| AVS 56th International Symposium & Exhibition | |
| Thin Film | Wednesday Sessions |
| Session TF-WeA |
| Session: | ALD/CVD: Novel Applications, Mechanical Properties |
| Presenter: | O. Carton, Laboratoire de Physique de la Matière Condensée, France |
| Authors: | O. Carton, Laboratoire de Physique de la Matière Condensée, France M. Lejeune, Laboratoire de Physique de la Matière Condensée, France A. Zeinert, Laboratoire de Physique de la Matière Condensée, France S. Zaidi, Laboratoire Roberval, France F. Lamarque, Laboratoire Roberval, France |
| Correspondent: | Click to Email |
The aim of this work is the elaboration of thin films for optical filtering under mechanical constrains. Our dichroic filters (transmission of one wavelength and reflection of another one) had to be deposited on shape memory substrates, with respect to several conditions:
- low thickness of the filter in order to minimize the weight supported by the substrate
- low internal stress in the structure to limit the mechanical action of the filter on the substrate
- high elasticity in order to preserve a good adhesion when the substrate is strongly deformed
- low light absorption in order to transmit the maximum of energy
The realised structures were made up of the stack of two couples of materials: amorphous hydrogenated silicon (a-Si:H) / silicon dioxide (SiO2), and a-Si:H / amorphous polyacid methacrylic (a-pAM), using the Bragg reflector structure with seven layers only. These materials have been elaborated using two plasma techniques: a-Si:H and SiO2 were deposited by magnetron sputtering and the polymeric layers were deposited by inductive plasma enhanced chemical vapor deposition (PECVD). A brief study of the optical properties as a function of the deposition parameters has been performed for each material, and the chemical structure of the polymer was investigated with FTIR as a function of the RF power forwarded to the plasma. The internal stress of the optical filters has been calculated using the Stoney formula, and structures made up with polymeric layers have shown better mechanical properties than structures with silicon dioxide, with a lower value of residual stress. The elasticity of the realized optical filters has been tested on plastic substrate with a repeatedly deformation applied to the structure, and a good stability has been observed with no significant change in the optical filtering properties before and after the deformations.
The aimed application of these filters is to achieve a chromatic wireless control of shape memory alloy (SMA) micro-actuators. The actuation is performed by the use of two laser sources in order to heat and distort pieces of SMA (Nitinol). This chromatic response was first realised with optical filters on glass substrate, the Nitinol pieces were placed under this glass substrate and the selective response for the different laser wavelengths was observed. Then the optical filters were directly deposited on Nitinol sheet and the selective response was also visualized.