HALL-MOBILITY IN DC-SPUTTERED BI2SR2CACU2O8+DELTA FILMS AS A FUNCTION OF IN-SITU CONTROLLED OXYGEN-CONTENT

DC-sputtered Bi2Sr2CaCu2O8+delta thin films were in-situ prepared from the underdoped (T-c = 76K) to the overdoped (T-c = 60K) state by varying the oxygen flow during the sputtering process. For reference purposes the oxygen content of the polycrystalline bulk material was varied over the same range. The absolute oxygen content of the polycrystalline material was determined by iodometric titration. Combining this with the c-axis length of the polycrystalline material and the films, we have established the electronic T-c vs. delta phase diagram of the films as a function of the absolute oxygen content. The inverse Hall mobility of the films follows a simple temperature dependence mu(-1) = a + b.T-m in the normal state. At low oxygen concentration the exponent is m congruent to 2 indicating fermion-fermion scattering of the holes. At higher doping the exponent m is continuously decreasing towards m approximate to 1. This shows a change of the dominant scattering mechanism of the holes. For the sample with the highest T-c the different scattering contributions are of comparable magnitude m congruent to 1.7. We found this exponent to be a general feature of high-T-c compounds, such as Bi-2212, Y-123 and La-214.