Restoration of an AFM Height Image using a Deflection Image at Different Scanning Speeds

Abstract

The principle of the Atomic Force Microscope involves scanning an object using a probing tip that is mounted on the free end of a micro mechanical cantilever. While the sample is scanned horizontally the cantilever deflects. The deflection of the cantilever can be sensed among several methods. For instance, optical beam deflection where this method is often used because of it’s simplicity. While the scanning process of the sample stage, the detected deflection is compared with the set point deflection. Then, the error signal which is the difference between the detected and set point deflection is minimized by moving the sample stage in the Z – direction. At a set point value this closed –loop feedback operation can maintain the cantilever deflection and hence the tip – sample interaction force. The sample surface is approximately traced by the resulting 3D movement of the sample stage. Therefore, usually the topographic image can be formed from the electrical signals which are used to drive the sample stage scanner in the Z- direction. In this paper, the AFM topographic image is constructed using values obtained by summing the height image that is used for driving the Z- scanner and the deflection image with a weight function that is close to 3. The value of has been determined experimentally using trail and error. This method gives more faithful topographic image.