Analysis of structural transformations and fluctuation effects in the nanosized nickel films in the vicinity of the melting point

Abstract

The effect of heating temperature on the structure of the nickel films with an original thickness of 20 nm that are deposited on silicon-oxide substrate (the thickness of the thermally grown silicon oxide SiO₂ is about 1 μm) is studied using the scanning probe microscopy. An increase in the temperature causes a decrease in the mean thickness of the Ni film from the original thickness h = 20 nm to 18 ± 2 nm at a temperature of 737 K and 15 ± 2 nm at a temperature of 752 K. The thickening of the film is interpreted with allowance for the heterogeneous melting. The voltage jumps across the film sample in the vicinity of the melting point under slow heating and constant current flow through the sample are interpreted. In particular, the primary fluctuations lead to a decrease in the nickel film thickness due to the formation of drops from the liquid layer on the film surface and, hence, significant positive fluctuations of the resistance (or voltage jumps across the sample). Irreversible variations in the properties of thin metal films upon heating below the melting point are interpreted.