Editing Atomic force microscopy (section)

==Advantages and disadvantages==
[[File:Atomic Force Microscope Science Museum London.jpg|thumb|The first atomic force microscope]]

===Advantages===
AFM has several advantages over the [[scanning electron microscope]] (SEM).  Unlike the electron microscope, which provides a two-dimensional projection or a two-dimensional image of a sample, the AFM provides a three-dimensional surface profile.  In addition, samples viewed by AFM do not require any special treatments (such as metal/carbon coatings) that would irreversibly change or damage the sample, and does not typically suffer from charging artifacts in the final image.  While an electron microscope needs an expensive [[vacuum]] environment for proper operation, most AFM modes can work perfectly well in ambient air or even a liquid environment.  This makes it possible to study biological macromolecules and even living organisms.  In principle, AFM can provide higher resolution than SEM.  It has been shown to give true atomic resolution in ultra-high vacuum (UHV) and, more recently, in liquid environments. High resolution AFM is comparable in resolution to [[scanning tunneling microscopy]] and [[transmission electron microscopy]]. AFM can also be combined with a variety of optical microscopy and spectroscopy techniques such as fluorescent microscopy of infrared spectroscopy, giving rise to [[Near-field scanning optical microscope|scanning near-field optical microscopy]], [[nano-FTIR]] and further expanding its applicability. Combined AFM-optical instruments have been applied primarily in the biological sciences but have recently attracted strong interest in photovoltaics<ref name="Geisse 2009 40–45"/> and energy-storage research,<ref>{{Cite journal|last1=Ayache |first1=Maurice|last2=Lux|first2=Simon Franz|last3=Kostecki|first3=Robert |date=2015-04-02|title=IR Near-Field Study of the Solid Electrolyte Interphase on a Tin Electrode |journal=The Journal of Physical Chemistry Letters |volume=6|issue=7|pages=1126–1129|pmid=26262960 |doi=10.1021/acs.jpclett.5b00263|issn=1948-7185}}</ref> polymer sciences,<ref>{{Cite journal|last1=Pollard |first1=Benjamin|last2=Raschke|first2=Markus B.|date=2016-04-22 |title=Correlative infrared nanospectroscopic and nanomechanical imaging of block copolymer microdomains|journal=Beilstein Journal of Nanotechnology|language=en|volume=7|issue=1|pages=605–612|doi=10.3762/bjnano.7.53|issn=2190-4286 |pmc=4901903|pmid=27335750}}</ref> nanotechnology<ref>{{Cite journal|last1=Huth|first1=F.|last2=Schnell |first2=M.|last3=Wittborn|first3=J.|last4=Ocelic|first4=N.|last5=Hillenbrand|first5=R.|title=Infrared-spectroscopic nanoimaging with a thermal source|journal=Nature Materials|volume=10|issue=5|pages=352–356 |doi=10.1038/nmat3006|pmid=21499314|bibcode=2011NatMa..10..352H|year=2011}}</ref><ref>{{Cite journal |last1=Bechtel|first1=Hans A.|last2=Muller |first2=Eric A.|last3=Olmon|first3=Robert L.|last4=Martin |first4=Michael C.|last5=Raschke|first5=Markus B.|date=2014-05-20|title=Ultrabroadband infrared nanospectroscopic imaging|journal=Proceedings of the National Academy of Sciences|language=en|volume=111 |issue=20|pages=7191–7196|doi=10.1073/pnas.1400502111|issn=0027-8424|pmc=4034206|pmid=24803431 |bibcode=2014PNAS..111.7191B |doi-access=free}}</ref> and even medical research.<ref>{{Cite journal |vauthors=Paluszkiewicz C, Piergies N, Chaniecki P, Rękas M, Miszczyk J, Kwiatek WM |date=2017-05-30 |title=Differentiation of protein secondary structure in clear and opaque human lenses: AFM – IR studies |journal=Journal of Pharmaceutical and Biomedical Analysis|volume=139|pages=125–132 |doi=10.1016/j.jpba.2017.03.001|pmid=28279927|s2cid=21232169}}</ref>

===Disadvantages===
A disadvantage of AFM compared with the [[scanning electron microscope]] (SEM) is the single scan image size. In one pass, the SEM can image an area on the order of square [[millimeter]]s with a [[depth of field]] on the order of millimeters, whereas the AFM can only image a maximum scanning area of about 150×150 micrometers and a maximum height on the order of 10–20 micrometers. One method of improving the scanned area size for AFM is by using parallel probes in a fashion similar to that of [[Millipede memory|millipede data storage]].

