Electronic properties of hole- and electron-doped T'-, T*-, and infinite-layer-type high-Tc cuprates.

We compare the electronic structure of [ital n]-type and [ital p]-type dopable high-[ital T][sub [ital c]] cuprates, namely the hole-doped Nd[sub 1.4]Ce[sub 0.2]Sr[sub 0.4]CuO[sub 4[minus][delta]] ([ital T][sup *]) system as well as the electron-doped Nd[sub 2[minus][ital x]]Ce[sub [ital x]]CuO[sub 4[minus][delta]] ([ital T][prime]) and Sr[sub 0.85]Nd[sub 0.15]CuO[sub 2[minus][delta]] ( infinite-layer'') systems. Investigations were done mainly by means of core-level and valence-band photoemission spectroscopy. Also we performed auxiliary measurements of Hall effect and magnetic susceptibility. From the investigations on the Cu-O layers we propose that one criterion for electron dopability in high-[ital T][sub [ital c]] cuprates is a comparatively high value of the Cu 3[ital d] Coulomb interaction [ital U][sub [ital d][ital d]]. This is concluded from model calculations on core-level and valence-band spectra. Also the superconducting infinite-layer compound Sr[sub 0.85]Nd[sub 0.15]CuO[sub 2[minus][delta]] exhibits (besides a remarkably low Cu-O hybridization) this enhanced value of [ital U][sub [ital d][ital d]]. For the rare-earth layers of [ital T][prime] and [ital T][sup *] we find small but characteristic differences in the electronic properties (Nd-O-hybridization and charge-transfer energy), which can be attributed to structural differences.