Raman scattering on InAs coated with 60 to 100Å thick Nb films (Tc = 2.5 to 5K) is studied. The Nb films, sputtered onto in-situ ion-etched n+-InAs (1.2 × 1019cm-3) are flat to ~5Å. The low-frequency coupled plasmon-phonon Raman mode (L-) associated with bulk InAs is centered at 221cm-1. The forbidden LO phonon at 237cm-1, associated with the surface chargeaccumulation region (CAR), is observed because the thickness of the surface CAR is less than the Thomas-Fermi screening length. As the temperature is reduced below To. the magnitude of the LO phonon mode intensity, relative to that of the L- mode, increases by more than 40%.
ASJC Scopus subject areas
- Physics and Astronomy(all)