A miller, a non-transitory computer-readable medium, and a method for milling a multi-layered object. The method may include milling each structural element of an array of structural elements that are spaced apart from each other by gaps to provide the milled structural elements, wherein each milled structural element has a flat upper surface, wherein prior the milling each one of the structural elements of the array has a flat upper surface of a certain width, wherein the certain width is of a nanometric scale. The milling of each structural element of the array may include scanning a defocused ion beam of the certain width along a longitudinal axis of the structural element. A current intensity of the defocused ion beam decreases with a distance from a middle of the defocused ion beam.