Characterization of nitrogen doped p-type ZnO thin films prepared by reactive ion beam sputter deposition

Nitrogen doped ZnO (ZnO:N) thin films have been successfully prepared by reactive ion beam sputter deposition. The ZnO:N thin films show a preferred growth orientation along the (002) direction regardless of nitrogen flow rates. Raman spectroscopy analysis shows nitrogen related local vibration modes at 275 and 576 cm(-1) in addition to the ZnO E-2 (high) mode at 436 cm(-1), indicating a successful incorporation of nitrogen into the ZnO. Both of the peak intensities of 275 and 576 cm(-1) reach a maximum after post-growth annealing at 500 degrees C. ZnO:N deposited with a 0.5 sccm nitrogen flow rate exhibits p-type conductivity with a hole concentration of 2.1 x 10(17)/cm(3) and a mobility of 3 cm(2)V(-1) s(-1) after annealing at 500 degrees C. Conversion to p-type conductivity was not observed on ZnO:N deposited with higher nitrogen flow rates. The p-type conductivity remains stable after it was stored at ambient conditions for more than two months. The p-type ZnO:N thin film is transparent in the visible range with a transmittance larger than 83%. SIMS analysis indicates that nitrogen concentration of less than 1.2 at.% results in the successful preparation of p-type ZnO:N. ZnO:N deposited with higher nitrogen concentration results in n-type conductivity which is likely due to the formation of molecular nitrogen replacing oxygen sites that act as double donors (N-2)(o). (C) 2012 Elsevier B.V. All rights reserved.