ELECTROMECHANICAL MICRO-ACTUATOR BASED ON GADOLINIUM-DOPED CERIA

Gd-doped ceria (GDC), extensively studied oxygen ion conductors, was found to exhibit electrostriction effect which is comparable with those of the best electromechanical lead-based materials known. GDC is completely inert with respect to Si, which makes it very attractive for integrated MEMS applications. Using only Si-compatible processes, we fabricated large area (2 mm diameter) self-supported films (0.5-1 μm) of GDC with top and bottom Al contacts.

Application of alternating voltage (AV) induces electromechanical response at the double frequency, which is typical for electrostriction, with a vertical displacement of a few µm. Surprisingly, the response persists till at least 1MHz. The strain generated by AV of 10V (200 kV/cm) at frequency of 1MHz is approximately 0.02% in GDC with 10% Gd doping, which corresponds to electrostriction strain coefficient of »5·10^-19 [m²/V²]. At this value of strain no degradation or fatigue was detected.

Using a proximity sensor, we determined that the amplitude of the displacement at the 2^nd harmonic is linearly proportional to the applied electric-field-squared, at least till 200kV/cm. This implies that the saturation field for GDC is above this value. Our results strongly suggest that GDC is a very promising material for electromechanical actuation in MEMS, in particular for mechanical switches and tunable capacitors.