IOP PUBLISHING JOURNAL OF PHYSICS D: APPLIED PHYSICS J. Phys. D: Appl. Phys. 42 (2009) 035001 (4pp) doi:10.1088/0022-3727/42/3/035001 Influence of the substrate temperature on the electrical and magnetic properties of ZnO : N thin films grown by pulse laser deposition Chang-Feng Yu 1 , Sy-Hann Chen 1 , Shih-Jye Sun 2 and Hsiung Chou 3 1 Department of Applied Physics, National Chiayi University, Chiayi 60004, Taiwan 2 Department of Applied Physics, National University of Kaohsiung, Kaohsiung 811, Taiwan 3 Department of Physics and Center for Nanoscience and Nanotechnology, National Sun Yat-Sen University, Kaohsiung 804, Taiwan E-mail: cfyu@mail.ncyu.edu.tw Received 15 August 2008, in final form 19 November 2008 Published 18 December 2008 Online at stacks.iop.org/JPhysD/42/035001 Abstract We investigated the effect of the substrate temperature on the magnetic, electrical and optical properties of nitrogen-doped ZnO thin films. Experiments showed that a high substrate temperature depresses the deposition rate and produces much thinner films displaying more robust ferromagnetism. In addition, the resistivity decreased as the substrate temperature increased and all of the nitrogen-doped films, at different substrate temperatures, had larger gaps than the pure ZnO film. 1. Introduction Magnetic ion doped ZnO thin films [1, 2] have attracted the interest of many researchers because of their room temperature ferromagnetism [3, 4]. This large band gap transparent material [5, 6] also has extremely high potential in industrial applications [7]. Interestingly, non-magnetic ion doped ZnO thin films also reveal robust ferromagnetism, e.g. nitrogen- doped ZnO thin films (ZnO : N) [8, 9]. The mechanism behind the enhancement of ferromagnetism by the doped nitrogen is still unclear. Because of the completely filled d-orbits of the non-magnetic ion doped ZnO thin films, the origin of the ferromagnetism is out of the ordinary. Some researchers believe that the magnetic mechanism of non-magnetic ion doped thin films of transition metal oxide comes from the localized states of oxygen defects [10–12], which is different from the bound magnetic polaron (BMP) mechanism proposed by Coey [3] for magnetic ion doped transition metal oxides. Undoped zinc oxide films generally exhibit natural n-type conduction due to the presence of intrinsic donor-type defects induced by deviation from stoichiometry. Therefore, one of the major obstacles in the development of ZnO material is the difficulty encountered in finding an efficient p-type dopant. Theoretical calculation predicts that nitrogen is an outstanding candidate in current research for p-type doping of ZnO. A number of groups have been trying to realize p-type ZnO employing nitrogen as a dopant source by various methods [13, 14]. Despite the many reports on the successful growth of p-type ZnO films by nitrogen doping, there were also a number of reports in which the groups were not able to reproduce and maintain the same results. Unfortunately, this p-type doping is unstable [15], but reveals the particular doping level of nitrogen in ZnO. In fact, some contradictory results represented in ZnO films by nitrogen doping have revealed n-type electricity [16, 17]. The nature of conduction (n- or p-type) for ZnO : N seems to depend on the fabrication process and conditions. We think that the substrate temperature is an important parameter in ZnO : N thin film deposition. We utilized pulsed laser deposition (PLD) under a mixed atmosphere of O 2 or N 2 O to deposit ZnO : N thin films on glass substrates at different substrate temperatures. Our results showed that the magnetic, electrical and optical properties of the ZnO : N thin films were dependent on the substrate temperature during the film deposition. Although the parameters of the material’s properties are entangled and complicated, through an investigation of our results, we propose some mechanisms for determining them. 0022-3727/09/035001+04$30.00 1 © 2009 IOP Publishing Ltd Printed in the UK