Reversible photo-induced deformation of amorphous carbon nitride thin films

•We report a reversible photo-induced deformation in amorphous carbon nitride film.•Amorphous carbon nitride films were prepared by reactive RF magnetron sputtering.•Internal stress was released during a visible light irradiation.•Increasing optical band gap will increase photo-induced deformation.•With increasing sp2 cluster size, photo-induced deformation was inhibited.

A reversible photo-induced deformation was found in amorphous carbon nitride (a-CNx) thin films prepared by reactive radio frequency magnetron sputtering method. The a-CNx films were deposited on a rectangular shaped ultrathin Si substrate at different temperatures in the range of room temperature (RT) to 600 °C. A deflection of a-CNx/Si bilayer system was measured using optical cantilever technique with laser light. The bending signal indicates contraction of the film under illumination. The deflection increased with increasing the intrinsic stress of a-CNx films. An increase the ratio of deflection to the intrinsic stress corresponds to an expansion of optical band gap. As a result of Raman spectra, the photo-induced deformation was found to be inhibited with increasing sp2 cluster size.