The New Method Of Atomic Force Microscopy And The Development Of Horizontal AFM

In recent years, nano-technology has become one of the most active fields in modern science and technology. The branches of nano-technology include nano-physics, nano-chemistry, nano-electronics, nano-material science, nano-biology, nano-mechanics and narto-measurements, etc. With the development of nano-technology, scanning probe microscopy (SPM), especially atomic force microscopy (AFM), has been the most widely demanded and applied tools for researchers to pursue more ambitious goals, and has actually become the indispensable instruments for nano-scientists and engineers.In this thesis, a new concept of AFM has been put forward, and a new type of horizontal AFM with better performance and wider application has been developed based on the systematic research of its principle and method. The research on the new method of atomic force microscopy and the development of th.e horizontal AFM not only has important theoretical significations, but also has a great prospect for practical applications.A comprehensive review about scanning probe microscopy., especially the history and the status of the development of AFM was presented in this thesis. The interaction mechanism of atomic force between tip and sample was unveiled more clearly with the analysis of the change regularity of force-distance curve. The theoretical research about the light pressure of laser and the gravity exerting on the micro-cantilever was first conducted in this paper: setting up the interacting model and formula of the light pressure, investigating the effects of these factors on the interaction mechanism of atomic force and the performance of AFM, conceiving a method to remove these effects and so on. All of these were the theoretical foundation of developing the new atomic force microscopy and the new type of horizontal AFM system.On the basis of the theoretical researches, we developed the new method andtechnique of the horizontal AFM. The significant characteristics of the new AFM include: (i) it has a horizontally designed probe unit, and the direction of cantilever's weight was perpendicular to the atomic force, thus the effect of cantilever's weight on the imaging quality can be effectively avoided; (ii) it owns a particular path of optical beam deflection method for the measurement of cantilever's displacement. With its minimized structure, the path provides an optimal light-amplifying ratio; (iii) the position sensitive detector (PSD) is just located in front of the visual sight of operator, this makes the observation and operation more easily. Moreover, the horizontal system is much more stable than the conventional one (vertical AFM), which usually has a high center of weight, a poor aseismatic capability, and the weight of the probe unit may potentially make itself creep down along the guide way. For the purpose of precise and effective imaging for different samples, we introduced a novel method to adjust the setpoint of imaging force and provided the calculative formula. A new feedback controlling theory and method of horizontal AFM was also advanced in order to develop an effective, steady and optimum feedback controlling system.In this thesis, a novel and powerful horizontal AFM system was first designed and built for surface observation in nano-technology. The main performances of the AFM were in the advanced level around the world. The probe unit of the horizontal AFM includes a photo-electronic detection unit with a particular optical-beam-deflection path, a regulating block of the setpoint of imaging force, the XY scanner and Z feedbackcontroller, the coarse adjusting and fine adjusting mechanism for the sample approaching to the probe tip. The powerful circuits of preamplifier, as well as the circuits of XY scanner and Z feedback controller were developed. The proportional-integral-differential (PID) controlling method was employed to realize feedback control of the Z piezo. We designed the A/D & D/A interfaces for controlling and data acquisition, and further compiled the powerful software system for con...