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Probe and Sample Setup

The High Temperature Heater and –35ºC to 100ºC Heater/Cooler have been extensively tested imaging polymer samples in TappingMode, but can also be applied to studies of other materials and in other modes.

Probes

Uncoated etched silicon probes work best for heating/cooling in a gas environment. Bi-metallic or coated probes may produce unwanted heat-induced bending.

NOTE: Due to inherent mechanical characteristics of the specialized probe holder necessary for this imaging mode, reduced closed loop X IGain and Y IGain parameters are necessary.
  1. Select Calibrate > Scanner > X-Y... from the main menu. The OptoXY Closed Loop Calibration dialog will open.
  2. Set X IGain and Y IGain to 8.
  3. Click OK to close the window and continue with your experiment.

Ensure that you reset the parameters to their default values (12) when using the standard air tapping or TR holder.

Samples

Thin films on a small (1/4 inch, or 6.3 mm diameter) metallic puck are most suitable for AFM studies at elevated temperature. In such cases, the sample temperature is closer to that measured by the heater thermocouple. Larger pucks and thick samples can be placed on the heater surface, but keep in mind the limited power output of the heater and the possibility of the sample temperature being less than that indicated by the heater thermocouple. Figure 1 shows a typical comparison of sample vs. stage temperature.

Figure 1: Sample temperature vs. stage temperature

A magnet incorporated in the heater element holds the metallic sample puck to the heater surface. Samples consisting of a film on a flat substrate (such as mica, a silicon wafer, graphite, etc) or a small block of material with a flat top surface, should be glued to the puck. Choice of glue can be significant for imaging at temperatures above 100°C. Epoxy-based glues may contain volatile components or may decompose in the heat. An exuded material condensed on the window of the heater/probe holder can reduce the window's transparency, thus disrupting the laser beam. Heating the probe prevents condensation of volatile material on the cantilever itself. Low molecular weight materials, which are often added to industrial polymers, may alter the polymer surface being imaged. For example, industrial polypropylene contains a constituent that appears as large droplets on the polymer surface at high temperatures (but below the polymer melting point).

NOTE: You may need to clean the probe holder if material has condensed onto it.

Larger Samples

Larger samples require that a heater/cooler cover with matching sample puck be placed on top of the Heater/Cooler element:

Figure 2: 12 mm (left) and 15 mm (right) Heater/Cooler Covers on the Heater/Cooler Element

Smear Wakefield Thermal Compound, from Wakefield Engineering (part number 120-2) on the mating surfaces (small tungsten cap and small surface under the covers) before putting the components together.

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