Charge exchange between low energy alkali ions and cerium oxide surfaces

Adsorption of iodine and potassium onBi2Sr2CaCu2O8+δGann1, Cao2, Wu3 et al. 2010Phys. Rev. B10190View full textAdd to dashboardCite

“…Consequently, the result for BSCCO should be qualitatively the same as on the ceria surface, but less pronounced, and that is indeed what is seen. In CeO 2 , the neutralization probability changed from 100% down to about 40% as the trajectories became more grazing, 19 whereas here the change is more modest, from perhaps 70% to 40%. Figure 3 shows the effects that alkali ͑K͒ and a halogen ͑I͒ adatoms have on the neutralization of Na + ions scattered There is at most a marginal dependence on incident energy, with a downward trend as emission angle is increased ͑corresponding with a lower perpendicular velocity͒.…”

“…19 At electropositive sites on a surface, the local work function would be reduced, pushing the Fermi energy up relative to the ionization level and leading to increased neutralization of scattered alkaliions. Conversely, at electronegative sites the work function is increased, pushing the Fermi energy down and leading to a decrease in neutralization.…”

Internal Polarization of Oxygen Adatoms on Polycrystalline Ta Investigated by Na-Ion Scattering

“…Normally, smaller work functions lead to a larger NF, and vice versa. For systems with an inhomogeneous LEP, such as in the presence of polar adatoms [8,13] or at the surface of metal oxides [14], it is the potential at a particular point close (1 A) to the scattering site, rather than the global work function, that determines the NF.…”

“…Tantalum foil (ESPI, purity 3N8) was loaded onto an XYZ rotary manipulator in an ultrahigh vacuum chamber (base pressure 2 10 ÿ10 Torr) described previously [14]. The clean surface was prepared by 500 eV Ar sputtering at a beam density of 1:0 A=cm 2 for 1 h. Ta foil was (partially) oxidized by annealing at 500 C in 2 10 ÿ7 Torr oxygen for 10 min.…”

“…The STM measurements were carried out at constant current mode (1 nA) with the sample biased at ÿ0:5 V so that filled states were imaged. The TOF setup, and the methods used to collect spectra and calculate the NF, were described previously [14]. Figure 1 shows TOF spectra collected for the scattering of 3.0 keV 23 Na from clean and partially oxidized Ta surfaces.…”