AFM probe
Encyclopedia
Consumable and measuring device with a sharp tip on the free swinging end of a cantilever
which is protruding from a holder plate used in Atomic force microscopes (AFM). The dimensions of the cantilever
are in the scale of micrometers. The radius of the tip is in the scale of a few nanometers. The holder plate, also called holder chip, - often 1.6 mm by 3.4 mm in size - allows the operator to hold the AFM probe with tweezers and fit it into the corresponding holder clips on the scanning head of the Atomic force microscope.
is deflected. The deflection is a function of the interaction between the tip and the surface and the Atomic force microscope has a function to measure this deflection. If the deflection is measured at many points of a 2D surface, this interaction can be mapped spatially.
The surface of the cantilevers can also be modified. These coatings are mostly applied in order to increase the reflectance of the cantilever and to improve the deflection signal.
. Most AFM probes used are made from silicon
(Si). Borosilicate glass
, silicon nitride
are other materials in use.
" - employing the name of a single part as the name of the whole device. "AFM probes" are part of the "Scanning probe microscopy
" or "SPM
" probes.
Cantilever
A cantilever is a beam anchored at only one end. The beam carries the load to the support where it is resisted by moment and shear stress. Cantilever construction allows for overhanging structures without external bracing. Cantilevers can also be constructed with trusses or slabs.This is in...
which is protruding from a holder plate used in Atomic force microscopes (AFM). The dimensions of the cantilever
Cantilever
A cantilever is a beam anchored at only one end. The beam carries the load to the support where it is resisted by moment and shear stress. Cantilever construction allows for overhanging structures without external bracing. Cantilevers can also be constructed with trusses or slabs.This is in...
are in the scale of micrometers. The radius of the tip is in the scale of a few nanometers. The holder plate, also called holder chip, - often 1.6 mm by 3.4 mm in size - allows the operator to hold the AFM probe with tweezers and fit it into the corresponding holder clips on the scanning head of the Atomic force microscope.
How it works
As the tip is approached very closely to the surface of the investigated object, the cantileverCantilever
A cantilever is a beam anchored at only one end. The beam carries the load to the support where it is resisted by moment and shear stress. Cantilever construction allows for overhanging structures without external bracing. Cantilevers can also be constructed with trusses or slabs.This is in...
is deflected. The deflection is a function of the interaction between the tip and the surface and the Atomic force microscope has a function to measure this deflection. If the deflection is measured at many points of a 2D surface, this interaction can be mapped spatially.
Use
Several types of interaction can be detected. Depending on the interaction under investigation, the surface of the tip of the AFM probe needs to be modified with a coating. Among the coatings used are gold - for covalent bonding of biological molecules and the detection of their interaction with a surface, diamond for increased wear resistance and magnetic coatings for detecting the magnetic properties of the investigated surface.The surface of the cantilevers can also be modified. These coatings are mostly applied in order to increase the reflectance of the cantilever and to improve the deflection signal.
Fabrication
AFM probes are manufactured with MEMS technologyMicroelectromechanical systems
Microelectromechanical systems is the technology of very small mechanical devices driven by electricity; it merges at the nano-scale into nanoelectromechanical systems and nanotechnology...
. Most AFM probes used are made from silicon
Silicon
Silicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table...
(Si). Borosilicate glass
Borosilicate glass
Borosilicate glass is a type of glass with the main glass-forming constituents silica and boron oxide. Borosilicate glasses are known for having very low coefficients of thermal expansion , making them resistant to thermal shock, more so than any other common glass...
, silicon nitride
Silicon nitride
Silicon nitride is a chemical compound of silicon and nitrogen. If powdered silicon is heated between 1300° and 1400°C in an atmosphere of nitrogen, trisilicon tetranitride, Si3N4, is formed. The silicon sample weight increases progressively due to the chemical combination of silicon and nitrogen...
are other materials in use.
Naming
"AFM probe" is the most popular name in use for this device. Other names include "AFM tip" and "cantileverCantilever
A cantilever is a beam anchored at only one end. The beam carries the load to the support where it is resisted by moment and shear stress. Cantilever construction allows for overhanging structures without external bracing. Cantilevers can also be constructed with trusses or slabs.This is in...
" - employing the name of a single part as the name of the whole device. "AFM probes" are part of the "Scanning probe microscopy
Scanning probe microscopy
Scanning Probe Microscopy is a branch of microscopy that forms images of surfaces using a physical probe that scans the specimen. An image of the surface is obtained by mechanically moving the probe in a raster scan of the specimen, line by line, and recording the probe-surface interaction as a...
" or "SPM
Scanning probe microscopy
Scanning Probe Microscopy is a branch of microscopy that forms images of surfaces using a physical probe that scans the specimen. An image of the surface is obtained by mechanically moving the probe in a raster scan of the specimen, line by line, and recording the probe-surface interaction as a...
" probes.