Partial melting mechanisms of embedded nanocrystals

Abstract

Understanding the melting mechanisms of nanocrystals embedded in solids is of great current interest since both the synthesis and modification of such systems frequently involve the use of high temperatures. Using molecular-dynamics computer simulations we study the melting mechanisms of Cu, Ag, and Au nanoclusters embedded in metal matrices and Si nanocrystals in amorphous silica. The results show that nanocrystals embedded in a solid bulk material with a higher melting temperature exhibit complex melting behavior and can even, in the same system, exhibit four distinct stages prior to full melting of the system.

Amorphization of Ge nanocrystals embedded in amorphous silica under ion irradiation

“…In previous studies, it has been shown that the properties of nanocrystals may significantly vary from the properties of the same crystals in the bulk phase. For instance, the melting point of crystal structure of the nanosize can be significantly higher or lower than that of the same element or compound in its conventional phase depending on the nature of surrounding matter [4][5][6][7][8][9][10][11]. High-dose ion irradiation of elemental metal nanoclusters leads to the amorphization of their crystal structure, while it is known that elemental bulk metals can not be amorphized [12].…”

Amorphization of Ge and Si nanocrystals embedded in amorphousSiO2by ion irradiation

“…For instance, nanocrystals can melt at a temperature higher or lower than their bulk counterparts. [1][2][3] The ionization energy, electron affinity, 4 and photoluminescence lifetime 5 for elemental semiconductor nanocrystals can not only be different from bulk but can also be strongly size dependent.…”

Ion–solid interactions at the extremes of electronic energy loss: Examples for amorphous semiconductors and embedded nanostructures

“…Voids form in the HDL phase and are potentially frozen in when the cooling rate is sufficiently rapid. Given the ion track is nanometers in width and can cool by heat conduction in two dimensions, rapid cooling is possible and several MD studies have shown that even with only phonon heat conduction, tracks can cool on time scales of the order of 100 ps [6,[16][17][18][19]. This however cannot explain the peculiar bow-tie shape of the voids, as the minimisation of the surface energy should lead to spherical voids, or considering the asymmetric cooling in an ion track in two dimensions, possibly ellipsoidal voids.…”