Low Energy Oxygen Ion Beam Machining of Ultra Smooth and Sharp AFM Nano-Tips from Single Crystal Diamond Rods

Abstract

Diamond made AFM probe exhibits a long life time as diamond has ultrahigh hardness, ultra high tensile strength and high wear resistance. For the ultra fine machining of diamond tip, focused ion beam (FIB) machining is being widely used but the process is very slow due to one by one processing and ripples are formed on the processed surface. Moreover, the irradiation damage and machining cost are significantly high. Compared to FIB machining, low energy broad ion beam machining (BIBM) is better suitable for the mass fabrication of AFM tips. In this paper, we presented a two stage BIBM process using 1-3 keV O + /O + 2 ion beam for the mass fabrication of ultra smooth and sharp AFM nano-tips from single crystal diamond rods. In order to suppress the ripple formation on the processed diamond tip, the sample was rotated during machining process. In our proposed method, around 100 ultra smooth and sharp AFM nano tips with the apex angle of 50 • and an average tip diameter of 22 nm can be simultaneously fabricated in just 1.5 hour. Moreover, the irradiation damage of the processed tip is also very low due to low energy ion beam machining and chemical etching of the amorphous carbon by the oxygen ions. A simulation model is developed to predict the profile change of diamond tip by low energy oxygen ion beam machining. At last, the mechanisms of fine sharpening and ultra smoothening of the diamond tips are discussed with the help of Witcomb formula and Bradley-Harper (BH) model.