Correlation of photothermal conversion on the photo-induced deformation of amorphous carbon nitride films prepared by reactive sputtering

Abstract

The photo-induced deformation of hydrogen-free amorphous carbon nitride (a-CNx) films was investigated under visible-light illumination. The films gave rise to photothermal conversion by irradiation. In this study, we investigated the effects of thermal energy generated by irradiation on the deformation of a-CNx/ultrathin substrate bimorph specimens. The films were prepared on both ultrathin Si and SiO2 substrates by reactive radio-frequency magnetron sputtering from a graphite target in the presence of pure nitrogen gas. The temperature of the film on the SiO2 substrate increased as the optical band-gap of the a-CNx was decreased. For the film on Si, the temperature remained constant. The deformation degree of the films on Si and SiO2 substrates were approximately the same. Thus, the deformation of a-CNx films primarily induced by photon energy directly.

Photomechanical Response of Amorphous Carbon Nitride Thin Films on SiO₂Substrate

“…Therefore, it is reasonable to surmise that the occurrence of δ t was caused mainly by light. In the case of using the Si substrate, the surface temperature change of the a-CN x films was almost zero because of the higher thermal diffusivity, but the change of δ t was almost similar to the case of SiO 2 substrates [10].…”

“…The maximum value of δ t was obtained by the specimen deposited at 573 K when the incident light was turned on. Although the reason for the maximum value of δ t observed in the a-CN x films deposited at 573 K has not been elucidated yet, we think that the existence of the C≡N triple bonds is necessary for the displacement and, in particular, the structures with the high A i /A n ratio and relatively small graphite cluster size play an important role for the displacement [9,10].…”

“…The detailed measurement system was shown in Ref. 10. A Xe lamp (power 150 W) was used to irradiate the a-CN x films, where the light was concentrated to the width of 3 mm.…”

“…In contrast, photoinduced deformation of amorphous carbon nitride (a-CN x ) thin films under visible light irradiation is completely reversible [9,10]. The deformation of a-CN x films can be obtained by the bending behavior of a-CN x /ultrathin SiO 2 substrate specimens.…”

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

“…Amorphous carbon nitride (a-CN x ) thin films have attracted considerable attention owing to their unique properties, such as high wear resistivity 1 , low friction coefficient 2 , 3 , variable optical bandgap 4 , environment-dependent electrical resistance 5 , and biocompatibility 6 , 7 . Most recently, it was found that a-CN x films exhibit photomechanical response 8 , 9 . This response manifests as temporal deformation under visible light irradiation.…”