The results of an experimental study of the interband transitions of the cuprous halides, CuI and CuBr, are reported. High-resolution, low-temperature, near-normal incidence reflectance and thermal modulated reflectance spectra were studied over the range 3-10 eV. Thin-film samples, prepared by vacuum deposition, and a single-crystal sample of CuI were measured. Spectral structures are assigned to specific interband transitions in the Brillouin zone on the basis of splittings and temperature shifts, and compared with the predictions of the Phillips-Van Vechten ionicity theory of energy-gap trends in zinc-blende-structured isoelectronic sequences.

• Received 9 July 1979

DOI:https://doi.org/10.1103/PhysRevB.21.2562