Surface stress and the normal mode of vibration of thin crystals :GaAs

The normal mode of vibration of (111) GaAs wafers with a thickness below about 15 μm was found to depend strongly on the surface preparation and on the ambient atmosphere. This dependence was attributed to effects directly related to the surface stress σs. It was shown that σs can be evaluated from the natural frequency of vibration. The values of σs, in the 〈110〉 direction, for etched and unetched (111) GaAs wafers in room atmosphere were found to be 325 and 570 dyn/cm, respectively. It was further demonstrated that surface stress transients due to the adsorption processes (adsorption transients) can be determined by corresponding changes in the natural frequency of vibration.