ABOUT THE MEASUREMENT OF ABSOLUTE ISOTROPIC SURFACE STRESS OF CRYSTALS

Some recent publications report measurements of the curvature of thin asymmetric sheets and deduce the difference of surface stress (s(1) - s(2)) of both its faces 1 and 2 using a simple formula due to Stoney. An exact formulation gives a relation where (s(1) + s(2)) enters also. It is shown here how, for thin sheets, (s(1) - s(2)) and (s(1) + s(2)) can be measured and therefore the absolute surface stresses s(1) and s(2). For thicker sheets, only (s(1) - s(2)) can be measured. Two experimental methods for measuring the absolute surface stresses are proposed.