Specific Surface Free Energy of Ruby Thin Film Grown on Sapphire Single Crystals Studied by Contact Angle of Liquid Droplet

Abstract

Ruby thin film was grown on sapphire substrate by evaporation method of MoO3 flux. Small amount of Na2CO3 was added in order to decrease the evaporation rate of flux. The contact angles of liquids and crystal surfaces were measured for water and formamide droplets, and the specific surface free energy of each face of the crystal was calculated using Fowkes approximation and Wu's mean equations. The growth hillocks on the synthesized thin film were observed. The addition of Na2CO3 incrased the density of hillocks and the specific surface free energy was larger for the ruby thin film, which has larger number of hillocks.