Editing Atomic force microscopy (section)

==Probe==
An AFM probe has a sharp tip on the free-swinging end of a cantilever that protrudes from a holder.<ref>Bryant, P. J.;   Miller, R. G.;   Yang, R.; "Scanning tunneling and atomic force microscopy combined". ''[[Applied Physics Letters]]'', Jun 1988, Vol: 52 Issue:26, p. 2233–2235, {{ISSN|0003-6951}}.</ref> The dimensions of the cantilever are in the scale of micrometers. The radius of the tip is usually on the scale of a few nanometers to a few tens of nanometers. (Specialized probes exist with much larger end radii, for example probes for indentation of soft materials.) The  cantilever holder, also called the holder chip—often 1.6&nbsp;mm by 3.4&nbsp;mm in size—allows the operator to hold the AFM cantilever/probe assembly with tweezers and fit it into the corresponding holder clips on the scanning head of the atomic force microscope.

This device is most commonly called an "AFM probe", but other names include "AFM tip" and "cantilever" (employing the name of a single part as the name of the whole device). An AFM probe is a particular type of SPM probe.

AFM probes are manufactured with [[Microelectromechanical systems|MEMS technology]]. Most AFM probes used are made from [[silicon]] (Si), but [[borosilicate glass]] and [[silicon nitride]] are also in use. AFM probes are considered consumables as they are often replaced when the tip apex becomes dull or contaminated or when the cantilever is broken.  They can cost from a couple of tens of dollars up to hundreds of dollars per cantilever for the most specialized cantilever/probe combinations.

To use the device, the tip is brought very close to the surface of the object under investigation, and the cantilever is deflected by the interaction between the tip and the surface, which is what the AFM is designed to measure. A spatial map of the interaction can be made by measuring the deflection at many points on a 2D surface.

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,<ref>Oscar H. Willemsen, Margot M.E. Snel, Alessandra Cambi, Jan Greve, Bart G. De Grooth and Carl G. Figdor "Biomolecular Interactions Measured by Atomic Force Microscopy" ''[[Biophysical Journal]]'', Volume 79, Issue 6, December 2000, Pages 3267–3281.</ref> [[diamond]] for increased wear resistance<ref>Koo-Hyun Chung  and Dae-Eun Kim, "Wear characteristics of diamond-coated atomic force microscope probe". ''[[Ultramicroscopy]]'', Volume 108, Issue 1, December 2007, Pages 1–10</ref> and magnetic coatings for detecting the magnetic properties of the investigated surface.<ref>{{cite journal | last1 = Xu | first1 = Xin | last2 = Raman | first2 = Arvind | year = 2007 | title = Comparative dynamics of magnetically, acoustically, and Brownian motion driven microcantilevers in liquids | journal = [[J. Appl. Phys.]] | volume = 102 | issue = 1| pages = 014303–014303–7 |bibcode = 2007JAP...102a4303Y |doi = 10.1063/1.2751415 }}</ref> Another solution exists to achieve high resolution magnetic imaging: equipping the probe with a [[SQUID|microSQUID]]. The AFM tips are fabricated using silicon micro machining and the precise positioning of the microSQUID loop is achieved using electron beam lithography.<ref>{{cite journal | last1 = Hasselbach | first1 = K. | last2 = Ladam | first2 = C. | year = 2008 | title = High resolution magnetic imaging : MicroSQUID Force Microscopy | journal = Journal of Physics: Conference Series | volume = 97 | issue = 1| pages = 012330|bibcode =  2008JPhCS..97a2330H|doi = 10.1088/1742-6596/97/1/012330 | doi-access = free }}</ref> The additional attachment of a quantum dot to the tip apex of a conductive probe enables surface potential imaging with high lateral resolution, [[scanning quantum dot microscopy]].<ref>{{Cite journal|last1=Wagner|first1=Christian|last2=Green|first2=Matthew F. B.|last3=Leinen|first3=Philipp|last4=Deilmann|first4=Thorsten|last5=Krüger|first5=Peter|last6=Rohlfing|first6=Michael|last7=Temirov|first7=Ruslan|last8=Tautz|first8=F. Stefan|date=2015-07-06|title=Scanning Quantum Dot Microscopy|journal=Physical Review Letters|language=en|volume=115|issue=2|pages=026101|doi=10.1103/PhysRevLett.115.026101|pmid=26207484|issn=0031-9007|bibcode=2015PhRvL.115b6101W|arxiv=1503.07738|s2cid=1720328}}</ref>

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.