Journal of Applied Research and Technology ISSN: 1665-6423 [email protected] Centro de Ciencias Aplicadas y Desarrollo Tecnológico México Parveen, Bushra; ul-Hassan, Mahmood; Khalid, Zeeshan; Riaz, Saira; Naseem, Shahzad Room-temperature ferromagnetism in Ni-doped TiO2 diluted magnetic semiconductor thin films Journal of Applied Research and Technology, vol. 15, núm. 2, 2017, pp. 132-139 Centro de Ciencias Aplicadas y Desarrollo Tecnológico Distrito Federal, México Available in: http://www.redalyc.org/articulo.oa?id=47450569005 How to cite Complete issue Scientific Information System More information about this article Network of Scientific Journals from Latin America, the Caribbean, Spain and Portugal Journal's homepage in redalyc.org Non-profit academic project, developed under the open access initiative Available online at www.sciencedirect.com Journal of Applied Research and Technology Journal of Applied Research and Technology 15 (2017) 132–139 www.jart.ccadet.unam.mx Original Room-temperature ferromagnetism in Ni-doped TiO2 diluted magnetic semiconductor thin films a,b a,∗ a c c Bushra Parveen , Mahmood-ul-Hassan , Zeeshan Khalid , Saira Riaz , Shahzad Naseem a Materials Growth and Simulation Laboratory, Department of Physics, University of the Punjab, Lahore 54590, Pakistan b Department of Physics, Lahore Garrison University, Lahore 54590, Pakistan c Centre of Excellence in Solid State Physics, University of the Punjab, Lahore 54590, Pakistan Received 20 September 2016; accepted 20 January 2017 Available online 31 March 2017 Abstract We report undoped and Ni-doped TiO2 (xNi = 0.00, 0.50, 1.00, 1.50, 2.00 and 2.50 wt.%) thin films fabricated on glass substrates by using a combination of solid-state reaction and dip coating techniques. The structural properties are observed by X-ray diffraction (XRD), which have ◦ depicted that annealing at 650 C results in rutile Ni-doped TiO2 as a major phase along with a minor anatase phase. The surface morphology of the deposited thin films, as measured by scanning electron microscopy (SEM), indicates granular spherical shaped nanostructures. Room-temperature ferromagnetism (RTFM) has been illustrated by all the grown thin films, as elucidated by vibrating sample magnetometer (VSM). Although Ni content has no pronounced effect on the crystallinity that indicates a substitutional replacement of Ni in TiO2 lattice, however, Ni content is observed to influence the ferromagnetic behavior. Therefore, the present study signifies the potential spintronic applications of Ni-doped TiO2 diluted magnetic semiconductors, fabricated by a low-cost method, as it exhibits RTFM with nanograins at the surface. © 2017 Universidad Nacional Autónoma de México, Centro de Ciencias Aplicadas y Desarrollo Tecnológico. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Keywords: Diluted magnetic semiconductors; Dip coating; Solid-state reaction; Room-temperature ferromagnetism (RTFM); Vibrating sample magnetometer 1. Introduction Sikora, Gaworska-Koniarek, & Iwan, 2015; Paulauskas et al., 2013). TiO2 doped with various magnetic ions for achieving In the last few years, thin film technology has been playing room-temperature ferromagnetism (RTFM) is one of the attrac- a vital role in the fabrication of solid-state magnetic storage tive aspects in spintronics research. Basically, TiO2 appears in devices to study and realize novel phenomena to meet the three different crystallographic phases namely, anatase, rutile requirements of the integrated-circuit industry. The cost of fab- and brookite. Among which rutile phase is the preferred one. rication of thin films is very low as compared to that of their bulk Rutile phase has been widely studied, as it is non toxic with high counterparts. Moreover, the charge transport and the informa- transparency in the visible region, it has high refractive index, tion storage can effectively be realized in nanoscale devices by high dielectric constant and good chemical stability (Oganisian employing thin films. Diluted magnetic semiconductors have a et al., 2015; Paulauskas et al., 2013; Sahdan, Nayan, Dahlan, prominent place in traditional semiconductor-based spintronic Mahmoud, & Hashim, 2012); therefore, it is considered as one research. Traditional semiconductors, doped with a small con- of the suitable photocatalysts in heterojunctions. Also, it has centration of magnetic ions to associate magnetic degree of potential applications including gas sensors, membranes, LEDs, freedom, have become suitable for both current controlling fibers, light transparent electrodes, heat reflectors and optical and magnetic storage device applications (Oganisian, Hreniak, gain media (Akpan & Hameed, 2010; Chen, Yang, Wang, & Jiang, 2006). There are many reports in the literature, which indicates that the band gap of TiO can be tapered by doping ∗ 2 Corresponding author. with transition metals (Fe, Cr, Mn, Ni), nonmetals (F, I, P, N, E-mail address: [email protected] ( Mahmood-ul-Hassan). S), rare earth elements (La, Gd, Nd, Er, Pr) and alkaline earth Peer Review under the responsibility of Universidad Nacional Autónoma de México. metals (Be, Mg) etc., that enhance the photocatalytic activity in http://dx.doi.org/10.1016/j.jart.2017.01.009 1665-6423/© 2017 Universidad Nacional Autónoma de México, Centro de Ciencias Aplicadas y Desarrollo Tecnológico. