Raman analysis of nitrogen doped ZnO

The mechanism of nitrogen doping is essential for making p-type ZnO. This paper demonstrates that Raman characterization is a potentially powerful tool to study the mechanism of nitrogen doping. We have observed new Raman features near 280, 510, 570, 642, 773, 1360 and 1565 cm− 1 shift in nitrogen doped ZnO (ZnO:N) thin films compared with undoped ZnO films. Peaks at 280, 510, 570, 642, and 773 cm− 1 are attributed to the nitrogen related defect complex. The Raman peaks at 1360 cm− 1 and 1565 cm− 1 shift are assigned to D—(disordered) and G—(Graphitic) bands associated with the carbon-related defect complex, respectively. The intensity and the intensity ratio of peaks at 1360 cm− 1 and 1565 cm− 1 have been found to be sensitive parameters that reflect the conductivity type of ZnO:N. Explanations are presented which correlate the Raman features to the electric conductivity of the films. From this analysis, we found that at temperature lower than or at 400 °C, nitrogen incorporation will form the nitrogen or possible nitrogen carbon related defect complex. As the growth temperature increases to 500 °C, the features associated with nitrogen are difficult to distinguish and the features associated to carbon begin to emerge. This observation possibly indicates the decrease of the nitrogen content and the increase of the carbon content in the ZnO:N film. The increase of carbon content may affect the donor behavior of the film. This observation suggests that growth conditions should be controlled to avoid carbon into the film.