Interface Properties of Al/Ni Multilayers as Deposited and Following Volume Combustion Synthesis
- PDF / 610,026 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 67 Downloads / 168 Views
AA4.7.1
Interface Properties of Al/Ni Multilayers as Deposited and Following Volume Combustion Synthesis M. Holtz1,2, D. Aurongzeb,1,2 M. Daugherty,2,3 A. Chandolu,2,4 J. Yun,2,4 J. M. Berg,2,3 and H. Temkin2,4 1
Department of Physics, 2 NanoTech Center, 3 Department of Mechanical Engineering, and 4 Department of Electrical Engineering Texas Tech University, Lubbock, Texas 79409
ABSTRACT We report a volume combustion synthesis study of Al/Ni multilayers. The alternating layers of pure Al and pure Ni were grown on silicon and glass substrates using electron beam evaporation. Layers of equal thickness and with bilayer period of 50 nm were grown with total thickness to 1 µm. We focus in this study on the interface properties of as deposited and following anneals up to 660ºC with 100ºC intervals. Anneal duration was generally 10 min with longer anneals to verify consistency with previously published results. Interface structure was probed using X-ray reflectivity (XRR). Based on interface roughness, we identify three temperature ranges. In the asdeposited to 260ºC range the interface properties remain intact, as seen from the XRR interference fringes beyond the critical angle. From 360 to 460ºC fringes disappear, indicating the loss of smooth interface morphology. The third temperature range is 500 to 560ºC in which the XRR interference fringes are clearly seen, signifying the presence of layering. We describe these results based on a model in which alloy domains form at the interface and grow with temperature and time. Differences in lateral and vertical growth rates of alloy domains are naturally taken into account. At 660ºC, the melting temperature of Al, and above the fringes completely vanish. X-ray diffraction is used to identify the nickel aluminide compounds formed upon anneal. INTRODUCTION Intermetallics of aluminum and nickel have drawn considerable attention due to their technological importance for corrosion and oxidation resistant coatings [1,2], preparation of such materials by self-propagating high-temperature synthesis [3,4], and in metallization for microelectronics [5,6]. One method of producing precursor materials and studying formation properties is to deposit multiple layers of pure Ni and Al with short bilayer periods. Thin layers facilitate reaction through high surface area to volume ratios. Annealing the multilayers from room temperature to the Al melting point (660ºC), but well below that of Ni (1453ºC), produces interesting results due to the variety of possible stable alloy phases, the energetic release due to solid-state reactions, interface dynamics during intermixing, and surface properties. At low temperatures Ni primarily diffuses into Al [7-9] so that Al-rich nickel aluminides are expected. The release of energy which accompanies these solid-state reactions has been studied using differential scanning calorimetry (DSC) [8-10]. Ma et al. performed DSC measurements on Al/Ni multilayers having variable bilayer period from 10 to 150 nm [9]. They find two exothermic features which systema
Data Loading...
