Hydrophobic Cu2O surfaces prepared by chemical bath deposition method

In present work, hydrophobic copper(I) oxide (Cu2O) surfaces were fabricated by chemical bath deposition method. Copper oxide layers on glass slides were coated using copper sulfate as a precursor. To examine wetting properties of copper oxide surfaces, various samples were prepared at different numbers of coating cycles and sintering conditions (temperature, time, and atmosphere). Morphology, composition, and optical absorption of the copper oxide layers were characterized by profilometer, AFM, XRD, UV–Vis photospectroscopy, and water contact angle measurements. It was observed that hydrophobicity decreases by increasing oxygen amount of the sintering atmosphere. In fact, this is the result of an increase in the surface oxygen amount and consequently the increase of surface energy. An optimum thickness and surface morphology is obtained for hydrophobicity of these thin films which are due to air trapping at more narrow valleys and development of the Cassie–Baxter phase. Moreover, the effects of valley’s height and width on the wetting were investigated. It is shown that the width of the valleys is a more important factor in developing the Cassie–Baxter phase than the height of valleys. Furthermore, the obtained results show that all copper(І) oxide surfaces tend to a hydrophobicity behavior after 1 week drying at ambient conditions. The measured water contact angles of Cu2O layers were as high as 112°, without sintering or fatty acid modification. Nevertheless, it was enhanced up to 134° at the optimum sintering condition under nitrogen atmosphere. To the best of our knowledge, this is the first precisely study on wettability of Cu2O thin films prepared by this method at the various preparation conditions.