This section provides overview, applications, and principles of atomic force microscopes. Also, please take a look at the list of 10 atomic force microscope manufacturers and their company rankings.
AFM's (Atomic Force Microscopes) are a microscope that visualizes the fine surface structure of a sample by detecting and scanning the force acting between a probe called a cantilever and atoms on the sample surface.
Scanning tunneling microscopes have a longer history in microscopy for visualizing surface microstructures, but these microscopes are limited to the measurement of conductive samples because they generate a tunneling current between the cantilever and the sample. The AFM is characterized by its ability to measure a wide range of objects, from conductive samples to insulators and biological samples.
AFM is mainly used in the industrial field for inspection purposes because it can reveal surface irregularities at the nanoscale (1 nm = 10-9 m) to angstrom (0.1 nm) level.
For example, it is used to measure the uniformity and roughness of the surface treatment of semiconductor substrates and to inspect the corrosion and degradation of plating on electrodes made of metals such as gold and copper. In research applications, it is also used to minimally invasively observe reactions and structural changes in proteins and other biomolecules.
The name of this mode varies from manufacturer to manufacturer, but it is the mode in which the cantilever is made to vibrate near its resonant frequency. When the tip of the cantilever approaches the sample, the amplitude changes. This mode uses this phenomenon to keep the amplitude constant and acquire the displacement in the direction of the sample height.
AFM's measure the displacement of a cantilever by the atomic force acting between the cantilever and the sample surface. The most common method of displacement detection is to use a photodiode to detect the displacement of the cantilever.
The reflected light is monitored by irradiating light onto the plane behind the cantilever, and when the cantilever is attracted to the sample surface by the interatomic force, the angle of the reflected light changes, which is detected and feedback is applied to correct the angle of the cantilever again. The control pattern at this time is visualized as the shape of the surface irregularity. This detection method is called the optical leverage method.
The other method is to vibrate the cantilever up and down using a piezoelectric element and monitor the amplitude, phase, and frequency of the vibration. The measurement is performed by scanning the cantilever with feedback so that the amplitude, phase, and frequency are constant.
Another method is to directly measure the force applied to the cantilever by measuring its flexure. In this case, the AFM is used to measure the localization of membrane proteins and the mechanical properties of cells, rather than to measure surface topography.
Forces that can be detected using AFM's include forces of attraction, repulsion, adhesion between the terminal tip and the surface of the material, and binding forces. The AFM is also used in the field of catalysis. Examples of applications are listed below.
They are used in the mic observation of single crystal zeolites and layered clay minerals. Mica cleavage surfaces, which are atomically smooth, can be used to observe palladium particles as small as a few nm on palladium catalysts deposited on the mica cleavage surfaces. In addition to not requiring any special pretreatment of materials for measurement, the AFM is characterized by its ability to perform measurements in a wide range of environments, including in air and liquids. This feature is used as a means of measuring adsorption phenomena and chemical reaction processes in localized surface areas. An example of such a measurement is the adsorption process of a soft organic compound. By modifying the tip, forces other than atomic forces can be selectively measured. As an example, the tip can be chemically modified with an organic monolayer to function as a chemical sensor.
Force curves are utilized to measure interaction forces. The force curve is measured by moving the tip back and forth in a reciprocating motion, repeatedly contacting and pulling the material and the tip apart. This reciprocating motion measures the force curve as a function of the force and distance between the tip and the material surface.
The force curve may not track the original force curve due to cantilever instability, causing the actual force curve to be distorted. To avoid this problem, the appropriate cantilever must be selected for the force orientation.
Force curve measurements in air measure van der Waals forces as well as surface tension-based adhesion and meniscus forces from contact to pull apart. In some cases, force curve measurements have been applied to the evaluation of acid-base behavior of solid surfaces.
An STM has high atomic resolution in ultra-high vacuum, but is strongly affected by non-conductive materials and surface contamination that occurs in air. AFM detects the force between the material and the tip, so it can measure non-conductive materials and can also measure in air.
*Including some distributors, etc.
Sort by Features
Sort by Area
This is the version of our website addressed to speakers of English in the United States. If you are a resident of another country, please select the appropriate version of Metoree for your country in the drop-down menu.