Tagging Atoms by Plasma Treatment

When samples are immersed in water a significant decrease of the contact angle of water is observed. The change from the solid line with open circles to the dotted line with closed circles indicates the extent of contact angle change. The extent of decrease was inversely proportional to the crystallinity of the sample, which indicates that the surface configuration change occurs mainly in the amorphous phase in the surface state, i.e., F atoms attached to the crystalline surface are immobile. 

The change from a closed circle on the dotted line to corresponding open square or closed triangle represents the recovery on drying. The extent of recovery from a water-immersed sample is dependent on how the sample was treated. The heat treatment at higher temperature caused the greater extent of the recovery. The extent of recovery is inversely proportional to the crystallinity in both heat treatments, confirming the trend found on the immersion process. 

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