Photoinduced deformation of a-C thin films prepared by RF magnetron sputtering

Abstract

A material with photoinduced deformation ability is essential for the development of photomechanical actuators powered by visible light such as the endless solar light. In this study, amorphous carbon (a-C) films were prepared by radio-frequency (RF) magnetron sputtering of a graphite target in an Ar atmosphere and were observed to deform under visible light illumination. The deformation of the non-hydrogenated a-C films with photon irradiation and the rise in temperature due to the photothermal effects were studied using a a-C/ultra-thin SiO2 substrate bimorph specimen. The photoinduced deformation in these films is based on energy conversion from photons to kinetics. With an increase in the deposition temperatures from 473 K to 873 K, the films shifted to graphite-like structures. The temperature of the films under illumination increased with increasing deposition temperature, due to the photothermal effects in the graphite clusters of the films. Meanwhile, maximum deformation was achieved in the film deposited at 573 K, and thereafter deformation decreased with increasing deposition temperature. Carbon-based materials such as carbon nanotubes are known to undergo photoinduced deformation owing to photothermal effects; however, the photoinduced deformation in a-C films occurs via different kinetic pathways without these photothermal effects.