Sensors and Actuators B 126 (2007) 332–337 In-situ study of Ni–Ti thin film growth on a TiN intermediate layer by X-ray diffraction R.M.S. Martins a,∗ , N. Schell b , R.J.C. Silva c , L. Pereira c , K.K. Mahesh c , F.M. Braz Fernandes c a Institute of Ion Beam Physics and Materials Research, Forschungszentrum Rossendorf, P.O. Box 510119, D-01314 Dresden, Germany b GKSS Research Center Geesthacht, Max-Planck-Str. 1, 21502 Geesthacht, Germany c CENIMAT, Campus da FCT/UNL, 2829-516 Monte de Caparica, Portugal Available online 18 March 2007 Abstract Shape Memory Alloy (SMA) Ni–Ti thin films have attracted much interest as functional and smart materials due to their unique properties. However, there are still important issues unresolved like formation of film texture and its control as well as substrate effects. In this study, near- equiatomic films were obtained by co-sputtering from Ni–Ti and Ti targets in a process chamber installed at a synchrotron radiation beamline. In-situ X-ray diffraction during the growth of these films allowed establishing a relationship between structure and deposition parameters. The effect of a TiN layer deposited on top of the SiO 2 /Si(1 0 0) substrate prior to the deposition of the Ni–Ti films was analysed. These experiments show that TiN acts not only as a diffusion barrier, but also induces different crystallographic orientations. A TiN layer with ≈215 nm thickness induces the preferential growth of (1 1 0) planes of the Ni–Ti B2 phase parallel to the substrate from the beginning of the deposition with a constant growth rate during the whole deposition. For a TiN thickness of ≈15 nm, the diffraction peak B2(1 1 0) also appears from the beginning of the deposition but much less intense. In this latter case, the B2(2 1 1) peak was also detected having observed a crossover from 〈110〉 oriented grains dominating at small thicknesses, to 〈211〉 oriented grains taking over at larger thicknesses. The same orientations and similar intensities were observed for a Ni–Ti film deposited on a TiN layer with ≈80 nm. © 2007 Elsevier B.V. All rights reserved. Keywords: Shape memory alloy; Ni–Ti; Deposition by sputtering; In-situ X-ray diffraction; Texture development 1. Introduction Ni–Ti thin films are recognized as an excellent material for use in microelectromechanical systems (MEMS). Their high recoverable strains and large recovery forces coupled with the compatibility with batch-processing technology of silicon micromachining are a plus for the desired merging of the silicon-based microelectronics with micromachining technolo- gies. They can be electrically driven using joule heating and, when compared with the bulk material, they demonstrate fast cooling rates because of their higher surface/volume ratio of materials increasing substantially the heat transfer rate [1–3]. Ni–Ti thin films are usually prepared using a sputtering method and typically deposited on Si and on SiO 2 /Si wafers. ∗ Corresponding author. Tel.: +33 4 76 88 28 72; fax: +33 4 76 88 25 05. E-mail address: rui.martins@esrf.fr (R.M.S. Martins). Although several studies have been published concerning their deposition (e.g. review works [4,5]), there are still important issues unresolved like substrate effects as well as formation of film texture and its control [6]. The inclusion of a buffer layer like SiO 2 is usually expected to act as an electrical and thermal insulating layer to prevent silicide formation, or also as a sacrifi- cial layer. However, it was reported by Fu et al. that a SiO 2 buffer layer serves as an effective diffusion barrier but at the expense of film adhesion [7]. The study of Ni–Ti film deposition on different substrates (such as poly-Si, TiN, Si 3 N 4 , etc.) is thus important for the development of suitable microdevices. Moreover, it will be necessary to establish a relationship between the substrates and texture development. In most polycrystalline materials, crystal orientations are present in a definite pattern and a propensity for this occur- rence is caused by the processing conditions. Many material properties (Young’s modulus, Poisson’s ratio, strength, ductility, toughness, electrical conductivity, etc.) depend on the average 0925-4005/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.snb.2006.12.052