| Summary: | 碩士 === 國立交通大學 === 電子物理系所 === 96 === The electronic structures of the ultrathin metal films on the semiconductor has been investigated by high resolution angle-resolved photoemission. In this thesis, the electronic structures of Ag/Ge(111) and of Pb/Ge(111) are studied. Ag/Ge(111) thin films are prepared at the thickness ranging 5-18 monolayers and the subband dispersions of quantum well states have been determined by angleresolved photoemission. The enhanced effective masses of the subbands for decreasing film thickness has been observed in some other systems. This behavior is also observed in Ag/Ge(111) system. An increased in-plane affective mass at the zone center at a small film thickness is observed; the trend follows closely a 1/N dependence. This can be attributed to a kinetic constraint for standing wave formation governed by a momentum-dependence phase shift function.
Lead deposits on Ge(111) have received a large amount of attention and the electronic structure of the (rt3 × rt3)R30 reconstruction was reported. When the highly-doped n-type Ge(111) is used, the band structures are totally different from those in the previous reports. Near the zone center, the band dispersion reflects the valence band edges of Ge including the heavy-hole, light-hole, and split-off hole bands. Both spin-orbit splitting bands and non-spin-orbital splitting bands are observed. A new surface state band centered at k-bar emerges at T = 120 K while no phase transition is observed by LEED pattern.
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