Identification of nitrogen chemical states in N-doped ZnO via x-ray photoelectron spectroscopy

Abstract

Nitrogen-doped films of ZnO grown by two methods, metalorganic chemical vapor deposition (MOCVD) and reactive sputtering, were studied with x-ray and ultraviolet photoelectron spectroscopy (XPS and UPS). Systematic differences in the N chemical states were observed between films grown by sputtering and MOCVD: only two N chemical states were observed in films grown by reactive sputtering, whereas four N chemical states were observed in MOCVD films. To aid in the assignment of the N chemical states, photoemission data from the polycrystalline films were compared with data taken on N2+-implanted Zn metal and N2+-implanted ZnO. High-resolution core level spectra of the N1s region indicated that nitrogen can occupy at least four different chemical environments in ZnO; these include the NO acceptor, the double donor (N2)O, and two carbon–nitrogen species. Valence band spectra indicate that the Fermi energy of all films studied was near the conduction band minimum, implying that the films remained n-type after nitrogen doping. Analysis of the relative amounts of acceptors and donors identified by XPS in the sputter-grown films provides clues as to why only a small percentage of incorporated nitrogen is found to contribute to carriers, and points toward possible paths to higher quality ZnO:N films.

Effect of substrate temperature on the photoelectrochemical responses of Ga and N co-doped ZnO films

“…Furthermore, the Ga 2 O 3 source provides more oxygen during the sputtering process [11], leading to decreased oxygen vacancies and enhanced crystallinity. A similar effect of the Ga oxide source on ZnO crystallinity has also been reported by other groups [26]. The crystallite size of Ga-N co-doped ZnO films deposited at a substrate temperature of 300 and 500°C is 35 and 24 nm, respectively, indicating that more N is incorporated in these films.…”

“…Argon ion sputtering (3 keV, 0.8 lAmm -2 , 120 s) was used to clean samples prior to analysis. Other aspects of the photoemission system are described in detail elsewhere [26].…”

Effective Suppression of Surface Recombination in ZnO Nanorods Arrays during the Growth Process

“…From Fig.8, we can see that one peak located at 400.02 ±0.3 eV can be observed in both samples. It is known that the N 1s peak from molecularly adsorbed NH 3 on metal and semiconductor surfaces appears at 400-401 eV, whereas for the partially decomposed species, i.e., NH x (x= 1, 2), N 1s peak appears at 398-399.4 eV [52][53][54]. Thus, the peak at 400.02…”

Influence of anneal atmosphere on ZnO-nanorod photoluminescent and morphological properties with self-powered photodetector performance

“…[18][19][20] However, studies have since shown that N-doping compensates p-type behaviour by forming shallow donors rather than acceptors, consequently p-type ZnO is unlikely to form. [21][22][23][24][25] Point defects situated deep in the ZnO bandgap (E g ) give rise to photoluminescence (PL) referred to as deep-level emission (DLE) observed under excitation >E g . This DLE emission has been employed in visible light-emitting diodes 26,27 and photodetectors.…”