Abstract
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 sp3C and sp2C, Isp3C/Isp2C, obtained using soft X-ray emission spectroscopy (SXES). Simultaneously, temporal decrease in the sp3C component under illumination is obtained via SXES.
Highlights
Amorphous carbon nitride (a-CNx) 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]
We investigate the relationship between photoinduced deformation and surface electrical states by comparing two samples, with different amount of deformation, via scanning electron microscopy with Ar+ laser irradiation (SEM-L) and soft X-ray emission spectroscopy (SXES)
Discussion a-CNx films have a compressive stress in nature[9]
Summary
Amorphous carbon nitride (a-CNx) 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]. Azobenezene shows photomechanical reversible response to photo-irradiation with different photon energy which are UV and visible light, or thermal energy[11,12]. Macroscopic large deformation of films containing ordered the organic molecules has been observed[18] Piezoceramics, such as Pb1-xLax(ZryTi1-y)1-x/4O3 (PLZT), deform corresponding to the switching off and switching on of visible light[15]. This response is a combination effect of photoinduced strain and piezoelectricity. For carbon-related materials, carbon nanotubes (CNTs) embedded in polymer films[19,20] have been reported to undergo considerable photoinduced deformation This underlying mechanism is the photothermal effects of CNTs. Photoinduced deformation of CNTs on a polymer film has been reported[21]. This study is a first report of SEM-L which is a new approach to reveal the mechanisms of photoinduced deformation in all materials with photomechanical response
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