OPTICAL-DETECTION OF THE SUPERCONDUCTING PROXIMITY EFFECT - RAMAN-SCATTERING ON NB INAS/

Raman scattering on InAs coated with 60 to 100 Angstrom thick Nb films (T-c = 2.5 to 5K) is studied. The Nb films, sputtered onto in-situ io n-etched n(+)-InAs (1.2x10(19)cm(-3)) are flat to similar to 5 Angstro m. The low-frequency coupled plasmon-phonon Raman mode (L_) associated with bulk InAs is centered at 221cm(-1). The forbidden LO phonon at 2 37cm(-1), associated with the surface charge accumulation region (CAR) , is observed because the thickness of the surface CAR is less than th e Thomas-Fermi screening length. As the temperature is reduced below T -c the magnitude of the LO phonon mode intensity, relative to that of the L_ mode, increases by more than 40%.