ELECTRON-SPECTROSCOPY FOR (001)BI2SR2CAN-1CUNO2N- COMPARATIVE-STUDIES(4(N=1,2) )

Clean (100) surfaces of Bi2Sr2CaCu2O8 (T(c) congruent-to 80 K) and Bi2 Sr2CuO6 (T(c) less than or similar to 6.5 K) crystals were investigate d by LEED, UPS, XPS, LEELS and Auger techniques at T almost-equal-to 2 0-1000 K It is found that both 2212 and 2201 crystals demonstrate very similar properties: (i) there is 5 x 1 superstructure rather stable i n the whole investigated temperature range; (ii) the ground state char ges are close to Bi3+, Sr2+, Cu2+ and O2-; (iii) normalized UPS signal s (HBARv = 21.2 eV) due to Cu 3d-O 2p occupied states are practically coinciding in the range from the Fermi energy E(F) down to E(F)-4 eV a t the energy resolution of 0.05 eV. It is argued that at this energy r esolution there is no evident correlation between the effective densit y of states N(E(F)) and the T(c)-values for the investigated crystals.