Non-uniform Excitation States in Photoinduced Deformation of Amorphous Carbon Nitride Films

Amorphous carbon nitride (a-CNx) films prepared via reactive radio frequency magnetron sputtering deform under on-off visible light illumination. We investigate the relationship between photoinduced deformation and surface electrical states via scanning electron microscopy with Ar+ laser irradiation (SEM-L). Two samples with different levels of photoinduced deformation are prepared. For the film with small photoinduced deformation, uniform secondary electron emission is observed on the film surface, regardless of whether the laser is on or off. On the a-CNx film, which has fifty times larger photoinduced deformation than the previous film, light and dark patches, similar to a speckle pattern, appear on the film surface in SEM-L images. This anomalous phenomenon indicates non-uniformity of the electrical states excited by laser light irradiation. A size of the patches is well correlated with an inhomogeneous distribution of sp(3)C and sp(2)C,I-sp3c/I-sp2c, obtained using soft X-ray emission spectroscopy (SXES). Simultaneously, temporal decrease in the sp(3)C component under illumination is obtained via SXES.