Variations in atomic structure of liquid bismuth clusters

A large number of elemental and compound semiconductors in bulk form become metallic upon melting due to changes in the local atomic structure occurring in the transition from the solid to the liquid state. We report studies of the vibrational properties of liquid Bi clusters that suggest that for the smaller sizes this atomic structure transition does not occur. Using interference enhanced Raman spectroscopy, in situ studies of bismuth ultrathin films, supported on weakly interacting carbon substrates, have been performed. Changes in the vibrational spectra with liquid cluster size have been correlated with ex situ transmission electron microscopy to estimate a critical size below which densification of the structure does not occur. For various models this yields clusters of diameter in the range of {~}45--75 {}.