Electronic structure variations of polar and nonpolar ZnO lattices with nitro­gen-ion bombardment using synchrotron-based in situ photoemission and X-ray absorption spectroscopy

Surface polarity with different crystal orientations has been demonstrated as a crucial parameter in determining the physical properties and device applications in many transition metal oxide and semiconductor compound systems. The influences of surface polarity on electronic structures in nitro­gen-incorporated ZnO lattices have been investigated in the present work. The successful doping of nitro­gen atoms in ZnO lattices is suggested by the existence of N-related chemical bonds obtained from X-ray photoelectron spectroscopy analysis where a pronounced N–Zn peak intensity has been observed in the ()-terminated polar ZnO compound compared with the ()-terminated nonpolar ZnO compound. An energy shift of the valence band maximum towards the Fermi level has been resolved for both polar and nonpolar ZnO lattices, whereas a charge redistribution of the O 2p hybridized states is only resolved for o-plane ZnO with a polar surface. Angular-dependent X-ray absorption analyses at the O K-edge reveal enhanced surface-state contributions and asymmetric O 2p orbital occupations in the ()-terminated o-plane ZnO compound. The results shed light on the efficient nitro­gen doping in ZnO lattices with polar surfaces. The comprehensive electronic structure investigations of correlations between impurity doping and surface polarity in ZnO lattices may also offer guidance for the material design in other transition metal oxide and semiconductor systems.