AFM Principles and Applications

Riquicha A.A.G. et al. 2001. Manipulation of Nanoscale Components with the AFM Principles and Applications, lEEEInt. Conf Nanotechnol, Maui, HI, October 28-30,2001. 

On the other hand, optical microscopy, confocal microscopy, ellipsometry, scanning electron microscopy (SEM), scanning tunneling microscopy (STM), atomic force microscopy (AFM) and total internal reflection fluorescence (TIRF) are the main microscopic methods for imaging the surface structure. There are many good books and reviews on spectroscopic and chemical surface analysis methods and microscopy of surfaces description of the principles and application details of these advanced instrumental methods is beyond the scope of this book. 

Thus, the STM reveals itself as a powerful structural technique to be added to already standard ones routinely in use in the different research fields. The same can be stated for the Atomic Force Microscopy (AFM) as it has proved the same capabilities to study either conducting or insulating disordered surfaces [48]. Finally, it should be noted that STM also presents capabilities to analyze the electronic structure of the surface and to modify the surface. These applications have not been considered in this text but the main principles and examples can be found in the literature [2, 16]. 

In this chapter, attention is focused on in-situ STM and AFM, and recent advances of in-situ SPM in surface electrochemistry and nanoelectrochemistry are introduced, with applications that include surface characterization, nanostructuring, and molecular electronics. First, a brief discussion of the principles and features of STM and AFM is provided, and this is followed by some selected examples of the capabilities of both techniques in the study of surface and nanoelectrochemistry, mostly acquired in recent studies conducted by the present author s group. Emphasis is placed on the roles of in-situ STM and AFM from a methodological point of view. Finally, the prospects for the further development of in-situ SPM are reviewed. 

The very new techniques of scanning tunnelling microscopy (STM) and atomic force microscopy (AFM) have yet to establish themselves in the field of corrosion science. These techniques are capable of revealing surface structure to atomic resolution, and are totally undamaging to the surface. They can be used in principle in any environment in situ, even under polarization within an electrolyte. Their application to date has been chiefly to clean metal surfaces and surfaces carrying single monolayers of adsorbed material, rendering examination of the adsorption of inhibitors possible. They will indubitably find use in passive film analysis. 

This introductory book, moderate in size and sophistication, is not intended to be the ultimate STM treatise. The first part of this book, especially, is not intended to be a comprehensive review of all published STM theories. More sophisticated theoretical approaches, such as those directly based on first-principle numerical calculations, are beyond the scope of this introductory book. With its moderate scope, this book is also not intended to cover all applications of STM. Rather, the applications presented are illustrative in nature. Several excellent collections of review articles on STM applications have already been published or are in preparation. An exhaustive presentation of STM applications to various fields of science and technology needs a book series, with at least one additional volume per year. Moreover, this book does not cover the numerous ramifications of STM, except a brief chapter on AFM. The references listed at the back of the book do not represent a catalog of existing STM literature. Rather, it is a list of references that would have lasting value for the understanding of the fundamental physics in STM and AFM. Many references from related fields, essential to the understanding of the fundamental processes in STM and AFM, are also included. 

Successful syntheses of a wide variety of zeolite and zeotype materials have been developed over the last 50 years. Much is known about the way in which these structures are formed, particularly from recent detailed studies using advanced techniques of microscopy (HRTEM and AFM). However, a number of issues surrounding the mechanism of synthesis remain incompletely resolved. This is partly due to experimental difficulty but is also a reflection of the fact that not all systems arc the same. Nevertheless, in the foregoing account an attempt has been made to review our existing knowledge in terms of basic similarities between one reaction regime and another. In this way, it is hoped to establish some overall principles which, with appropriate modification, may be found to be generally applicable, or at least to provide a framework for further analysis. 

AFM (atomic force microscopy) was developed about five years after STM (see Atomic force microscopy). It relies upon the measurement of the force of interaction between a sharp tip and a sample. Being based upon the measurement of force rather than current, it is applicable in principle to any material. The technique has great versatility, and as in the case of STM, imaging may be carried out under ambient or fluid conditions. The tip is attached to a flexible cantilever, which is rastered across a sample surface. As the interaction force between the tip and the sample changes, the deflection of the cantilever varies. The cantilever deflection is readily measured (by optical deflection in most commercial systems) and is proportional to the interaction force leading to quantification, provided the spring constant of the lever is known. Either the cantilever or the sample is mounted on a piezoelectric crystal in order to exact fine control over the relative movements of the tip. 

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