Solid State Communications 139 (2006) 522–526 www.elsevier.com/locate/ssc Growth of AlN nanostructures by a rapid thermal process Philippe F. Smet ∗ , Jo E. Van Haecke, Dirk Poelman Department of Solid State Sciences, Ghent University, Krijgslaan 281-S1, 9000 Gent, Belgium Received 28 February 2006; received in revised form 15 June 2006; accepted 14 July 2006 by G. Abstreiter Available online 1 August 2006 Abstract Aluminum nitride nanorods were grown during rapid thermal annealing of multi-layered Al 2 S 3 /BaS thin films. Depending on the thickness ratio between the BaS and Al 2 S 3 layers, nanowires or straight nanorods were obtained. Typical dimensions for the nanorods were a diameter in the range of 50–100 nm and a length of 2–5 μm. The nanostructures are formed upon annealing at a relatively low temperature of 900 ◦ C when aluminum evaporates from the thin film, but remains trapped between the thin film surface and the Si wafer, which is used as a support during the annealing. The nitrogen is provided by N 2 gas flushed through the annealing chamber. High-resolution transmission electron microscopy showed crystalline, wurtzite-structured AlN nanorods. The growth mechanism in terms of thin film composition, annealing parameters and the role of catalysts is discussed. c  2006 Elsevier Ltd. All rights reserved. PACS: 81.05.Ys Keywords: A. Nanostructures; A. AlN; A. BaAl 2 S 4 ; B. Thermal annealing 1. Introduction One-dimensional nanostructures such as nanotubes and nanowires are currently attracting a lot of attention, from both scientific and technological points of view. More specifically, aluminum nitride offers promising properties for future applications, such as field emission displays [1]. AlN nanostructures, both in hexagonal and cubic phases, have already been prepared with several techniques [2], including nitrogen arc discharges [3], gas-source molecular beam epitaxy [4] and thermal chemical vapour deposition [5]. A wide variety of nanostructures have been obtained, whether or not arranged in arrays: nanorods, nanowires, nanorings, nanocones and even Eiffel-tower-shaped nanotips [6]. Cubic AlN nanowires, with diameters of 30–100 nm and lengths up to 700 nm could be prepared with a highly non-equilibrium arc- plasma method, at temperatures of about 6000 ◦ C[7]. 15 nm wide hexagonal nanowires resulted from a reaction at 1100 ◦ C of Al powder in a NH 3 –N 2 atmosphere [8]. The use of Ni as a catalyst yielded narrow and uniform nanowires. Aligned, but polycrystalline nanowires could be grown with the same ∗ Corresponding author. Tel.: +32 9 264 43 53; fax: +32 9 264 49 96. E-mail address: philippe.smet@ugent.be (P.F. Smet). method using a confinement of anodic porous alumina [9]. Recently, AlN nanorings were prepared by evaporating an Al–Mn alloy in a N 2 -NH 3 atmosphere at 1100 ◦ C[10]. In this paper we report the formation of AlN nanorods and nanowires by a specific process of thermal annealing of a multi- layered Al 2 S 3 /BaS thin film. Europium-doped BaAl 2 S 4 thin films are currently studied as blue-emitting phosphor layers in thin film inorganic electroluminescent displays [11]. In order to obtain such films, we implemented a multi-layer technique in which a stack of alternating BaS and Al 2 S 3 thin films is deposited with electron beam evaporation [12]. Up to a substrate temperature of 500 ◦ C, the reaction between the constituent layers is limited, and a post-deposition thermal annealing at 800–900 ◦ C is necessary to obtain crystalline BaAl 2 S 4 thin films. During electron microscopy investigation, AlN nanostructures could be observed on the thin film surface, depending on the annealing conditions. Several deposition and annealing parameters were varied to optimize the formation of nanostructures and, more specifically, to elucidate the growth mechanism of these structures. 2. Experimental procedure Typical multi-layered Al 2 S 3 /BaS thin films consist of 23 alternating layers of BaS and Al 2 S 3 , with a total thickness 0038-1098/$ - see front matter c  2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.ssc.2006.07.017