Infrared Absorption in Single-Crystal Stannic Oxide: Optical Lattice-Vibration Modes

Abstract

The ir reflection spectrum of single-crystal stannic oxide has been observed at room temperature in the region 2000 to 100 cm−1, and analyzed by classical dispersion theory to give values for the transverse and longitudinal optical-mode frequencies. For the cassiterite structure, four lattice-vibration modes may interact with infrared radiation, three of these with radiation polarized perpendicular to the c axis, and the remaining one with radiation polarized parallel to the c axis. The oscillator frequencies found for the best fit to the experimental reflection curves are: E⊥c, 243, 284, and 605 cm−1; E ∥ c, 465 cm−1. Low-frequency dielectric constants are estimated from this analysis to be 13.5 and 9.58 for E⊥c and E ∥ c, respectively, which are about half the literature values. The E⊥c value was confirmed directly in a substitution bridge measurement yielding 15±1 for the frequency range 102 to 106 Hz.