Phase variation experiments in non-contact dynamic force microscopy using phase locked loop techniques

• Published in: Applied surface science Vol. 140; no. 3; pp. 287 - 292
• Main Authors: Loppacher, Ch, Bammerlin, M., Guggisberg, M., Battiston, F., Bennewitz, R., Rast, S., Baratoff, A., Meyer, E., Güntherodt, H.-J.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 01.02.1999; Elsevier Science
• Subjects: Atomic force microscopes; Condensed matter: structure, mechanical and thermal properties; Damping; DFM; Dynamic force microscopy; Exact sciences and technology; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Non-contact AFM; Phase locked loop; Phase variation; Physics; PLL; Scanning probe microscopes, components and techniques; Solid surfaces and solid-solid interfaces; Structure and morphology; thickness; Surface structure and topography; Surface structure of metal; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Thin film structure and morphology; True atomic resolution; Damping; 61.16.C; 07.79.L; PLL; True atomic resolution; Dynamic force microscopy; DFM; Phase variation; Non-contact AFM; Surface structure of metal; Phase locked loop; APN; Thin films; Atomic force microscopy; Inorganic compounds; Microscope tips; Phase shift; Tip surface interactions; Experimental study; Atomic structure; Ultrahigh vacuum; Sodium chlorides; Non contact measurement; Surface structure
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/S0169-4332(98)00542-X

This work presents constant amplitude Dynamic Force Microscopy (DFM) measurements under ultra-high vacuum conditions performed with home-built digital electronics based on the principle of phase locked loop (PLL) techniques. In DFM so-called topography is often measured in constant frequency shift (Δ f) mode. This study describes the influence of phase shifts on constant Δ f imaging. Therefore, phase variation experiments were acquired, leading to information about the cantilever resonance behaviour close to the surface. As sample, an evaporated thin film of NaCl on a Cu(111) substrate was chosen in order to obtain a heterogeneous system with clean Cu and NaCl areas. The atomic structure of both materials was resolved, which is the first time true atomic resolution was obtained on a metal. Large apparent topography variations are observed on this heterogeneous sample when changing the phase between the excitation and oscillation of the cantilever end. Such artefacts can be explained by comparison with phase variation experiments.