A method involving ion milling is demonstrated to fabricate open-nanoshell suspensions and open-nanoshell monolayer structures. Ion milling technology allows the open-nanoshell geometry and upward orientation on substrates to be controlled. Substrates can be fabricated covered with stable and dense open-nanoshell monolayer structures, showing nanoaperture and nanotip geometry with upward orientation, that can be used as substrates for SERS-based biomolecule detection.