Pulsed-Laser Deposition of TiNi Shape Memory Alloy Thin Films
- PDF / 293,188 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 64 Downloads / 255 Views
Pulsed-Laser Deposition of TiNi Shape Memory Alloy Thin Films X.Y. Chen, Y.F. Lu1, Z.M. Ren, L. Zhang, J.P. Wang, T.Y.F. Liew Laser Microprocessing Laboratory, Department of Electrical & Computer Engineering and Data Storage Institute, National University of Singapore, 10 Kent Ridge Crescent, Singapore 119260 ABSTRACT Thin films of TiNi shape memory alloy (SMA) have been prepared by pulsed-laser deposition (PLD) at different substrate temperatures. The stoichiometry, crystallinity, and morphology of the deposited films were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and atom force microscopy (AFM). The transformation behavior and crystallization temperatures were investigated by differential scanning calorimetry (DSC). It is found that the Ni content of the deposited films ranges from 46.7 to 52.0 at.%. The crystallization temperature of the amorphous films is around 460°C. The activation energy of the crystallization process is determined by Kissinger’s method to be 301 kJ/mol. The martensitic transformation temperature of the annealed Ti-51.5 at.% Ni film is –20.8°C. INTRODUCTION The shape memory alloys (SMAs) are well known for the shape memory effect (SME), which is a desirable characteristic for microactuators in microelectromechanical systems (MEMS). Titanium-nickel (TiNi), which has attracted great research attention, is recognized as one of the most promising SMAs due to its fascinating properties such as large deformation, large recovery force, high corrosion resistance, excellent fatigue behaviour and low power consumption. TiNi SMA thin films are usually deposited by DC or RF magnetron sputtering. It was concluded that sputter-deposited films possess the shape memory effect and superelasticity comparable with the bulk [1]. Recently, pulsed-laser deposition (PLD) is increasingly being used to prepare a wide variety of materials in thin film form. For many materials, PLD has been established as a simple, reliable and fast technique that offers a great experimental versatility. K. Ikuta et al [2] also suggested that PLD of the TiNi SMA thin films can realize the reduction of the contamination and the match in the composition between the target material and the deposited films. In this study, TiNi SMA thin films were fabricated by PLD.
EXPERIMENTAL DETAILS TiNi thin films were deposited on Si(100) substrates or glass substrates in a PLD system with a background vacuum of 1.0 × 10-5 Torr. A KrF excimer laser (λ = 248 nm, τ = 30 ns) was used as the light source to ablate an equiatomic TiNi disk target. The target-to-substrate distance was approximately 4 cm. The laser pulse repetition rate was 10 Hz. The laser fluence was set between 2.5 and 5.0 J/cm2. The composition of the films deposited on Si(100) substrates at different substrate temperatures was determined by X-ray photoelectron spectroscopy (XPS). The crystal structures 1
Contact author: email: [email protected]; fax: +65-779-1103
O10.12.1
were investigated by a Cu K radiation (λ = 0.15418 nm) X-ray diffraction
Data Loading...
