A new way of calibrating the spring constant by measuring both resonant frequencies of the cantilever in air and in liquid is presented. By relating the two frequency values, the density and viscosity of the liquid, the precise spring constant value can be obtained. As a ondestructive method and without other apparatus, it is an easy way of cantilever calibration especially suitable for the study of ligand-receptor interaction and using AFM in aqueous as well.

The coincidence scanning mode has been developed by analyzing feedback equations for constant-current scanning and imaging surfaces with atomic resolution with the new mode.This mode can be almost applied to the feedback control of all sorts of SPM instruments,and reduces the scanning time to 60%.

Nanoscale oxide structures are very important for the study of functional nanodevices. Local oxidation induced by electric field with scanning probe microscopy is a promising method. Some oxide lines and dots on Si surface were fabricated using conductive atomic force microscope in this paper. Nanoscale oxide lines induced by dc voltages exhibit the characteristic of single peak, but the hollow structures with higher aspect ratio are observed under the effect of square wave voltages. We present the hollow structures result from the finite diffuse speed and concentration of oxygen ion, and the higher aspect ratio results from the effect of dynamic electric field in the conductor-nonconductor-semiconductor junction formed in the course of fabrication.

Studieds of the modification mechanism of Au and Ti surfaces by electric fields applied with a scanning sunneling microscope (STM) are carried out at atmospheric pressure and room temperatute. For pulses of 1-100μs, nanodots can only be formed on Ti under conditions where the current shows substantial fluctuation, indicating tip-sample contace. If the field is applied gradually, Au is not affected and pits are formed on Ti. We interpert pit formation as a result of fiele-induced oxidation. Moreover, experiments show that the relative humidity plays an important part in nanostructure formation on Ti. Our results can be explained through a combination of direct contact and oxidation inducedby electricf field.