The formation behavior of grown-in defects which are considered to be oxygen precipitates formed during CZ-Si crystal growth, was investigated by means of infrared light scattering tomography. The following results were obtained. (i) The density of the IR light scattering defects decreases with a reduction in the crystal pulling rate. (ii) The defects are not formed just after solidification, but they grow to a size detectable by LST during cooling to about ll00~ (iii) The defect density decreases by slow cooling in the temperature range from to 1500 to 1000~ while their size increases. The formation mechanism of the defects was qualitatively discussed from the point of view of the interaction between oxygen atoms and point defects by a consideration of the free energy change and the critical radii of nuclei for oxygen precipitation. It was suggested that the formation of the defects depends on the vacancy concentration. In the case of a constant vacancy concentration, their density and size are determined by the cooling rate in the temperature range from 1150 to 1000~
We introduce a local measure of the quality of a trial wave function: the local variance. Using this tool we examine the pair function often adopted to construct wave functions for small helium clusters and apply it to a wave function for 4 He2 using the TTY interaction potential. Our analysis shows that this commonly employed functional form should be improved in the short-range region. We introduce a new model based on the short-range behaviour of the exact ground-state solution of a Morse potential. The resulting compact trial wave function for 4 He2 recovers 98% of the exact binding energy with only six variational parameters.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.