N-doped zinc oxide (ZnO) thin films grown on c-face sapphire (c-Al

2

O

3

) substrate by plasma-assisted molecular beam epitaxy (P-MBE) in Zn-rich condition were reported. NO gas activated by a radio frequency source was used as both oxygen and nitrogen sources. The crystalline structure

chemical composition and electrical properties were investigated by X-ray diffraction (XRD) spectra

X-ray photoemission spectra (XPS) and temperature-dependent Hall effect measurement. In XRD spectra

the full width at half maximal (FWHM) of (0002) diffraction peak for N-doped ZnO was broader than that of undoped sample due to the incorporation of nitrogen atoms in the N-doped ZnO film. At the same time

X-ray photoelectron spectra (XPS) showed the atomic fractions for N

Zn and O are 1.1%

53.7% and 45.2%

respectively. XPS results proved nitrogen atoms had occupied the oxygen lattice and acted as acceptors. It also proved that ZnO was grown in a Zn-rich condition in the experiment. However

the Hall effect measurement (at room temperature) showed the sample was still n-type conduction with a higher carrier concentration (2.15×10

20

cm

-3

). This concentration was much higher than that of undoped sample (10

18

cm

-3

). In order to further investigate the electrical property of ZnO

the sample was annealed in O

2

ambient at 500℃ for 30 min. The temperature dependent of Hall effect measurements showed different behaviors between the as-grown and the annealed samples. Before annealing

the as-grown sample showed metal conduction behavior

while it showed normal semiconductor conduction behavior after annealing. According to theory analysis and calculation

it was believed after compensating the limited acceptor(nitrogen atoms occupied the oxygen lattice)

the behavior for residual ZnO atoms is similar to heavy-doped conduction in ZnO sample and caused the ZnO sample changed from semiconductor conduction to metal condution behavior (Mott transition).