Surface Energy of Germanium and Silicon

Surface energy is one of the most fundamental parameters of a solid since it depends directly on the binding forces of the material. Indeed, it is a measure of the work necessary to separate a material into two parts along a plane. Very few measurements have been made of this quantity and these by indirect means, because of difficulties of measurement and interpretation. This report deals with a direct measurement of specific surface energy of Ge and Si made by the cleavage technique. By measuring the force just necessary to move a crack "in reversible fashion" the surface energy can be obtained. The measured value for the {111} planes of Ge and Si are 1060 ergs/cm2 and 1230 ergs/cm2. From these measured values the energy of the planes {100} and {110}can be estimated. They are: Using the measured value of specific surface energy, assuming this is due to the appropriate number of broken , the bond strength of Ge and Si was obtained as ; .