| 摘要 |
A system for direct calibration of an atomic force microscope. The tip-sample distance is calibrated by detecting oscillations in the tip-sample interaction forces as a function of tip-sample distance upon approach, oscillations originate from well defined steric forces due to packing effects of solute molecules well before the tip is even in contact with the sample. Apparent heights may be calibrated for sample elasticity, by depositing "hard" e.g. 5nm gold or even smaller Si02 nanospheres as in-situ nanometric test objects. Nanoparticles may also be adhered electrostatically to the probe tip thus providing a well defined imaging tip. The effective temperature on the sample surface may be standardized by 2-dimensional crystallization of Si02- (or other) nanoparticles suspended in water forming 2-dimensional opal crystals. Tip pressure or lateral tip loading forces may be calibrated using pressure-induced phase transitions of material such as of a CaCO3 crystal from the calcite to the aragonite structure. Calibrated AFM may then be applied to performing measurements on biological objects. |
