Images of core-shell structures. (a) Schematic of material vapor on a hexagonally close packed sphere monolayer; (b) material vapor from top side; (c) material vapor form bottom side. (d) The SEM image of the hollow spheres. In (a), θ
2 are the incident angle, and φ
2 are the orientation angle; in (d), the hollow spheres are fabricated with deposition parameters of f
top = f
bottom = 30[45°, 0°] + 30[45°, 180°], and the insets are the corresponding simulated images.