Wetting behavior of water on silicon carbide polar surfaces

Technically important wide band-gap semiconductors such as GaN, AlN, ZnO and SiC are crystallized in polar structures. Taking SiC as an example, we investigate the effect of surface polarity on the wetting behavior by water using experiments and molecular dynamic simulations. It is found that the contact angle (CA) of deionized water on the carbon-face (C-face) is significantly larger than that on the silicon-face (Si-face) for both 6H-SiC and 4H-SiC, while the CA of tetrachloromethane is almost the same on these two faces. This finding clearly indicates that polar interactions between water and SiC induce such a large difference in the CA. Extensive molecular dynamics simulations suggest that a larger CA on the C-face than that on the Si-face is resulted from the different charge agglomeration on the two faces. These results will not only be helpful in improving the state of the art processes such as rinsing and wet etching in device fabrication, but also offer a reliable method to determine the polarity of SiC crystals quickly, simply, accurately and nondestructively, which is easily extendable for the measurement of other polar crystals.