Journal of Alloys and Compounds 527 (2012) 1–4 Contents lists available at SciVerse ScienceDirect Journal of Alloys and Compounds jou rn al h om epage: www.elsevier.com/locate/jallcom Letter Blue shift in band gap and photoluminescence of pulsed laser deposited SrS:Ce/quartz thin ﬁlm nanophosphors Ankush Vij a,b , Sanjeev Gautam a,b , Ravi Kumar e , Amit K. Chawla c , Ramesh Chandra d , Nafa Singh f , Keun Hwa Chae a,∗ a Advanced Analysis Center, Korea Institute of Science and Technology, Seoul 136-791, Republic of Korea b Pohang Light Source, San31 Hyojadong, Namgu, Pohang 790-784, Republic of Korea c College of Engineering Studies, University of Petroleum and Energy Studies, Dehradun 248-007, India d Institute Instrumentation Centre, Indian Institute of Technology, Roorkee 247-666, India e Centre for Material Science and Engineering, National Institute of Technology, Hamirpur 177-005, India f Department of Physics, Kurukshetra University Kurukshetra, Kurukshetra 136-119, India a r t i c l e i n f o Article history: Received 12 October 2011 Received in revised form 7 February 2012 Accepted 8 February 2012 Available online xxx Keywords: SrS:Ce Thin ﬁlm nanophosphors PLD Photoluminescence a b s t r a c t We report on the synthesis of single phase SrS:Ce/quartz thin ﬁlm nanophosphors at a substrate tempera- ture of 400 ◦ C using pulsed laser deposition. The AFM and FESEM micrographs reveal the island structure with granular growth of nanophosphors. The average crystallite size (∼ 13 nm using Williamson–Hall plot), the average grain size (∼ 40 nm using AFM) and the blue shift in band gap conﬁrm the nanostruc- ture formation. Interestingly, the photoluminescence emission corresponding to 5d-4f transitions in Ce 3+ ion under the cubic crystal ﬁeld of SrS also exhibits a signiﬁcant blue shift, which can be explained using phenomenological crystal ﬁeld model modiﬁed by covalency factor. © 2012 Elsevier B.V. All rights reserved. 1. Introduction Rare earth ions doped alkaline earth sulﬁde (AES) phosphors are potential candidates for luminescent applications such as optical storage media, electroluminescent displays, radiation dosimetry, infrared sensors, ionoluminescence, etc. due to their high lumines- cence yields [1–5]. SrS, a member of AES family, acts as a good insulator due to indirect band gap of 4.2 eV in the bulk form. How- ever, SrS doped with suitable activators such as rare earth ions exhibits excellent luminescent properties [6,7]. In addition, these phosphors emit visible light without self absorption. Generally, thin ﬁlm phosphors offer several advantages over the conventional powder phosphor screens, including high resolution, thermal stability, uniformity, density, and possibly a much lower susceptibility to charging [8]. There are several reports available on the synthesis of SrS based thin ﬁlms on different substrates using pulsed laser deposition (PLD) [8,9], e-beam evaporation [10], RF sputtering [11], atomic layer epitaxy [12], etc. Since in low dimensional systems, electrons and holes are spatially conﬁned causing quantum conﬁnement effects, energy levels and hence ∗ Corresponding author. Tel.: +82 542791192; fax: +82 542791599. E-mail address: khchae@kist.re.kr (K.H. Chae). optical properties become considerably different from their bulk counterparts [13–15]. This has generated a considerable interest in exploring nanomaterials both in powder [16–18] and thin ﬁlm form [19–21]. Recently SrS based nanophosphors have been investigated in detail but only in their powder form [7,22,23]. In this letter, we discuss the hitherto unreported synthesis and characterization of SrS:Ce thin ﬁlm nanophosphors. The effect of different substrate temperatures and subsequent in situ post deposition annealing on the structure of thin ﬁlm nanophosphors has been investigated. 2. Experimental details SrS:Ce thin ﬁlm nanophosphors were deposited on quartz sub- strates using PLD. Prior to ﬁlm deposition, substrates were properly cleaned in an ultrasonicator using methanol and deionized water. The source material Ce (0.5 mol%) doped SrS powder for PLD was synthesized by solid state diffusion method in the presence of thio- sulfate as a ﬂux [7]. The synthesized powder was hydraulically pressed into the pellet form and sintered at 1000 ◦ C for 4 h in Ar atmosphere to prevent oxidation. The sintered pellet was used as the target to deposit thin ﬁlms by using a PLD chamber (Excel instruments, Mumbai) and a KrF excimer laser (Lambda Physik,  = 248 nm). The distance from target to substrate was ﬁxed at 3 cm and the laser energy was adjusted at 250 mJ. The deposition was 0925-8388/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.jallcom.2012.02.063