Application of 7N In as secondary cathode for the direct current-glow discharge mass spectrometry analysis of solid, fused high-purity quartz

Direct current glow discharge mass spectrometry with an indium-based secondary cathode technique is used to analyze solid, nonconducting, fused high-purity quartz regarding metallic impurities of relevance to the solar industry. Details of the analytical routines are presented. In this work, the secondary cathode design and glow discharge conditions are optimized beyond the commonly applied practices. In addition, relative sensitivity factors (RSFs) for these optimized conditions are established and compared to previously published results. The results indicate that the technique enables stable measurements with detection limits down to the part per billion (ppb) range.publishedVersio

Depth profiling at a steel-aluminum interface using slow-flow direct current glow discharge mass spectrometry

Direct current glow discharge mass spectrometry (dc-GDMS), which relies on sector field mass analyzers, is not commonly used for depth profiling applications because of its slow data acquisition. Nevertheless, dc-GDMS has good reproducibility and low limits of detection, which are analytical features that are encouraging for investigating the potential of dc-GDMS for depth profiling applications. In this work, the diffusion of traces of chromium and nickel was profiled at the interface of a steel-aluminum bilayer using a new sensitive dc-GDMS instrument. The depth profile of the non-treated sample was compared with that of a heat-treated specimen at 400°C for 30 min. Scanning electron micrographs, energy dispersive X-ray spectroscopy (EDS), and electron probe microanalysis (EPMA) were used to study the diffusion process. The results of the study show that both chromium and nickel are enriched at the steel-aluminum interface, with higher concentrations of both elements for the heat-treated specimen. Two peaks for both chromium and nickel were clearly present at the interface, with a high concentration of chromium in the aluminum layer. This observation is likely a consequence of elemental diffusion from the interface towards the aluminum layer. The presence of the third layer, steel beneath the aluminum layer, might also have contributed to this observation.acceptedVersio

Investigation of pinholes in Czochralski silicon ingots in relation to structure loss

acceptedVersio

Effect of Hot Rolling on Grain Refining Performance of Al–5Ti–1B Master Alloy on Hot Tearing on Al–7Si–3Cu Alloy

It has been known experimentally that TiAl3 acts as a powerful nucleant for the solidification of aluminum from the melt; however, a full microscopic understanding is still lacking. To improve microscopic understanding, hot rolling technique has been performed to the Al–5Ti–1B alloy and the effect of shape and size of the particles on grain refinement has been studied. The effect of hot rolling of Al–5Ti–1B master alloy on its grain refining performance and hot tearing have been studied by OM, XRD, and SEM. Hot rolling improves the grain refining performance of this master alloy, which is required to reduce hot tearing in Al–7Si–3Cu alloy. The improvement in grain refining performance of Al–5Ti–1B master alloy on rolling is due to the fracture of larger TiAl3 particles into fine particles during rolling. The presented results illustrate that the morphology of TiAl3 particles alter from the plate-like structure in the as-cast condition Al–5Ti–1B master alloy to the blocky type after rolling due to the fragmentation of plate-like structures. The grain refining response and effect on hot tearing of Al–7Si–3Cu alloy have been studied with as-cast and rolled Al–5Ti–1B master alloys. The results display hot-rolled master alloys revealing enhanced grain refining performance and minimizing hot tear tendency of the alloy at much lower addition level as compared to as-cast master alloys

Statistical Analysis of Structure Loss in Czochralski Silicon Growth

In Czochralski monocrystalline silicon growth, structure loss (SL) is the loss of the mono-crystalline structure. It represents a significant loss of productivity. In this work, this phenomenon is investigated by statistical analysis of production data of roughly 14000 ingots produced over a year of time at NorSun factory in Årdal, Norway. It is found that ingots with structure loss typically have lower heater power and temperature fluctuations than ingots without structure loss after four hours of body (ca. 240 mm). Particularly, ingots without manual adjustment by furnace operator have significantly higher frequency of structure loss than ingots for which the operator has increased the temperature one or more times. Most ingots with structure loss are also found to have a higher pull speed on average than ingots without structure loss, and that there is a threshold below which no ingots had structure loss. A binary logistic regression was used for classification of ingots with and without structure loss and 30% of the data was used to comparison of predictions of the model. Using only the standard deviation of the temperature fluctuations around a moving average provided a prediction accuracy of 99.6%, for ingots that have passed six hours of body (ca. 360 mm).publishedVersio

