Density and structure of undercooled molten silicon using synchrotron radiation combined with an electromagnetic levitation technique

X-ray diffraction and density measurements have been simultaneously performed to investigate the atomic structure of molten silicon in the undercooled temperature region with the use of an electromagnetic levitation technique. The density was obtained from the levitated sample shape by a non-contact method based on an image analysis technique. From structural analysis of the undercooled molten silicon, the first nearest neighbor coordination number and interatomic distance were determined to be about 5 and 2.48 Å, respectively. There are no temperature dependence of both the first nearest neighbor coordination number and interatomic distance, but a small change observed on the side of the first peak with the structure factor in the temperature range of 1550–1900 K. From these results, we conclude that the short-range order based on tetrahedral bonds of the undercooled molten silicon did not change with the degree of undercooling, however, the medium-range order was changed by the degree of undercooling.