Papers by Keyword: Iron Contamination

Abstract: Accelerating the pace of Nuclear Power Plants construction is critical to the Growth of Indian Economy. It calls for timely and First Time Right manufacturing of various Reactor Equipment. This paper captures the experience of Godrej Precision Engineering Division in successful realization of Calandria, in record time, with First Time Right Quality adhering to very demanding and stringent requirements.

Abstract: In this work laboratory scale multicrystalline silicon ingots were grown which have been intentionally contaminated with iron in the range between 10 to 400 ppmw by adding FeSi2 to the silicon feedstock. It is shown that an iron contamination at these high levels does not result in a structural breakdown of the columnar grain growth regime because constitutional supercooling could be avoided by strong mixing of the melt in the present crystal growth experiments. The minority carrier lifetime mappings are dominated by the iron contamination and show the distribution of the impurity over the ingot height. The measured values of the specific electrical resistivity show a significant drop from 40 to below 20 Ωcm for a contamination level of 10 ppmw Fe probably due to interactions of iron with thermal donors. At higher contamination levels the specific resistivity increases significantly with increasing iron concentration compared to the 10 ppmw ingot. Above 400 ppmw iron the specific resistivity drops below the initial value for nominally iron free material. These results indicate that interstitial iron shows a donor-like behavior in multicrystalline silicon and precipitated iron decreases the specific resistivity.

Abstract: It is shown that the X-ray beam induced current method (XBIC) can be realized at the laboratory X-ray source using the polycapillary x-ray optics. The images of iron contaminated grain boundaries in multicrystalline Si are obtained. It is shown that the grain boundary XBIC contrast is 2-3 times smaller than the EBIC one. A simulation of XBIC and EBIC contrast values for two-dimensional defects is carried out and a good correlation between the experimental and calculated values is obtained. The dependence of grain boundary XBIC contrast on the X-ray beam width is calculated.

Abstract: Silicon samples doped with gallium and intentionally contaminated with iron have been studied by means of electron beam current (EBIC), capacitance voltage (CV) and deep level transient spectroscopy (DLTS) methods. Reverse bias anneal (RBA) treatments at temperatures of 390-420K were used to move hydrogen and dissolved iron atoms away from the surface. A new procedure was developed to find dislocations lying on desirable depth from the surface and to analyze the depth distribution of their recombination contrast. Iron contaminated dislocations do not noticeably change their recombination activity when kept in an electrical field as high as 104 V/cm at 420K for several hours. This implies a tight binding of iron atoms at dislocations. The binding energy of iron with dislocations seems to be much larger than for Fe-Ga and H-Ga pairs. Low temperature hydrogenation of iron contaminated dislocations does not produce any passivation effect. In opposite, the recombination activity of the dislocations significantly increases after RBA treatment.