We use x-ray absorption (XAS) total electron yield measurements to investigate strain-induced splitting of the conduction band minimum in very thin Si layers and membranes. We use synchrotron generated X rays with variable energy to excite electrons from the 2p core level of strained Si to empty electronic states in the conduction band minima. The Auger electrons emitted in the relaxation process make the method extremely surface sensitive and reflect the position and density of states of the conduction band. We determine these parameters for elastically strained Si nanomembranes and strained-Si-on-insulator. We demonstrate significant lateral nonuniformity in the strain in strained-Si-on-insulator, while the strain is uniform on strain sharing nanomembranes. Low-energy electron microscopy measurements support this conclusion.
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