Deformable micro-mirror exploits PZT films

11 Oct 2007

Researchers from Zhejiang University, China, have used a simple and inexpensive method to fabricate a novel deformable micro-mirror.

The deformable micro-mirror built by the Chinese team is mainly composed of a silicon-based lead zirconate titanate (PbZr₅₃Ti₄₇O₃, or PZT) film and is fabricated using a simple and reliable sol–gel method (J. Opt. A: Pure Appl. Opt. 9 1014–1018).

Several methods exist to fabricate PZT thin films. The sol–gel technique is one of the most promising and widely used techniques for PZT film fabrication because of its low cost, high purity, large deposition area and easy composition control.

The researchers chose heavily doped silicon for the bottom electrode, which was then coated with a layer of lead titanate (PbTiO₃, or PT). The sol–gel method and a rapid thermal process were used to fabricate the PZT film on top of the PT buffer layer, and the top electrode was a film of aluminum that was evaporated onto the PZT film.

The innovative mirror design uses the converse piezoelectric effect of PZT, and deformation of the new micro-mirror can be achieved by changing the thickness of the PZT film by controlling the applied voltage. The deformation of the PZT thickness was tested with a digital interferometer, and the researchers showed that the micro-mirror could be used in an adaptive optical system.

The new micro-mirror has the advantage of small size, light weight and fast response time over conventional micro-mirrors that are based on the bimetal thermal effect or electrostatic force principle.