particles as nanomasks were applied on large area Si substrates during Ar+ or Xe2+ exposure with different fluences. We show that the height and curvature of surface swelling patterns can be tuned by appropriate selection of the particle diameter, ion energy, and ion fluence. It is also revealed that the ion beam-induced anisotropic deformation of the silica mask can be exploited to tailor the surface geometry. We point that, having knowledge on the diameters and average spacing between the silica particles as extrinsic beam spreading factors, and considering the lateral straggling of the bombarding ions in the mask and in the substrate material as intrinsic beam spreading factors, a simple model of the radial fluence distribution can be applied to predict the main features of irradiation-induced surface patterns. The role of proximity effects in the potential use of this easy, fast, wafer-scale nanofabrication method is discussed.

Simplified process for dot sequential lateral solidification of sputtered amorphous silicon thin films

In this work we demonstrated an improved method to obtain large grain Si islands matrix with the use of dot sequential lateral solidification. Amorphous Si thin films were deposited on glass plates and Si wafers with thin oxide layer by magnetron sputter. Dot sequential lateral solidification (dot-SLS) was applied on the selected areas of the films by a 248nm excimer laser. The laser beam was patterned by a stainless steel mask. The setup is designed such that the dot-SLS process can be carried out by having the samples move against the laser beam and patterned mask in a uniform motion, which greatly simplified the dot-SLS process. Single crystalline Si grains with an average size of 10μm were obtained and further characterized by an optical microscope, scanning electronic microscope (SEM) and Raman spectrometer. The research work showed a simple method to achieve single crystalline Si islands matrix, which could be used as a seed layer to produce large grain sized Si films for high efficiency polycrystalline Si thin film solar cells and high performance flat panel displays.

SU‐C‐BRA‐02: Evaluation of 2D DIR from CBCT to 4DCT Projections as a Tool for IGART

Purpose: To demonstrate 2D parallelized DIR as a method to correct for anatomical changes of patient anatomy and respiratory motion. CBCT to simulated 4D‐CT projections using DIR can be used in real time for respiratory phase determination, patient setup or as a retrospective analysis to track inter‐ and intra‐fractional deformations. Methods: Ten phases of simulated 4DCT respiratory projections were individually registered to pulmonary CBCT projections using a modified 2D‐DIR demons algorithm implemented on GPUs. An automated global image‐preprocessing algorithm of the simulated projection was implemented to account for the relative local inter‐modality intensity mismatch. The deformation vector field intermodality congruence was inspected using bony structures, diaphragm position, and tumor position. A phase prediction matrix was constructed by choosing the lowest sum absolute value of the ten deformation vector fields generated by DIR. Results: For AP projections SI and tangential respective deformation maximum displacements were 4.8mm and 4.78mm with a mean displacement of 1.71mm +/− 1.17mm and 1.07mm +/− 0.94mm. For Lateral projections SI and tangential respective deformation maximum displacements were of 3.67mm and 3.07mm with a mean displacement of 0.6mm +/− 0.73mm and 0.72mm +/− 0.64mm. The phase prediction model performs better for AP projections than for lateral projections as lateral patient thickness shrouds respiratory motions. Conclusion: Respiratory motion can still be accurately reconstructed even in the presents of large bony structure deformations. The phase determination matrix nullifies respiratory deformation in the AP projections as SI and tangential maximum and mean deformations are nearly equal and respiration produces large SI motion. Larger non‐respiratory deformations typically occur in the AP projections as the couch helps maintain rigidity in lateral projections. Implementation of parallelized DIR increases spatial accuracy of the integration between multimodality imaging and as an automated tool to assess geometrical changes intra‐ and inter‐fractionally.

Heterepitaxial Growth of High Quality Germanium Layer on Si(001)for GOI Fabrication

High quality Ge layers on Si(001) have been achieved by two-step heteroepitaxial deposition method using reduced pressure chemical vapor deposition (RPCVD) system. The effect of in-situ hydrogen annealing is investigated. On large Si wafers, the epitaxial Ge layers with TDD less than 1×107cm-2 is obtained. And Raman results indicate that the Ge layers have about 0.17% tensile stress. After successful bonding of the epitaxial Ge layers on Si substrate to a SiO2 wafer, the 6 inch GOI is achieved by Smart-cutTM technology.

Development of large format Si(Li) detectors for the GAPS dark matter experiment

The General AntiParticle Spectrometer (GAPS) is a novel approach for indirect dark matter searches that exploits cosmic antideuterons. The GAPS detection method involves capturing antiparticles into a target material with the subsequent formation of an excited exotic atom. The exotic atom decays with the emission of atomic X-rays and charged particles from nuclear annihilation, which uniquely identifies the captured antiparticle. We are currently developing the lithium-drifted silicon (Si(Li)) detector for the GAPS flight experiment. In this paper, we describe the diagnostic tests conducted on three prototype Si(Li) detectors and the noise model to characterize each detector. The GAPS prototype flight, preparatory for a long duration balloon flight from Antarctica in 2016–2017, is scheduled for launch from Japan in summer 2012.

Origin of omphacitites from the Nishisonogi metamorphic rocks, western Kyushu, Japan: comparison with jadeitites

Two types of omphacitites are distinguished in ultramafic melanges that are intercalated with epidote–blueschist facies schists of the Nishisonogi metamorphic rocks in western Kyushu, Japan. One is an omphacitite layer in a metabasite block, and the other is an omphacitite lens in an albitite block. These omphacitites are principally composed of omphacite with minor amounts of winchite/magnesiohornblende, epidote, albite and titanite. Although the petrographic features of both types are similar, the omphacitite layer is depleted in light rare earth elements (LREE; La, Ce and Nd) compared with the omphacitite lens. In the case of jadeitites, those interpreted as being formed by direct precipitation from aqueous fluids are LREE-depleted, while those interpreted as being formed by metasomatic replacement from protoliths are LREE-enriched. Thus, by analogy, the omphacitite layer may have directly precipitated from aqueous fluids, and the omphacitite lens may be metasomatic in origin. The omphacitite layer has amphibole-rich selvages, which are likely formed by the reaction between the omphacitite-forming fluid and the host metabasite. Mass-balance analysis using the isocon method indicates that the formation of the selvages involves additions of large ion lithophile elements (LILE; Rb, K and Ba), Na and Si to the host metabasite. These components were likely introduced via fluid infiltration. Although the source of the omphacitite-forming fluid is not clear, the LILE-rich composition suggests participation of fluids derived from metapelitic rocks.

Cost-Effective 1.25-Gb/s CMOS Receiver for 50-m Large-Core SI-POF Links

This letter proposes a new analog front end for short-reach high-speed optical communications that compensates the limited bandwidth of 1-mm step-index polymer optical fiber (SI-POF) transmission systems. In particular, the front end has been fabricated using a cost-effective digital 0.18- complementary metal-oxide-semiconductor (CMOS) technology and fed with only 1 V. The prototype contains a transimpedance amplifier, a continuous-time equalizer, and an output driver. Experimentally, we have obtained 1.25-Gb/s transmission for a simple nonreturn-to-zero modulation in an optical link composed of 50 m of SI-POF and a large area Si PIN photodetector.