AVS 51st International Symposium
    Semiconductors Tuesday Sessions
       Session SC-TuP

Paper SC-TuP8
XPS and UPS Study of ZnO:N Thin Films

Tuesday, November 16, 2004, 4:00 pm, Room Exhibit Hall B

Session: Poster Session
Presenter: C.L. Perkins, National Renewable Energy Laboratory
Authors: C.L. Perkins, National Renewable Energy Laboratory
X. Li, University of Texas at Arlington
S. Asher, National Renewable Energy Laboratory
T.J. Coutts, National Renewable Energy Laboratory
S.-H. Lee, National Renewable Energy Laboratory
Correspondent: Click to Email
There are strong motivations for obtaining nitrogen-doped p-type ZnO, including the possibilities of air-stable, high quality UV lasers, detectors, and efficient photocatalytic water splitting. Problems remain with the growth of this material however. Reproducibility of conductivity type is difficult, and the distributions and identities of nitrogen species in N-containing ZnO films are not well known. Although theory predicts that N can be incorporated in at least two different states, one of which, N@sub 2@ occupying a position on the oxygen sublattice (N@sub 2O@) should be a double shallow donor, and the other, NO, being the desired acceptor, there have been few determinations of the chemical states of nitrogen in ZnO:N materials. In order to gain a better understanding of their chemical and electronic properties, we have examined via XPS and UPS thin films of ZnO:N produced by two different methods. MOCVD films were grown using diethylzinc and nitric oxide. Sputtered films were produced with a Zn target and a mixture of O@sub 2@ and N@sub 2@. Core level photoemission shows that the films contain 0.5-2.5 % nitrogen, and that the nitrogen occupies at least four different chemical environments. With UPS the relative positions of the films' valence bands are determined with respect to the Fermi level. Results from the thin polycrystalline films are compared to initial results obtained on ZnO(0001) single crystals reacted in UHV with nitric oxide, and with data obtained from N-implanted Zn foil. Definitive XPS peak assignments are made for N@sub 2O@, N@sub O@, and two other nitrogen chemical states that have not previously been identified in ZnO:N.