“…Liquid-phase techniques such as hydrothermal and electrochemical processes have been widely used to grow ZnO structures on ZnO-seeded substrates [7,11,17,[19][20][21], catalyzed substrates [22], or seed/catalyst-free substrates [14,19,21,23]. Generally, the grown ZnO structures on the ZnO-seeded substrates are mostly in the form of onedimensional (1D) nanostructures [7,9,20,21,24,25] due to the nature of chemical reaction of liquid-phase techniques and also due to the small grains and rough surfaces of ZnO seed layers prepared by the sputtering method [7,20,21] or other deposition techniques [9,24,25].…”