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Probe calibration is the basis of accurate atomic force microscope (AFM) measurement. In white light interference based AFM (WLI-AFM), the relationship between the vertical displacement of probe and the position of the interference fringes on probe cantilever should be calibrated for accurate measurement. In this paper, a traceable probe calibration method for WLI-AFM is proposed. A high resolution displacement measurement system based on laser interference is constructed to obtain the vertical displacement of probe with high accuracy. This system is used for standard displacement input for calibration and makes the measurement result traceable to optical wavelength. A zero-order fringe positioning algorithm is presented to determine the position of the interference fringes on probe cantilever. A probe deflection model is established for the calibration relationship which is continuous and can be used for measurement. While calibration is conducted, series of zero-order fringe positions are obtained corresponding to the probe displacement inputs. The data are processed by the probe deflection model to obtain the calibration relationship. The proposed method is applied in a self-developed WLI-AFM. It is verified that the accuracy of the method is higher than the previous methods by certain experiments on this WLI-AFM. [ABSTRACT FROM AUTHOR]

The dynamic characteristics of an atomic force probe are important for rapid and accurate measurement in white light interference (WLI) based atomic force microscope (AFM). The tip of the probe will fly from the surface when its dynamic characteristics are poor, which will cause measurement error. Generally such tip flight can be avoided by reducing the scanning speed, which will decrease the error at the cost of measurement efficiency. In this paper, a dynamical model of atomic force probe is presented to analyze the causes of tip flight in the measurement process. A numerical simulation is performed on a typical sample surface to investigate the influence of profile, preloading and probe parameters on scanning speed. Experimental testing is conducted on a self-developed WLI based AFM, and the experimental results agree well with that of the theory. The maximum scanning speeds of the probe for a sample are tested under certain conditions. It is shown that for a certain probe, the tip flight occurs at the upwards points of the measured sample when the scanning speed exceeds the critical speed, which is constrained by the preloading. [ABSTRACT FROM AUTHOR]

In white light interference based atomic force microscopy (WLIAFM), the vertical displacement of the probe is obtained by zero-order fringe positioning on the probe cantilever, so the accuracy of zero-order fringe positioning will affect directly that of the WLIAFM. However, due to non-uniform distribution of light intensity and photoelectric noises, accurate zero-order fringe positioning becomes a problem. In this paper, two algorithms are proposed to improve the zero-order fringe positioning accuracy. In the first algorithm which is called improved maximum algorithm, multi-row maximum positions of the interference fringes are obtained and error theory is applied to eliminate erroneous maximum positions, then the average of remaining maximum positions is used as the zero-order fringe position. Another is called phase evaluation algorithm, in which wavelet transform is applied to eliminate effects from disturbances mentioned above and Hilbert transform is used for phase evaluation to obtain the zero-order fringe position. The practicability and accuracy of the two algorithms have been verified by series of experiments. The experiment results indicate that both two algorithms are suitable in this condition and the phase evaluation algorithm has higher accuracy while the improved maximum algorithm has higher processing speed. [ABSTRACT FROM AUTHOR]

• A new profilometer is proposed for rapid positioning and measurement of nano-scale structures in large-scale ultra-precision surfaces. • A tracking measurement method is proposed to improve the measurement range of the atomic force microscope (AFM) mode. • A prototype profilometer is established to demonstrate its measurement performance. Characterizations of nano-scale structures using conventional stylus profilometer and optical microscopy are respectively restricted by tip radius and diffraction limit. Atomic force microscope (AFM) can measure smaller structures but it is difficult and time-consuming to find them in large-scale ultra-precision surfaces. In this paper, a new profilometer for rapid positioning and measurement of nano-scale structures in large-scale ultra-precision surfaces is proposed. A technique based on white light interference is integrated into an AFM to detect probe deflection. The adapted profilometer has two measurement modes: a white light interferometry mode used to find an area of interest, an AFM mode for high-resolution measurement. Using this profilometer, the time of positioning an area of interest can be significantly reduced and the measurement efficiency is thus improved. Furthermore, a tracking measurement method is proposed to improve the measurement range of the AFM mode, which can enhance the measuring ability of the profilometer for complex large-scale surfaces. Experiments demonstrate that the profilometer can quickly positioning nano-scale structures in large-scale surfaces and achieve three-dimensional measurement with nanometer resolution. [ABSTRACT FROM AUTHOR]