Two devices have been constructed for the development of biaxial stresses and the study of deformation potentials on thin layers. In the first device hydrostatic pressure was employed to develop a two-dimensional stress environment on thin silicon wafers. The deformation of the plates was found to be related to the third root of the pressure applied, in good agreement with theory. The second apparatus used a central force for the bending of the wafer, and the stresses, as detected from the frequency shift of the silicon phonon line in the Raman spectra, were confined to a small area of the plate. In both devices and analytic relation between the radius of curvature at the centre of the wafer and the stresses developed was established.
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