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Hi
I'm using TESPA probe (k: 42N/m) to measure Young's Moduls of HOPG material that I bought. There is a QNM sample (HOPG), so first I needed to calibrate with this sample via relative method. I found that in the QNM manual, suggested probes for HOPG was TESPA, diamond in chapter 3. Later I found that in the QNM manual chapter 1 (5 pages), RTESPA was recommended for materials with modulus b/t 200MPa and 2000MPa. Which one is correct?
When I tried to get above 2nm deformation for HOPG QNM sample with different setpoints, I couldn't get it. I only get 0.5~1.5 nm deformation even if I increased setpoint a lot. Is it due to the incorrect probe. I think deformation should be increased if I increased the setpoint, right? If it is not appropriate probe, what probe do you recommend? DNISP-HS is enough for materials with Modulus b/t 1GPa to 50 GPa ? Diamond tip is very expensive, so we are looking for the probe that fits for our sample.
Also, for the last relative method calibration, we need to adjust the Tip Radius parameter until the DMT modulus data matches the known sample value. Let assume that I match the DMT modulus matches the known value even though the Tip Radius is considerably larger or smaller than the probe spec. value that I can find on the website. Is it ok? Or should I get similar range of Tip radius with the probe spec. value of Tip Radius ?
Last, let's say I finished the calibration well. Then, I need to adjust the PeakForceSetpoint until the avg. deformation data is equal to that used to image the standard sample. I usually saw a lot of fluctuation of deformation data on the deformation channel. How can I get the avg. deformation data from that ? Do you think this deformation fluctuation is caused by non-flat surface, or characteristics of composite material ?
Thanks for your help in advance.
Shin
Hi, Shin,TESPA or RTESPA is ok but maybe TAP525 is better, it's not that expensive as diamond probe but stiffer than normal tapping probes. you don't need to achieve 2nm deformation on hard materials, ~1nm is still ok for good modulus measurement. You didn't get larger deformation when you increase the setpoint just because your cantilever was not stiff enough. In relative method, tip radius is not physical 'tip radius' anymore, it consists of sources of errors coming from deflection senstivity and spring contant calibrations, it may vary very far from the specified number, no need to be bothered by that. For averaged deformation, you can just look at the mean of the modulus image in the analysis software, usually composite materials will contribute more variation of deformation than topography induced changes.
Ang Li