Contact Mode Atomic Force Research Articles

Study of Stability of Local Anodic Oxidation on HOPG and Few Layer Graphene Using AFM in Ambient

Local anodic oxidation (LAO) has been performed on highly oriented pyrolytic graphite (HOPG) and few layer graphene (FLG) using contact-mode (CM) atomic force microscopy (AFM) in a controlled humidity chamber. Different types of LAO patterns, namely, protrusion and trench features were observed for different tip speeds under similar conditions of LAO patterning, in both CM and noncontact-mode (NCM) AFM images. Observed LAO patterns show a variation in their dimensions over time. This paper carries out a study performed on the observed changes in dimensions of LAO patterns made on HOPG and FLG over several days, pointing to the dynamics of these LAO patterns. The stability of the LAO patterns on HOPG is compared with that for FLG. LAO patterns on HOPG show a widening and reduction in depth over a day. LAO patterns on FLG show, in contrast, a random variation in the lateral dimension “width” and stabilization in the vertical dimension “depth” over several days.

Optical Sensing Limits in Contact and Bending Mode Atomic Force Microscopy

Interferometry and optical deflection offers the best force sensing accuracy using standard cantilever probes in atomic force microscopy. Here, we examine the mechanics of cantilever deformation in the bending and contact mode and the optical sensing principles involved. Under typical conditions, the optical deflection method was found to require displacement measurements that were a thousand times less accurate in order to sense the same amount of force as compared with interferometry used in the regular mode. It also allowed better positioning tolerance for the probe beam in order to retain a high level of accuracy in force sensing. These and other attendant findings serve to provide a clearer outlook for the development of improved accuracy sensors in atomic force microscopy in the contact and bending mode.

Characterizing Spin Finish Layers on Polypropylene Fiber Surfaces by Means of Scanning Force Microscopy Techniques

For a better understanding of the structure, distribution, and composition of spin finish layers on fiber surfaces, scanning force microscopy techniques are used to image spin finish layers on polypropylene fiber surfaces with submicrometer resolution. The polypropylene staple fibers are made into nonwovens, and common antistatic, wetting, and hydrophobizing agents are the spin finishes. Distribution and thickness profiles of the wax-like antistatic and hydrophobizing agents are successfully measured with con tact mode atomic force microscopy and lateral force microscopy. Nanometer scale measurements of local adhesion forces and elastic moduli of the spin finish layer sur faces by force modulation techniques (pulsed force mode) provide further information on the distribution and composition of the spin finish layers. In addition, the oil-like wetting agent layer, which is too soft and sticky for contact mode measurements, can be imaged with the pulsed force mode technique.