Surface chemistry and surface electronic properties of ZnO single crystals and nanorods
(A) UPS spectra showing the VBM of treated single crystal ZnO surfaces. (B) Ionization potential values for treated ZnO single crystals comparing drying treatment vs UV-ozone. The ionization potential values are estimated to have an uncertainty of .
Zn binding energy values determined by XPS for treated ZnO (0001) and single crystals after treatment by UV-ozone or drying. The core level positions are estimated to have an uncertainty of .
Ionization potential values derived from UPS measurements for ZnO single crystals comparing the polar (0001) facet with the nonpolar facet after surface treatment. The ionization potential values are estimated to have an uncertainty of .
Ionization potential values as measured by UPS for treated (0001) and ZnO single crystals. The plot compares the as-received samples with those that had been annealed at in a ZnO box.
C core level spectra of contaminants on the surfaces of (A) (0001)-oriented single crystals of ZnO and (B) ZnO nanorods after surface treatment. The ionization potential values are estimated to have an uncertainty of .
Cl core level spectra of Cl residue on the surface of ZnO nanorods after drying and ozone pretreatments.
Zn core level spectra of ZnO nanorods after drying and UV-ozone pretreatments. The ozone-treated peak is shifted to lower binding energy by , which is attributed to an increase in upward band bending.
VBM spectra of ZnO nanorods after drying and UV-ozone pretreatments. The shoulder on the VBM edge of the ozone-treated spectra between 3 and is attributed to the possible emission from surface states.
Surface electronic properties of ZnO nanorods as measured by UPS after treatment by drying and UV-ozone in A and B, respectively. The EA, IP, and work function are notated.
HBEC measured from treated ZnO single crystals before and after deposition of a thin layer of P3HT. The shift in HBEC is indicative of the formation of an interface dipole of the same magnitude. The ionization potential values are estimated to have an uncertainty of .
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