Magnetron sputtered V2AlC thin films

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Synthesis and elastic properties of V2AlC thin films by magnetron sputtering from elemental targets

This article has been downloaded from IOPscience. Please scroll down to see the full text article. 2009 J. Phys. D: Appl. Phys. 42 185408 (http://iopscience.iop.org/0022-3727/42/18/185408) View the table of contents for this issue, or go to the journal homepage for more

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JOURNAL OF PHYSICS D: APPLIED PHYSICS

J. Phys. D: Appl. Phys. 42 (2009) 185408 (8pp)

doi:10.1088/0022-3727/42/18/185408

Synthesis and elastic properties of V2AlC thin films by magnetron sputtering from elemental targets Darwin P Sigumonrong1 , Jie Zhang2,3 , Yanchun Zhou2 , Denis Music1 and Jochen M Schneider1 1

Materials Chemistry, RWTH Aachen University, Mies-van-der-Rohe-Str. 10, 52074 Aachen, Germany Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, People’s Republic of China 3 Graduate School of Chinese Academy of Sciences, Beijing 100039, People’s Republic of China 2

Received 2 March 2009, in final form 29 July 2009 Published 3 September 2009 Online at stacks.iop.org/JPhysD/42/185408 Abstract The influence of deposition temperature on phase formation of V2 AlC is studied by magnetron sputtering from elemental targets. At substrate temperatures below 750 ◦ C, we observed the formation of Alx Vy and V2 C using x-ray diffraction (XRD) analysis. At 750 ◦ C, a phase pure polycrystalline V2 AlC film on a ∼12 nm thick transition layer has been observed using XRD and transmission electron microscopy. Selected area electron diffraction indicates that the film grown on the transition layer consists of phase pure V2 AlC. As the substrate temperature is increased to 850 ◦ C, the formation of V2 C in addition to the V2 AlC phase is observed. This may be due to desorption of aluminium causing the decomposition of V2 AlC into vanadium carbides and aluminium. The V2 AlC film is fully dense and polycrystalline and the elastic modulus based on nanoindentation is within the expected error margin consistent with previously reported theoretical calculations and the diamond anvil cell measurement of bulk V2 AlC samples.

bulk modulus values determined by various experimental techniques range from 128 GPa to 201 ± 3 GPa [5, 10, 11] and hence exhibit a 36% difference. No explanation for this extensive variation can be found in the literature. Bulk MAX phases can generally be synthesized by hot reactive pressing [2, 12, 13], by pressureless sintering of pre-reacted powders [5] and by solid-state reactions [14, 15]. Thin film syntheses of a wide variety of MAX phases have been reported mostly using magnetron sputtering [7, 16–25], cathodic arc deposition [26] as well as chemical vapour deposition [27–30]. One very important processing parameter in thin film technology is the deposition temperature, because it determines the range of useable substrate materials [24]. The effect of deposition temperature on phase formation has been studied in this work. Depth-sensing indentation was utilized to characterize the elastic properties of the thin films [31]. The elastic property data obtained are in sound agreement with ab initio calculations from [7–10] and this work, as well as previously reported diamond anvil cell data [11].

1. Introduction V2 AlC (space group P63 /mmc, prototype Cr2 AlC) belongs to the so-called Mn+1 AXn phases, where M is a transition metal, A is an A group element (mostly IIIA and IVA), X is either C or N and n = 1–3 [1–4]. These phases contain MX layers interleaved with A layers and exhibit unusual physical properties, including high stiffness [5], good high-temperature oxidation and hot corrosion resistance [6], which are usually associated with ceramics, as well as ductility, and good thermal and electrical conductivity [2]—which are typical metallic attributes. This very unusual property combination serves as a motivation for exploring the structure–property relationships of these materials. Several physical properties of V2 AlC have been reported, based on studies of bulk samples and theoretical calculations. V2 AlC has a density of 4.81 g cm−3 and room temperature thermal conductivity in the range of 25 W m−1 K−1 [5]. Bulk modulus of V2 AlC, calculated using the ab initio method, is reported to be in the range 175–195 GPa [7–10]. The reported 0022-3727/09/185408+08$30.00

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J. Phys. D: Appl. Phys. 42 (2009) 185408

D P Sigumonrong et al

2. Methods In this work, V–Al–C thin films were grown in a co-sputter deposition chamber containing three dc magnetron cathodes equipped with elemental targets. These cathodes were tilted to approximately 40◦ with respect to the substrate’s normal and arranged symmetrically with their normals pointing towards the centre of the substrate—adapted from the arrangement used previously [7, 17]. Vanadium (99.99%), aluminium (99.95%) and graphite (99.9%) targets were sputtered at power density values of 2.83 W cm−2 , 0.94 W cm−2 and 4.71 W cm−2 , respectively. The power density values were kept constant throughout the work. The base pressure was