Improved luminescence properties of pulsed laser deposited Y 3 (Al,Ga) 5 O 12 :Tb thin films by post deposition annealing A. Yousif a,b , H.C. Swart a,n , O.M. Ntwaeaborwa a a Physics Department, University of the Free State, P.O. Box 339, Bloemfontein ZA 9300, South Africa b Physics Department, Faculty of Education, University of Khartoum, P.O. Box 321, 11115 Omdurman, Sudan article info Article history: Received 21 November 2012 Accepted 19 April 2013 Available online 9 May 2013 Keywords: PLD Y 3 (Al,Ga) 5 O 12 :Tb Thin films Annealing effect Photoluminescence (PL) Cathodoluminescence (CL) abstract Y 3 (Al,Ga) 5 O 12 :Tb thin films were successfully deposited on Si (1 0 0) substrates in an oxygen working atmosphere by the pulsed laser deposition (PLD) technique. The as-deposited films were amorphous but crystallized when annealed in air at 400 1C and 800 1C for 1 h as confirmed by X-ray diffraction. Three dimensional atomic force microscopy (AFM) images of the as-deposited film show well defined spherically grains that were uniformly distributed over the surface with a root mean square (RMS) roughness value of 9 nm. After annealing at 800 1C the surface became smooth and the RMS value was reduced to 6 nm. The smooth layer was confirmed to be a surface oxide layer enriched with Ga from the images captured using a nano-scanning Auger electron microprobe (NanoSAM). The PL intensities were observed to increase as a function of annealing temperatures and this was attributed to improvement of the crystallinity of the films and a possible variation of Ga concentration in the thin films. In addition, cathodoluminescence (CL) properties of the films were recorded when the films were irradiated with a beam of electrons in the vacuum chamber of the Auger electron spectrometer. The CL intensity of the deposited film was recorded as a function of electron dose as well as the accelerating voltage. & 2013 Elsevier B.V. All rights reserved. 1. Introduction Luminescent films play an important role in high resolution display devices such as cathode-ray tubes (CRTs), electrolumines- cent devices, plasma display panels, and field emission displays (FED's). Displays based on thin film phosphors are characterized by high contrast and resolution, good thermal conductivity as well as a high degree of uniformity and better adhesion [1–3]. Most phosphor materials consist of multi-components and their lumi- nescence efficiency is largely affected by the right stoichiometry and growth mode. One of the most important things in the deposition of a phosphor thin film is the stoichiometric transfer of target material to the substrate. It is well known that the pulsed laser deposition (PLD) can produce a wide variety of complex compounds with controlled composition and properties [4,5]. Y 3 Al 5 O 12 has widely been used as a host lattice for lanthanide ions to produce phosphors emitting a variety of colors, especially in the green emission range [3,6]. As reported by Yousif et al. [5], the brightness and the saturation characteristics of Y 3 Al 5 O 12 were improved by the replacement of a certain percentage of Al with Ga. On the other hand, this replacement slightly increases the degradation rate of the luminescence intensity during prolonged electron irradiation as reported by Katsutoshi et al. [7]. However, Y 3 (Al,Ga) 5 O 12 :Tb phosphor powder, shows very good cathod- oluminescent (CL) stability, during prolonged electron bombard- ment, indicating that, it is a promising candidate for FEDs and other lighting applications [5]. In this study, pulsed laser deposited Y 3 (Al,Ga) 5 O 12 :Tb thin films were grown with fixed processing conditions (substrate tempera- ture, target to substrate distance, oxygen working atmosphere, etc.). Structural, photoluminescence (PL) and CL properties of the Y 3 (Al,Ga) 5 O 12 :Tb thin films annealed at different temperatures are presented. The improvement of the luminescent properties that was attributed to improved crystallinity and stability of the films during electron beam irradiation was recorded. 2. Experimental setup A commercial Y 3 (Al,Ga) 5 O 12 :Tb powder phosphor, obtained from Phosphor Technology [8] was pressed without binders using an in-house built sample holder and was used as an ablation target. The target was annealed at 300 1C for 8 h in air to get rid of all adventitious water containing species that might be present in the pellet and was then placed inside the chamber of the PLD system on a rotating target holder that can also move linearly (up and down). Note that the rotational as well as linear motion of the target rod restricted the laser ablation induced degradation of the Contents lists available at SciVerse ScienceDirect journal homepage: www.elsevier.com/locate/jlumin Journal of Luminescence 0022-2313/$ - see front matter & 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jlumin.2013.04.042 n Corresponding author. Tel.: +27 514012926; fax: +27 514013507. E-mail address: swarthc@ufs.ac.za (H.C. Swart). Journal of Luminescence 143 (2013) 201–206