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). B. Parveen et al. / Journal of Applied Research and Technology 15 (2017) 132–139 133 the visible light (Ahmad et al., 2010; Al-Jawad, 2014; Asahi, 2012; Kuppan et al., 2016a, 2016b; Xu et al., 2009). As it is Morikawa, Irie, & Ohwaki, 2014; Ayieko, Musembi, Waita, evident in the literature, no report exist on Ni-doped TiO2 for Aduda, & Jain, 2013; Buzby et al., 2006; Di Valentin, Pacchioni, spintronics applications as DMS, fabricated by low cost method, & Selloni, 2005; Gültekin, 2014; Hamal & Klabunde, 2007; to exhibit ferromagnetism at room temperature (RT). Hermawan, Pranowo, & Kartini, 2011; Hernández-Martínez, In this work, Ni-doped TiO2 thin films are deposited by Estevez, Vargas, Quintanilla, & Rodríguez, 2012; Li, Ding, employing a combination of solid-state reaction and dip coating Liu, & Ning, 2013; Niemela, Yamauchi, & Karppinen, 2014; techniques with a focus on magnetic device applications, with Seery, George, Floris, & Pillai, 2007; Sobana, Muruganadham, various dopant concentrations (xNi = 0.00, 1.00, 1.50, 2.00 and & Swaminathan, 2006; Tian, Gao, Deng, et al., 2013; Tian, Gao, 2.50 wt.%). Ni is a suitable transition metal magnetic dopant Kong, et al., 2013; Yang et al., 2007), which indicates poten- for TiO2 and this diluted magnetic semiconductor has worth tial opto-electronic device applications. A surprising fact is the applications in magnetic data storage devices. The structural, presence of room-temperature ferromagnetism in undoped TiO2 morphological and ferromagnetic properties have been explored (Hong, Sakai, Poirot, & Brizé, 2006; Yoon et al., 2006). The using XRD, SEM and VSM, respectively. The results obtained ferromagnetism is reported to be originated because of oxy- are correlated and compared with the literature and significant gen vacancies acting as n-type dopant and cause a magnetic points have been elaborated with a focus on the utilization of the order. Through theoretical calculation (Paxton & Thien-Nga, studied thin films for data storage applications. 1998) the magnetic ordering has been demonstrated to be orig- inated because of the Ti states operating within the bandgap. 2. Experimental procedures Transition metal elements are preferred as dopants because of their almost similar ionic radii with the Ti-cations in the host In this study, we have employed a very simple and low cost TiO2 lattice, and additionally mediate ferromagnetism. Among method to prepare Ni-doped (xNi = 0.00, 0.50, 1.00, 1.50, 2.00 +2 many transition metal ion dopants, Ni is considered to be more and 2.50 at wt.%) TiO2 Thin films on glass substrate. For the efficient dopant in TiO2, as it can improve electrical and mag- fabrication of undoped thin film, 3.2 g Titanium dioxide powder netic properties (Ayieko et al., 2013; Li et al., 2013; Nosaka, was added into ethanol solution and stirred using a magnetic ◦ Matsushita, Nishino, & Nosaka, 2005). Oganisian et al., synthe- stirrer for 1 h at 70 C, to achieve a well-mixed and uniform sized Fe-doped TiO2 by sol–gel method and studied the effect of solution. The TiO2 thin film was fabricated onto a glass sub- doping concentration on the magnetism, and suggested the for- strate using dip coating. In this method ultrasonically cleaned mation of multi-domain structure that enhances with Fe contents glass substrate were dipped into the prepared solution for 2–3 (Oganisian et al., 2015). Choudhary et al., have reported the times to get a suitable and uniform thickness of the film. The role of Oxygen defects in assisting paramagnetic to ferromag- TiO2 thin film deposited on the glass substrate was dried in an ◦ netic phase change activated through the Fe doping in TiO2 electric oven at 150 C for 15 min. In this way one layer of TiO2 (Choudhury, Verma, & Choudhury, 2014). Similarly, Ni-doped was deposited on the glass substrate. This process was repeated TiO2 is employed to study the effect of dopants on the ferromag- 3 times to get appropriate TiO2 layer thickness. Similarly, Ni- netic properties of TiO2 stabilized in rutile phase (Park, Choi, doped (xNi = 0.50, 1.00, 1.50, 2.00 and 2.50 at wt.%) TiO2 thin Lee, Kim, & Kim, 2007). On the other hand, J. Tian et al. fab- films were fabricated by adding appropriate amounts of NiO ricated TiO2 thin films by sol–gel process and observed that powders (according to their molar masses) into the TiO2 solu- increase in transition metal concentration reduces magnetization tion. All the prepared thin films have been annealed in a digital ◦ (Tian, Gao, Deng, et al., 2013; Tian, Gao, Kong, et al., 2013). furnace at 650 C for 60 min, to enhance the crystallinity.