In this work, controllable hexagonal holes and distributed Er2O3/Er2O3-graphene particles are fabricated on silicon wafers using a straightforward, hydrofluoric, acid-free, and strong alkali-free hydrothermal method. As long as erbium nitrate hydrate and urea coexist in the reaction mixture, silicon wafers can be synthesized successfully using controllable hexagonal hole structures that are regulated by hydrothermal temperature and the addition of graphene oxide and hexadecyl trimethyl ammonium bromide to the reaction mixture. Correspondingly, the wettability of these silicon wafers also is controllable due to the structure that can be changed from hydrophilic (89.3 degrees) to superhydrophobic (153.1 degrees). In short, this work not only provides a simple and nontoxic approach for preparing hexagonal hole structured silicon wafers, but also produces superhydrophobic silicon wafers that potentially can be applied for corrosion-resistant coatings, oil-water separation, and other fields. (C) 2020 Elsevier Inc. All rights reserved.