nanoTA FAQ

nanoTA probe specification

Q: What is the spatial resolution of a softening temperature of a thermal probe?

Q: What are typical heating rates used in a nanoTA measurement?

Q: What is the lowest Laser Sum voltage required to obtain proper results?

Samples Requirements

Q: What kinds of sample materials are investigated with nanoTA?

Q: What is a maximum surface roughness and slope for a nanoTA measurement?

Q: How does one interrogate the interior or bulk regions of a sample material?

nanoTA temperature calibration

Q: How often must the nanoTA probe be calibrated?

Q: The markings on my nanoTA calibration standard have worn away, how can I tell which standard material is which?

Q: what is the lowest feasible start temperature for nanoTA?

Q: Can nanoTA be performed in sub-ambient or under vacuum?

Questions about the nanoTA heating curve

Q: Why does the resistance data channel look unusual at the start of a ramp?

Q: Why does only the first measurement in my nanoTA TTM produce a good nanoTA measurement but consecutive measurements appear in free air or out of contact?

Q: The Deflection signal is increasing by a few volts during the temperature ramp but appears insensitive to my material transitions. In addition the sample appears heat affected in the optical microscope.

Q: My nanoscale thermal analysis curve stops before reaching the specified end temperature.

Q: Can the nanoTA deflection channel be calibrated into nanometers?

Properly using a nanoTA probe

Q: In which orientation do I connect the thermal probe to AFM+?

Q: What are the most common ways that a nanoTA probe can become damaged?

Q: My nanoTA curve doesn’t expand as I would expect, how can I tell that the probe heating?

Q: How can I tell if the ThermaLever™ probe has been contaminated by the sample?

Q: How should I operate to minimize probe contamination?

AFM imaging with nanoTA probe

Q: Using ThermaLever™ probes, I do not get a large Sum signal

Q: My probe does not image or track the surface well?

Q: When I engage using the ThermaLever probes I see a very strong attraction?

Q: The AFM false engages when using the ThermaLever probes. Why does this occur?

Transition Temperature Microscopy

Q: How long does a TTM take to complete?

Q: What is the minimum spacing of points in the TTM?

nanoTA probe specification

Q: What is the spatial resolution of a softening temperature of a thermal probe?
The thermal probe end radius is better than <30nm. The area of indentation or sample softening is dependent upon the sample and user defined software parameters. In general the average indentation left by a nanoTA thermal probe is ~100nm.

Q: What are typical heating rates used in a nanoTA measurement?
The nanoTA probe can be heating from conventional rates up to 600,000 °C/min. The most common heating rates employed in nanoTA range between 10-50 °C/s.

Q: What is the lowest Laser Sum voltage required to obtain proper results?
The
ThermaLever™ probe is uncoated Silicon typically with a small area at the end of the cantilever. This means there will be less reflected laser light from the cantilever reaching the photodiode and so a smaller Laser Sum signal relative to standard AFM cantilevers. Different AFM systems have different focused laser spot sizes at the cantilever and electronics with different photodiode gain so it is difficult to define a specific value for the minimum Sum value. Typically the Sum value will be ~1/2 the value for a standard uncoated Silicon probe. Some small percentage of probes may not be able to achieve this Laser Sum but will still perform well. If you believe that you are experiencing difficulty with a probe and that the sum intensity is not what you expect then please contact Anasys Instruments support.

Sample Requirements

Q: What kinds of sample materials are investigated with nanoTA?
The nanoTA measurement can only be performed on materials with a lower thermal conductivity such as polymers and organic materials. This is because large thermally conductive masses act as a heat sink to the heat generated by the tiny thermal probe.

Q: What is a maximum surface roughness and slope for a nanoTA measurement?
It is best to perform nanoscale thermal analysis with a surface roughness of approximate 1-2 um or better. Slope should also be minimized as surface tilt may introduce error into the thermal calibration.

Q: How does one interrogate the interior or bulk regions of a sample material?
Many features or defects originate within the interior of a sample material. The nanoscale thermal analysis probes the first 100nm of a surface therefore in order to access interior regions a cross-sectioned method may need to be employmMicrotome is the most common method. When processing a surface for analysis it is important to exercise caution as to not greatly modify the structure such as with energy or heat.

nanoTA temperature calibration

Q: How often must the nanoTA probe be calibrated?
It is recommended that a new calibration is made on each probe every day or after prolonged use. A typical calibration takes about 20 minutes to complete. Although probes should be similar in their heating behavior, each one will have it own unique calibration

Q: The markings on my nanoTA calibration standard have worn away, how can I tell which standard material is which?
The PET is a transparent sheet cut in the shape of a parallelogram. The PCL and PE are pie shaped. In clockwise order the calibration materials are PCL, PE, and PET with a melt of 55° C, 116° C, & 235° C respectively.

