Combinatorial Thin Film Synthesis

Synthesis of polycrystalline and epitaxial metal alloys thin films is a core area of expertise in the Takeuchi Lab at the University of Maryland (UMD).

In particular, co-sputtering tools are available for combinatorial synthesis of metallic alloy thin films. Shape memory alloys that display the elastocaloric effect can be synthesized in thin film forms to investigate various intrinsic properties. These include their lattice constants, transformation temperatures, and thermal hysteresis. Previously, the co-sputtering tools have been used to fabricate composition spreads of shape memory alloys and ferromagnetic shape memory alloys. On 3-inch wafers, ternary composition spreads mapping large fractions of ternary compositional phase diagrams can be generated by non-confocal co-sputtering. A physical shadow mask is used to place grids on the spreads, so that spatially-addressable composition mapping can be created on each wafer. The composition spreads can be deposited at room temperature and then annealed subsequently in vacuum for crystallization or they can be directly deposited at high temperatures. The main aim of the combinatorial investigation within CaloriCool is to identify compositions of shape memory alloys with:

• Low thermal hysteresis
• Low austenite finish temperature
• Large latent heat
• Low critical stress for superelastic transition