Eur. Phys. J. Appl. Phys. (2015) 69: 10601 DOI: 10.1051/epjap/2014140185 THE EUROPEAN PHYSICAL JOURNAL APPLIED PHYSICS Regular Article Effects of hydrogen annealing and codoping (Mn, Fe, Ni, Ga, Y) of nanocrystalline Cu-doped ZnO dilute magnetic semiconductor Mohamed Bououdina 1,2, a and Aqeel Aziz Dakhel 1 1 Nanotechnology Centre, College of Science, University of Bahrain, P.O. Box 32038, Kingdom of Bahrain 2 Department of Physics, College of Science, University of Bahrain, P.O. Box 32038, Kingdom of Bahrain Received: 4 May 2014 / Received in final form: 19 November 2014 / Accepted: 2 December 2014 Published online: 7 January 2015 – c  EDP Sciences 2015 Abstract. Zinc oxide (ZnO) codoped with Cu and M ions (M = Mn, Fe, Ni, Ga, Y) powders were synthe- sised by simultaneous thermal co-decomposition of a mixture of zinc and metal complexes. The synthesised chemical formula for the prepared solid solution is Zn 0.97Cu0.01M0.02O. X-ray diffraction (XRD) analysis confirms the formation of single nanocrystalline structure of the as-prepared powders, thus, both Cu and M ions were incorporated into ZnO lattice forming solid solutions. Magnetic measurements reveal that all the as-synthesised doped ZnO powders gained partial (RT-FM) properties but with different strength and BH-behaviour depends on the nature of the doping (M). Furthermore, H 2 post-treatment was sub- sequently carried out and it was found that the observed RT-FM is enhanced. Very interestingly, in case of Ni dopant, the whole powder becomes completely ferromagnetic with coercivity (H c), remanence (Mr ) and saturation magnetisation (Ms ) of 133.6 Oe, 1.086 memu/g and 4.959 memu/g, respectively. The value of Ms was increased by ∼ 95% in comparison with as-prepared. 1 Introduction Dilute magnetic semiconductors (DMSs) oxides with partial replacement of cations by magnetic atoms are of great interest as magnetic components in spintronics [1, 2]. The practical applications of DMS in spintronics require that the DMS should exhibit ferromagnetism at and above room temperature. On other hand, the discovery of room-temperature ferromagnetism (RT-FM) in transition metal-doped transparent conducting oxides (TCOs) like ZnO or CdO broaden the possibility of application of DMS in modern technology. Wurtzite ZnO has an energy band-gap in the ultra- violet region (∼3.37 eV), resistivity (∼10 −2 Ω cm), and large exciton binding energy (60 meV) [3]. Films of ZnO could be made highly conductive with good optical trans- parency by appropriate doping. Therefore, ZnO has novel applications in optoelectronic devices such as lasers and solar cells, smart windows, as well as sensor devices for UV-visible photodetection and gas/liquid sensing [3]. The n-type electrical conduction properties of ZnO are caused by its natural intrinsic structural defects like oxy- gen vacancies (V O ) and zinc interstitials (Zn i ), that could be controlled and modified by doping with foreign metallic ions. On the other hand, doping can create stable exotic properties within ZnO, such as magnetic, a e-mail: mboudina@gmail.com mechanical, etc. that would diverse its field of applica- tions. This present work is focusing on tailoring the RT- FM properties of doped ZnO, aiming to use it in the field of dilute magnetic semiconductors (DMS). Of course, the strength of RT-FM depends on the quantity and quality of dopant metallic ions, that should be comparatively inves- tigated together with almost identical conditions of prepa- ration, that is the subject of the present work. In many previous research work, ZnO was studied doped with dif- ferent metallic ions, like Cu [4–6], Fe [7], Mn [8], Ni [9, 10], Ga [11] and Y [12]. It is important to note that among the large num- ber of research papers published so far in the literature, we have mentioned those references particularly, simply because they are directly related to the present work, from which the possible ion valences were used. In summary, DMS ZnO needs dopants from transition metals (TMs) like Fe, Mn, Ni, Co or rare earth ions, which create RT-FM. Moreover, the creation of stable RT-FM in doped ZnO needs also, an internal medium from itinerant charges as carrier for exchange magnetic interactions between localised spins of dopant ions. Indeed, more experimen- tal and theoretical research work are needed to explain the still challenging cause of RT-FM in DMS materials, although there are many previous papers reported in the literature dealing with that issue. It is important to note that RT-FM was also observed in un-doped oxides (d 0 FM) [13], which were known for a long time to be 10601-p1