OBSERVATION OF UMKLAPP AND SURFACE BANDS IN PHOTOEMISSION EXPERIMENT ON II-VI MATERIALS - A STUDY OF CD0.6HG0.4TE

Normal and off-normal photoemission are performed in the 16-27 eV rang e on Cd0.6Hg0.4Te mixed crystal. The umklapp bands, well recognized on normal incidence energy distribution curve, can be followed in off-no rmal data, with continuous variations not previously observed. A tight binding calculation of the energy dispersion of the umklapp bands con firms that most secondary emissions are in fact related to umklapp ban ds. The surface states appear partly masked by these bulk derived umkl app bands. Only one surface state, in an inner gap of the valence band , appears distinct from other bulk features, which indicates that some of the previously mentioned experimental surface states in II-VI comp ounds should be revised.