Q: what is the lowest feasible start temperature for nanoTA?
Without environmental control the probe start temperature is dependent upon the instrumentation or calibration employed. Laser energy is most often used to track the deflection of an AFM or nanoTA cantilever. This laser energy will typically limit the start temperature by elevating the surrounding sample region above ambient. The quadratic calibration curve that is defined for a given probe may also limit the start temperature. If the start temperature is 50 or higher then it is possible that the calibration was not performed accurately and it is advised to revisit calibration of the common standards.

Q: Can nanoTA be performed in sub-ambient or under vacuum?
Yes, the nanoTA probe may be used under vacuum or at sub-ambient temperatures. When operating at temperatures below the condensation point of water then environmental control will be required so that moisture does not accumulate on measurement surfaces.

Questions about the nanoTA heating curve

Q: Why does the resistance data channel look unusual at the start of a ramp?
This is because the resistance channel is a digitally calculated data channel that involves a division of the probe voltage and probe current data channel. Due to tiny digital and temperature dependent offsets in the electronics, a singularity in the division may manifest as either a +10 V or -10 V resistance output near the start of a thermal ramp. Prior to leaving the factory each nanoTA is calibrated to reach steady state resistance before a heating voltage of 0.2 Volts. (NOTE: This may change over time and with age) It is first recommended to bypass the singularity by starting your temperature ramp at 0.2 V. If you feel that your resistance channel does not reach a steady state by 0.2 V even with a fixed resistor in the place of a probe then
contact Anasys Instruments support for information regarding a recalibration.

Q: Why does only the first measurement in my nanoTA TTM produce a good nanoTA measurement but consecutive measurements appear in free air or out of contact?
TTM or array measurements require the probe to withdraw and reengage into contact with a sample surface. The setpoint is usually determined that will minimize force on the sample when imaging. A sufficiently small force for imaging is often insufficient for reengaging a probe that was pulled out of contact following a nano thermal analysis measurement. Try increasing the force by increasing the setpoint in the positive direction before starting the array measurements.

Q: The Deflection signal is increasing by a few volts during the temperature ramp but appears insensitive to my material transitions. In addition the sample appears heat affected in the optical microscope.
Some samples such as cross linked materials, highly filled composites, and densely packed structures may have a subtle or difficult to discern transition temperatures. An AFM image of the region may reveal a small indentation or penetration. Increasing the setpoint before a nano thermal analysis measurement (e.g. applying more force) may increase the rate of penetration and thereby provide a more distinct change in slope in the nanoTA curve. Ensure that the deflection signal remains near the center and in the linear portions of the photo detector. To increase the range of deflection make the free air target deflection more negative between -7 and 0V deflection. For highly expanding samples, the z-feedback may be required when heating.

Q: My nano thermal analysis curve stops before reaching the specified end temperature.
Check that the triggered aborts are set correctly. If the Minimum temperature is set too low then it is possible that the controller is triggering an abort before reaching a desirable temperature in the thermal ramp. The resistance channel often has digital spikes near ambient temperatures that falsely abort the thermal ramp.

Q: Can the nanoTA deflection channel be calibrated into nanometers?
The default unit for nanoTA deflection is [V] volts however Analysis Studio can plot the data channel in arbitrary units and with scaling. In order to scale or change the units of a nanoTA data channel enter the Channels menu by selecting nanoTA channels from the Setup file menu. Here a user can set the units and scaling to his/her specification. In order to convert the deflection signal from volts to nanometers, the user will need to calibrate the deflection signal. This can typically be done by using a force calibration or force curve mode. In this mode the Z position of the probe or sample is periodically ramped back and forth and a plot of the deflection signal is made. By measuring the change in deflection signal versus the calibrated Z positioned, a deflection sensitivity can be determined. This value can then be used in the Analysis Studio software assuming the deflection signal is equivalent from the AFM software to where the NanoTA2 electronics sample the deflection. It is important to note that the nano thermal analysis measurement is non-isothermal therefore a deflection calibration will not enable the technique to quantify a volumetric change or coefficient of thermal expansion.

Properly using a nano thermal analysis probe

Q: In which orientation do I connect the thermal probe to AFM+?
The probe connector is not sensitive to electrical polarity therefore the probe may be plugged in with either orientation.

Q: What are the most common ways that a nanoTA probe can become damaged?
Just like other AFM cantilevers the tip of the nanoTA probe will dull overtime. By carefully manipulating the probe positiong and forces the lifetime of a probe can be greatly extended. Because the nanoTA probe is frequently heated while in contact with softening materials it is important to closely monitor the probe and to withdraw it from the sample when the probe begins to penetrate into the medium. If the probe becomes contaminated a clean probe routine may be exercised in an attempt to burn off foreign materials. With careful use and by minimizing nanoTA penetration the thermal probe may last for thousands of measurement cycles.

