Structural and luminescence properties of SrAl 2 O 4 :Eu 2 þ ,Dy 3 þ ,Nd 3 þ phosphor thin films grown by pulsed laser deposition A.H. Wako a,n , F.B. Dejene a , H.C. Swart b a Department of Physics, University of the Free State, QwaQwa Campus, Private Bag X13, Phuthaditjhaba 9866, South Africa b Department of Physics, University of the Free State, P.O. Box 339, Bloemfontein ZA-9300, South Africa article info Article history: Received 7 May 2015 Received in revised form 22 September 2015 Accepted 27 September 2015 Available online 30 September 2015 Keywords: Solution-combustion SrAl 2 O 4 :Eu 2 þ ,Dy 3 þ ,Nd 3 þ Thin films Sr/Al mol% Argon Photoluminescence abstract Thin films of Eu 2 þ doped and Dy 3 þ ,Nd 3 þ co-doped Strontium Aluminate (SrAl 2 O 4 :Eu 2 þ ,Dy 3 þ ,Nd 3 þ ) phosphors were grown on Si(100) substrates by a pulsed laser deposition (PLD) technique using a 266 nm Nd:YAG pulsed laser under varying substrate temperature and the working atmosphere during the film deposition process. The effect of substrate temperatures and argon partial pressure on the structure and luminescence properties of the as-deposited SrAl 2 O 4 :Eu 2 þ ,Dy 3 þ ,Nd 3 þ phosphor thin films were analysed. XRD patterns showed that with increasing substrate temperature and argon partial pressure the peaks in the direction (220) shifted to the lower 2-theta angles. Photoluminescence (PL) data collected in air at room temperature revealed a slight shift in the peak wavelength of the PL spectra observed from the thin films when compared to the PL spectra of the phosphor in powder form, which is probably due to a change in the crystal field. The PL intensity of the samples was highest for 100 °C substrate temperature and 20 mTorr argon partial pressure. Due to this, the effect of argon partial pressure was studied at a constant substrate temperature of 100 °C while the effect of Substrate tem- peratures recorded at 20 mTorr argon pressure respectively. & 2015 Elsevier B.V. All rights reserved. 1. Introduction Long afterglow or persistent phosphors have the ability of ab- sorbing energy from UV or sunlight and then release it slowly in the dark [1,2]. Inorganic phosphors doped with rare earth ele- ments show broad band emission from blue to red which makes them suitable for a variety of industrial applications, such as lu- minescent pigments, fluorescent lamps, color display, plasma display panels (PDP), radiation dosimetry and X-ray imaging [3]. The type and duration of emission from a phosphor is affected by a number of parameters such as the type and amount of activators or dopants, the structure of the host lattice, the method of pre- paration or growth conditions and other post-treatments. These parameters play a significant role in inducing a crystal field effect within the host matrix which in turn influences the emission wavelength, its intensity and lifetime. The main task would therefore be to optimize these factors so at to obtain a phosphor that gives the best performance for the desired application. Luminescent Eu 2 þ -doped strontium aluminate (SrAl 2 O 4 :Eu 2 þ ) phosphors have been studied extensively because they exhibit excellent properties such as bright and long-persistent phosphorescence which glow for many hours and are also safer and chemically stable and free from radioactive radiations as compared with sulfide phosphors like ZnS:Cu [4]. Persistent lu- minescence and intensity can be enhanced by co-doping SrAl 2 O 4 :Eu 2 þ with other rare earth elements [5]. Most of the re- search mainly focused on the trivalent dysprosium (Dy 3 þ ) and not Neodymium (Nd 3 þ ) ions as co-dopants. SrAl 2 O 4 :Eu 2 þ ,Dy 3 þ ,Nd 3 þ phosphor powder can be synthesized using methods such as co- precipitation [6], solid state reaction [2] and sol–gel [7]. As com- pared with these conventional methods, solution-combustion synthesis technique [3–5] used in this work to prepare SrAl 2 O 4 :Eu 2 þ ,Dy 3 þ ,Nd 3 þ phosphor powders is facile, energy saving, safe and fast [8]. Most of the previous studies on SrAl 2 O 4 :Eu 2 þ were carried out on the phosphor powder and there are few reports on thin films more so those made using the PLD technique [9]. In this paper we report the structural and luminescence properties of as–prepared SrAl 2 O 4 :Eu 2 þ ,Dy 3 þ ,Nd 3 þ phosphor powder and thin films. Thin film phosphors have several advantages over powders in that they exhibit better thermal stability, better adhesion to the substrate, higher lateral resolution and less out gassing in device applications [10]. Several methods have been used to grow thin films such as Chemical Bath Deposition (CBD) [11], rf magnetron sputtering [12], pulsed laser deposition (PLD) [13] and epoxide-catalyzed sol–gel methods [14]. However PLD has several advantages over other Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/physb Physica B http://dx.doi.org/10.1016/j.physb.2015.09.049 0921-4526/& 2015 Elsevier B.V. All rights reserved. n Corresponding author. E-mail address: wakoah@ufs.ac.za (A.H. Wako). Physica B 480 (2016) 116–124