Modified Timoshenko formula for bending of ultrathin strained bilayer films

Mechanical bending of nanoscale thin films can be quite different from that of macroscopic thick films. However, current understanding of mechanical bending of nanoscale thin strained bilayer films is often limited within the Timoshenko model [Timoshenko, J. Opt. Soc. Am. 11, 233 (1925)], which was originally derived for macroscopic thick films. Here, we derive a modified Timoshenko formula by including the prominent effect of surface stress played in the nanofilms, which gives a much better agreement with the experiments than the classical formula. (c) 2008 American Institute of Physics.