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Metrology & Instrumentation: Polymer Imaging


AFM Probes For The Studies of Polymer

A choice of AFM probes for imaging of polymer samples is often related to a particular application a researcher have in mind. Generally, contact mode measurements are performed with probes whose stiffness varies in the 0.06 � 1 N/m range. Since introduction of contact mode AFM, triangular Si3N4 probes were applied for imaging in the contact mode. In addition to these probes, there are a number of etched Si probes with low stiffness (below 1 N/m) that also can be applied for imaging in the contact mode. Tip apex of the silicon probe is generally smaller than that of the silicon3 and nitrate4. Therefore hybrid probes (Si3N4 cantilever plus Si tip) might be a good choice for high resolution imaging in contact mode.


Stiffer probes are needed for TappingMode experiments. This is related to the fact that contrary to the operation in contact mode, in TappingMode the probe should be withdrawn from a sample in every cycle. In measurements at ambient conditions, tip-sample adhesive and capillary forces need to be overcome during this procedure and, therefore, the probe should be stiffer. Typically, etched Si probes with stiffness ranging from several N/m to tens and even hundreds of N/m are used in TappingMode experiments. On surfaces with low adhesion, TappingMode can be performed with probes of low stiffness (0.1 N/m - 1.0 N/m). It is worth noting that optimization of imaging of polymer samples might require a use of probes with different stiffness. Use of etched Si probes without any special coatings is preferable because coatings might be deposited on a probe apex leading to undesirable increase of its size. Yet for Electric Force Microscopy and Scanning Potential Microscopy one needs to apply Si probes with conducting coatings. For high temperature studies one should avoid the use of a coded tip cantilever which might exhibit undesireable bending due to bimetallic effect.