Scanning tunneling microscopy probe position

The ability to control the position of a fine tip in order to scan surfaces with subatomic resolution has brought scanning probe microscopies to the forefront in surface imaging techniques. We discuss the two primary techniques, scanning tunneling microscopy (STM) and atomic force microscopy (AFM) the interested reader is referred to comprehensive reviews [9, 17, 18]. 

Scanning tunnelling microscopy (STM) [33, 34] is widely used for investigations of the local atomic structure of surfaces. A probe "tip" is scanned across the surface revealing the positions of individual atoms. With its ability to achieve atomic resolution and, in most cases, distinguish between chemical species, the STM has provided key insights into the nature of alloy formation on surfaces. Both the static and dynamic properties of surface alloys can be probed with the STM. For the system of Pb on Cu, STM measurements were first to show the existence of surface alloy phases unambiguously and identify many of their stmctural properties [20-22, 35]. 

Since the inception of scanning tunneling microscopy (STM), electrochemists have sought to take advantage of scanned probe microscopy (SPM) techniques to manipulate the spatial position of an electrode with high resolution. In addition to STM,... 

Due to such advantages as high resolution that can approach the real atomic and molecular scale, and the ability to perform real-time measurement that cannot be matched by traditional microscopy, scanning tunneling microscopy (STM) and atomic force microscopy (AFM) have attracted considerable attention since their introduction from researchers in various fields. The operational procedure of these microscopes is to position an atomically sharp detector needle to less than several nanometers from the surface of a sample, probe the interaction between the detector needle and the sample, scan the sample surface two-dimensionally, and obtain the surface image (an unprecedented method). If the interaction that is probed is the tunneling of the electron that is well known in quantum mechanics, the technique is called STM (T indicates tunneling). If, on the other hand, atomic force (van der Waals force) is used, it is called AFM. 

Quantum mechanics describes and defines the behavior of electrons in atoms. One of the rules of quantum behavior is that electrons are constrained to specific locales known as orbitals within the structure of an atom and are not allowed to exist at the boundaries of those locales. An observable property called quantum mechanical tunneling occurs, however, which permits electrons to move from one locale to another across the orbital boundaries. In scanning probe microscopy the miniscule electrical current due to quantum mechanical tunneling between the atoms at a surface and the atoms at the tip of an atomic-scale probe is measured as a function of their relative positions. This provides a corresponding atomic scale map of the surface structure. 

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