Realization of depth reference samples with surfaces amplitudes between 0.1 nm and 5 nm Annemarie Finzel, Gregor Dornberg, Stephan Görsch, Martin Mitzschke, Jens Bauer and Frank Frost EPJ Web Conf., 215 (2019) 03004 Published online: 10 September 2019 DOI: 10.1051/epjconf/201921503004