Controlling the carrier concentration of the high temperature superconductor Bi2Sr2CaCu2O{8+x} in Angle Resolved Photoemission Spectroscopy (ARPES) experiments

摘要

We study the variation of the electronic properties at the surface of a hightemperature superconductor as a function of vacuum conditions in angle resolvedphotoemission spectroscopy (ARPES) experiments. Normally, under less than idealvacuum conditions the carrier concentration of Bi2Sr2CaCu2O{8+x} (Bi2212)increases with time due to the absorption of oxygen from CO2 and CO moleculesthat are prime contaminants present in ultra high vacuum (UHV) systems. We findthat in a high quality vacuum environment at low temperatures, the surface ofBi2212 is quite stable (the carrier concentration remains constant), however atelevated temperatures the carrier concentration decreases due to the loss ofoxygen atoms from the Bi-O layer. These two effects can be used to control thecarrier concentration in-situ. Our finding opens the possibility of studyingthe electronic properties of the cuprates as a function of doping across thephase diagram on the same piece of sample (i.e. with the same impurities anddefects). We envision that this method could be utilized in other surfacesensitive techniques such as scanning tunneling microscopy/spectroscopy.