Temporal stability of a-Si:H and a-SiNx:H on crystalline silicon wafers

publishedVersio

Statistical analysis of structure loss in Czochralski silicon growth

In Czochralski monocrystalline silicon growth, structure loss (SL) is the loss of the mono-crystalline structure. It represents a significant loss of productivity. In this work, this phenomenon is investigated by statistical analysis of production data of roughly 14000 ingots produced over a year of time at NorSun factory in Årdal, Norway. It is found that ingots with structure loss typically have lower heater power and temperature fluctuations than ingots without structure loss after four hours of body (ca. 240 mm). Particularly, ingots without manual adjustment by furnace operator have significantly higher frequency of structure loss than ingots for which the operator has increased the temperature one or more times. Most ingots with structure loss are also found to have a higher pull speed on average than ingots without structure loss, and that there is a threshold below which no ingots had structure loss. A binary logistic regression was used for classification of ingots with and without structure loss and 30% of the data was used to comparison of predictions of the model. Using only the standard deviation of the temperature fluctuations around a moving average provided a prediction accuracy of 99.6%, for ingots that have passed six hours of body (ca. 360 mm).publishedVersio

The effect of preliminary heat treatment on the durability of reaction bonded silicon nitride crucibles for solar cells applications

Silicon nitride crucibles have the potential to replace silica crucibles and reduce the cost of silicon crystallization because of their reusability potential. Till date, crucibles’ heat treatment before each use is a prerequisite to achieve non-wetting conditions that is needed to facilitate the ingot release and hence enable reusability. Yet, no studies have examined the heat treatment influence on the crucibles’ durability. The present investigation focuses on the crucibles’ heat treatment and its impact on the crucibles’ lifetime. Repeated heat-treatments of silicon nitride crucibles in the air at above 1100 °C leads to crucible fracture. Therefore, this study identifies the cause and the mechanism of such failures by applying different heat treatment procedures in the air. The mass gain and the oxidation rates of the crucibles at different temperatures are measured via Thermogravimetry (TG) and Differential Thermal Analyzer (DTA). The results show that the porosity and phase distribution along the crucible wall thickness, play a key role in the crucible’s behavior during oxidation. Moreover, excessive internal oxidation in the tested crucibles results in severe thermal stresses which cause cracking during cooling.publishedVersio

Kinetics of silicon nitride coatings degradation and its influence on liquid infiltration in PV silicon crystallization processes

Safe implementation of reusable crucibles in the silicon PV industry requires a thorough understanding of the reactions in the system to avoid liquid infiltration and crucible failure at high temperatures. Typically, an oxidized Si3N4-coating layer is applied to the crucibles to avoid wetting. During melting, the coating undergoes a transition in its wettability behavior as a result of oxide depletion. However, much uncertainty still exists about undergoing reactions and their effect on the coating depletion, and hence the wetting kinetics. Here we report on the coating's oxygen depletion mechanisms by applying a novel coating method to avoid conventional oxidation as it causes severe degradation of non-oxide crucibles. By adding colloidal silica to the silicon nitride coating, we (i) control the oxygen concentration in the coating, (ii) avoid the crucible degradation, and (iii) eliminate the pre-oxidation step. Furthermore, a quantification of the coating's oxygen content effect on the depletion rate was presented via an analytical model. These results provided insight into how the coating depletion can hinder the liquid infiltration by forming and stabilizing silicon oxynitride in the coating as evidenced by Raman mapping and thermodynamic calculations. The difference between the rates of liquid infiltration and oxygen depletion was also elucidated in detail

Application of 7N In as secondary cathode for the dc‐GDMS analysis of solid, fused high‐purity quartz

Direct current glow discharge mass spectrometry with an indium-based secondary cathode technique is used to analyze solid, nonconducting, fused high-purity quartz regarding metallic impurities of relevance to the solar industry. Details of the analytical routines are presented. In this work, the secondary cathode design and glow discharge conditions are optimized beyond the commonly applied practices. In addition, relative sensitivity factors (RSFs) for these optimized conditions are established and compared to previously published results. The results indicate that the technique enables stable measurements with detection limits down to the part per billion (ppb) range