PIEZOREFLECTANCE OF DILUTE ALPHA-PHASE AG-IN ALLOYS

The fractional change in reflectivity due to strain RR of evaporated film samples of four silver-indium alloys was measured in the energy range 2.5-4.5 eV. The films had indium concentrations of 0.4, 1.6, 3.3, and 5.0 at.%. A Kramers-Kronig inversion of RR yielded the change, due to strain, of the phase shift of the reflected electric field. The strain-induced changes of the real and imaginary parts of the complex dielectric constant, 1 and 2, were calculated. Interpretation of the structure in 2 of silver and the four alloys yielded the following conclusions. (a) The structure in 2 at 4.06 eV in silver is due to the L2L1 (Fermi surface to conduction band) transition and not to the L3L2 (d band to Fermi surface) transition as previously suggested. (b) The L2L1 band gap in silver is 4.15 eV and decreases to about 3.7-3.8 eV in the 5.0% indium alloy. (c) Indirect transitions contribute to 2 and 2 below the direct L2L1 transition energy in the silver-indium alloys. © 1969 The American Physical Society.