Conductive-probe atomic force microscope

There are of course many other similarities and differences, and some of them are listed in Table 5.1 without further explanations. In general, STM is very versatile and flexible. Especially with the development of the atomic force microscope (AFM), materials of poor electrical conductivity can also be imaged. There is the potential of many important applications. A critically important factor in STM and AFM is the characterization of the probing tip, which can of course be done with the FIM. FIM, with its ability to field evaporate surface atoms and surface layers one by one, and the capability of single atom chemical analysis with the atom-probe FIM (APFIM), also finds many applications, especially in chemical analysis of materials on a sub-nanometer scale. It should be possible to develop an STM-FIM-APFIM system where the sample to be scanned in STM is itself an FIM tip so that the sample can either be thermally treated or be field evaporated to reach into the bulk or to reach to an interface inside the sample. After the emitter surface is scanned for its atomic structure, it can be mass analyzed in the atom-probe for one atomic layer,... 

The next radical improvement in scanned probe microscopies was the invention of the atomic force microscope (AFM) in 1986 by Binnig, Quate,92 and Gerber93 [29]. The X- and Y-piezoelectric scanners were kept, but the atomically sharp conducting tip was replaced by a sharp (but not atomically sharp ) Si cantilever (Fig. 11.42), with a mirror glued to its back. 

While the previously described techniques both require extrapolation of measured data in order to calculate the contact resistance, Kelvin probe force microscopy (KFM, also known as scanning surface potential microscopy or scanning potenti-ometry) can be used to determine the source and drain contributions to the contact resistance directly. In KFM, a conductive atomic force microscope (AFM) tip is scanned over the operational OFET channel twice. On the first pass, the topography... 

For the analysis of bioerodible polymers, the atomic force microscope (AFM) is more suited than the STM because its imaging mechanism is independent of electron conduction and hence insulating organic materials can be directly visualized (Burnham and Colton, 1993). The basic components of an AFM are shown in Figure 7. The sample is mounted onto a piezoceramic scanner device capable of moving the sample in all three-dimensions. Above the sample surface is the AFM probe unit, which is composed of a sharp probe positioned on the end of a flexible cantilever. The cantilever is microfabricated in a V-shape with the two arms of the V attached to a stationary support. 

Atomic force microscopes (AFM), whose tips are typically made of silicon or diamond, can probe sur-laces made of practically any material. As the tip of an atomic force microscope is dragged across the sur-lace of a specimen, it is either deflected by or drawn toward the object, depending on whether the atoms in the object are repelled by or attracted to the microscope s tip. By measuring these forces, a magnified representation of the physical structure of the sample can be created. By changing the modes in which these microscopes operate, different properties such as magnetism, friction, and electrical conductivity can be assessed. 

There are two primary types of scanning probe instrument, the scarming tunneling microscope (STM) and the atomic force microscope (AFM). Surface examination by STM relies on electrical conductivity between the surface and the probe therefore only electrically conductive samples can be examined. The AFM relies on the force interaction between the probe arrd srrrface allowing a much wider variety of samples to be studied. We have chosen to exarrrine the AFM in more detail due to the broad rratrrre of the techrrique. 

A number of conjugated 2D pol3mers are electrically conducting and offer promise for application in molecular electronics, a field that pushes the goal of miniaturization to the ultimate extreme. Self-assembled monolayers (SAMs) can be assembled on a gold electrode and the other end of the molecular wire probed with a Au tip of a conductive atomic force microscope (CAFM) for the conductivity measurement. An organometallic example is shown in Fig. 13.8, where conductivity is much enhanced by the presence of the redox-active ferrocene units. ... 

Ultrahard fullerites with disordered structure and hardness of more than 200 GPa are already used as material for heavy-duty probes of scanning atomic force microscopes-nanoindenters. In combination with electrically conducting properties it enables one to investigate not only the mechanical properties of solid bodies by the AFM method, but also the electrical properties. Application of an ultrahard fullerite as an indentor material has allowed one to measure correctly for the first time the hardness of diamond at room temperature. 

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