Dresden 2009 – scientific programme

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DS: Fachverband Dünne Schichten

DS 9: Metal Layers

DS 9.3: Talk

Tuesday, March 24, 2009, 10:00–10:15, GER 37

Scaling and stress effects on freestanding and substrate-attached TiNiCu thin film microbridges — •Dennis König, Michael Ehmann, Sigurd Thienhaus, and Alfred Ludwig — Ruhr-Universität, Bochum, Deutschland

TiNiCu shape memory alloys are known for their high inherent energy density and their small thermal hysteresis. Therefore, TiNiCu thin films are promising candidates for actuator materials in micro electrical mechanical systems. Due to the difference of the thermal expansion coefficients of the thin film and the substrate, after deposition and subsequent annealing, thin films are under stress. This affects the transformation temperatures. The stress-dependency of the TiNiCu phase transformation was investigated by comparing substrate-attached and freestanding thin film bridges utilizing temperature-dependent resistivity measurements. A difference of over 30 K in the transformation temperatures of freestanding and substrate-attached film was observed. Furthermore it was found that a change of the lateral dimensions of the bridges also causes a shift of the transformation temperatures. With regard to a further miniaturization of the micro-bridges to the nanometer scale, the bridges were reduced in width by focused ion beam. The phase transformation behavior was again characterized using temperature-dependent resistivity measurements. It was found that reducing the bridge width from 4 µm to 1 µm leads to a transformation temperature shift of over 30 K.