Q: My nanoTA curve doesn’t expand as I would expect, how can I tell that the probe heating?
The first thing to check is if the probe is on the sample surface. A probe in free air will exhibit non-linear behaviors in the deflection signal due to stress caused by heating and optical effects. Note the range of these deflection changes as they will be much smaller than a deflection signal resulting from a tip in contact with a surface. In order to check if the probe is heating the best signal to monitor is the resistance signal. During the temperature ramp, the resistance signal should start close to 1.5 V and then increase as a quadratic with increasing temperature up until the resistance turnaround point. Another option is to measure the resistance of the probe using a multi-meter set in the range of 10kOhm. Do not use auto-ranging multi-meters as they may supply currents which could damage the
ThermaLever probe. If the resistance reads infinite then the probe may be damaged or the wire bonds may be broken that supply electrical connectivity to the cantilever substrate.

Q: How can I tell if the ThermaLever™ probe has been contaminated by the sample?
Probe contamination may manifest as a sudden dullness in the imaging resolution or as an anomalous peak in the nanoTA curve (A double peak in the nanoTA curve can also be attributed to a dual thermal event.) If you suspect contamination of the probe, it is advisable to withdraw the probe at least 100 microns away from the sample surface and to use the Analysis Studio Clean probe function. With this function set the heater voltage at an elevated temperature below the resistance turn around for a Hold Time of one second or less. It is advisable to check the temperature calibration after using the Clean probe routine. If the contaminant is visible in the optical microscope image then the probe may be contaminated beyond repair.

Q: How should I operate to minimize probe contamination?
Probe contamination is a rare occurrence assuming the probe is removed from the sample quickly once the sample has reached its transition temperature. This can be accomplished either by manually retracting the probe quickly once the deflection signal decreases or in an automated system such as the afm+™ by correctly setting and enabling the Triggered Abort parameters. Leaving the cantilever in contact with a material that is above its transition temperature or allowing it to penetrate more than a few hundred nanometers will risk contamination.

AFM imaging with nanoTA probe

Q: Using ThermaLever™ probes, I do not get a large Sum signal
The
ThermaLever probes are uncoated silicon and thin, due to this they do not reflect much laser light. This will cause the Sum signal (the total light incident on the photodetector) to be low. In addition, the probes are glued onto mounts and may have some amount of bend in the cantilever. This may require significant translation of the laser diode and/or the SPM photo detector in order to center the reflected laser spot. Also check that the probe is seated flush in the mount and that the wires are not lifting the mount or changing the angle of the probe. The mounting angle is critical to ensure that the beam deflection laser is reflected back towards the photodiode unobstructed and in its entirety. Try replacing the probe with another one from the pack. Do the remaining probes in the probe pack behave differently? If all or any of the probes are exhibiting strange or troublesome laser alignment behavior contact Anasys Instruments support.

Q: My probe does not image or track the surface well?
The tip may be broken, dull, or contaminated. In the later case one may try to run a clean probe routine as detailed in the manual.

Q: When I engage using the ThermaLever probes I see a very strong attraction?
Polymer samples may have a large surface charge due to processing conditions. This will result in electrostatic forces between the probe and sample which may result in a strong attraction. This can be seen during the engage process because there will be a significant decrease in the deflection. It is best if you use anti-static device to relieve the surface of charge which will allow minimization of the force between the tip and sample.

Q: The AFM false engages when using the ThermaLever probes. Why does this occur?
The ThermaLever wires have wirebonds to make electrical connections to the probe. These wirebonds extend down towards the sample surface when the probe is mounted into a SPM. If the sample surface is higher in the location of the wirebonds they can contact before the tip and cause the system to false engage. Try to always orient the sample such that the higher portion of the sample is away from the cantilever substrate.

Transition Temperature Microscopy

Q: How long does a TTM take to complete?
This depends on the user specified region and resolution. In general a useful TTM result may be interpreted from a TTM resolution of 10×10 point. This would take about 15 minutes to complete. Higher resolution for aestheticism or for greater investigation may be composed of 20×20 points or 50×50 points. This TTM condition could take upward of 2 hours of automated data acquisition to complete.

Q: What is the minimum spacing of points in the TTM?
In the
nanoIR or AFM+ systems a TTM may be acquired in either the AFM mode or in the optical microscope mode. The AFM mode utilizes a precision scan stage where the minimum spacing of a thermal measurement is limited by the area of affect around the nanoTA point. This is typically on the order of 100 nm. The maximum size of the region that can be mapped in the AFM mode is 100×100 um. When extended into the optical microscope mode TTM is then limited by a minimum spacing of 1 um but it can then cover the complete range of the sample stage of 8×8 mm

Click here for more information