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Abstract: Melting behavior of as-deposited and recrystallized indium nanocrystals is studied using reflection high-energy electron diffraction in its transmission mode. Indium films with mean thickness ranging from 1.5 to 10 monolayers (ML) deposited on highly oriented graphite at different substrate temperatures are studied. Atomic force microscopy is used to study the crystal size and morphology of the as-deposited and recrystallized nanocrystals. As-deposited films are found to form shallow nanocrystals with a flat top surface of different shapes, while the recrystallized nanocrystals are formed in the more rounded polyhedral shape. The change in the diffraction pattern intensity with temperature is used to probe the melting of the nanocrystals. The melting point is found to be lower than that of the bulk for both types of films and extends over a temperature range due to nanocrystal size distribution. The as-deposited films show an end melting point nearly equal to that of the recrystallized films except for the 1.5-ML film which shows an end melting point ∼10 K lower than the recrystallized film. The deposition temperature is found to have a significant effect on the end melting point of as-deposited nanocrystals, while having a negligible effect on the end melting point of recrystallized nanocrystals. [Copyright &y& Elsevier]

Melting and solidification of indium nanocrystals grown on (002) highly oriented graphite is studied by reflection high-energy electron diffraction operating in a transmission mode through the outer shell of the nanocrystals. When recrystallized from the melt, evaporated indium grows as an ensemble of nanocrystals with particle size distribution that depends on the mean film thickness. Films with mean thickness from 0.5 to 34 ML are investigated. The intensity change of the diffraction pattern with temperature is used to probe the melting and solidification of the nanocrystals. The melting of indium nanocrystals starts at temperatures below the bulk melting temperature, depending on the size distribution of the nanocrystals. Melting continues over a temperature range extending up to that of bulk melting. The liquid skin model of melting and the homogenous melting model are shown to agree with the melting point size dependence. However, line profile analysis of the diffraction pattern shows a reduction in the crystalline volume within the probed shell at high temperatures. This indicates the formation of a liquid layer surrounding the nanocrystals and supports the liquid skin model. All films show supercooling by an amount that increases with the mean film thickness up to 6 ML and remains constant for films with larger mean thickness. [Copyright &y& Elsevier]