Nanotip arrays are formed by exposing a substrate to a process gas mixture that simultaneously forms nanomasks on the substrate surface and etches exposed portions of the substrate surface to form the nanotip array. Components of the process gas mixture form nanocrystallites on the surface of the substrate, thereby masking portions of the substrate from other components of the process gas mixture, which etch exposed portions of the substrate. Accordingly, nanotip arrays formed using this technique can have nanocrytallite endpoints.