Heat-capacity comparison among the nanocrystalline, amorphous, and coarse-grained polycrystalline states in element selenium

Abstract

Nanocrystalline element selenium (nc-Se) samples were synthesized by completely crystallizing a meltquenched amorphous selenium ($a$-Se). Heat capacities (${C}_{p}$) of the nc-Se (with a mean crystallite size of 10 nm), a fully relaxed $a$-Se, and a coarse-grained polycrystalline Se were experimentally determined in a temperature range of 225-500 K. Measurement results show that there is no pronounced difference between the ${C}_{p}$ values of the nc-Se and the $a$-Se below 250 K. Heat capacities of the nc-Se are found to be only about 2% higher than those of the coarse-grained polycrystalline selenium. The ${C}_{p}$ enhancement for the nc-Se, which is much lower than those reported in other nanocrystalline elements, is discussed in terms of the grain-boundary configurations in the nanostructures.