The scanning speed of an AFM is also a limitation. Traditionally, an AFM cannot scan images as fast as an SEM, requiring several minutes for a typical scan, while an SEM is capable of scanning at near real-time, although at relatively low quality. The relatively slow rate of scanning during AFM imaging often leads to thermal drift in the image<ref name="feature2004">{{cite journal|author=R. V. Lapshin|year=2004 |title=Feature-oriented scanning methodology for probe microscopy and nanotechnology |journal=Nanotechnology|volume=15|issue=9|pages=1135–1151|issn=0957-4484|doi=10.1088/0957-4484/15/9/006 |url=http://www.lapshin.fast-page.org/publications.htm#feature2004 |format=PDF|bibcode=2004Nanot..15.1135L |s2cid=250913438 |url-access=subscription}}</ref><ref name="automatic2007">{{cite journal|author=R. V. Lapshin|year=2007 |title=Automatic drift elimination in probe microscope images based on techniques of counter-scanning and topography feature recognition|journal=[[Measurement Science and Technology]]|volume=18|issue=3|pages=907–927 |issn=0957-0233|doi=10.1088/0957-0233/18/3/046|bibcode=2007MeScT..18..907L |s2cid=121988564 |url=http://www.lapshin.fast-page.org/publications.htm#automatic2007|format=PDF|url-access=subscription}}</ref><ref name="scanning1994">{{cite journal|author1=V. Y. Yurov|author2=A. N. Klimov|year=1994|title=Scanning tunneling microscope calibration and reconstruction of real image: Drift and slope elimination |journal=Review of Scientific Instruments|volume=65|issue=5|pages=1551–1557|issn=0034-6748 |doi=10.1063/1.1144890|url-status=dead |url=http://rsi.aip.org/resource/1/rsinak/v65/i5/p1551_s1|archive-url=https://archive.today/20120713061116/http://rsi.aip.org/resource/1/rsinak/v65/i5/p1551_s1|archive-date=2012-07-13|format=PDF |bibcode=1994RScI...65.1551Y|url-access=subscription}}</ref> making the AFM less suited for measuring accurate distances between topographical features on the image. However, several fast-acting designs<ref>{{cite journal|author1=G. Schitter |author2=M. J. Rost |year=2008 |title=Scanning probe microscopy at video-rate |journal=Materials Today |volume=11 |issue=special issue |pages=40–48 |issn=1369-7021 |doi=10.1016/S1369-7021(09)70006-9 |doi-access=free }}</ref><ref>{{cite journal|author1=R. V. Lapshin |author2=O. V. Obyedkov |year=1993|title=Fast-acting piezoactuator and digital feedback loop for scanning tunneling microscopes|journal=Review of Scientific Instruments|volume=64|issue=10|pages=2883–2887|issn=0034-6748|doi=10.1063/1.1144377|url=http://www.lapshin.fast-page.org/publications.htm#fast1993|format=PDF |bibcode=1993RScI...64.2883L|url-access=subscription}}</ref> were suggested to increase microscope scanning productivity including what is being termed videoAFM (reasonable quality images are being obtained with videoAFM at video rate: faster than the average SEM). To eliminate image distortions induced by thermal drift, several methods have been introduced.<ref name="feature2004"/><ref name="automatic2007"/><ref name="scanning1994"/>
[[File:Afm artifact2.png|thumb|Showing an AFM artifact arising from a tip with a high radius of curvature with respect to the feature that is to be visualized]]
[[File:Afm artifact.svg|thumb|AFM artifact, steep sample topography]]

AFM images can also be affected by nonlinearity, [[hysteresis]],<ref name="analytical1995">{{cite journal|author=R. V. Lapshin|year=1995|title=Analytical model for the approximation of hysteresis loop and its application to the scanning tunneling microscope|journal=Review of Scientific Instruments | volume=66|issue=9|pages=4718–4730|issn=0034-6748|doi=10.1063/1.1145314|url=http://www.lapshin.fast-page.org/publications.htm#analytical1995|format=PDF|bibcode = 1995RScI...66.4718L |arxiv=2006.02784|s2cid=121671951}} ([http://www.lapshin.fast-page.org/publications.htm#analytical1995 Russian translation] is available).</ref> and [[Creep (deformation)|creep]] of the piezoelectric material and cross-talk between the ''x'', ''y'', ''z'' axes that may require software enhancement and filtering. Such filtering could "flatten" out real topographical features. However, newer AFMs utilize real-time correction software (for example, [[feature-oriented scanning]]<ref name="fospm2011">{{cite book|author=R. V. Lapshin|year=2011|contribution=Feature-oriented scanning probe microscopy|title=Encyclopedia of Nanoscience and Nanotechnology|editor=H. S. Nalwa|volume=14|pages=105–115|publisher=American Scientific Publishers|location=USA|isbn=978-1-58883-163-7|url=http://www.lapshin.fast-page.org/publications.htm#fospm2011|format=PDF}}</ref><ref name="feature2004"/>) or closed-loop scanners, which practically eliminate these problems. Some AFMs also use separated orthogonal scanners (as opposed to a single tube), which also serve to eliminate part of the cross-talk problems.

As with any other imaging technique, there is the possibility of [[image artifacts]], which could be induced by an unsuitable tip, a poor operating environment, or even by the sample itself, as depicted on the right. These image artifacts are unavoidable; however, their occurrence and effect on results can be reduced through various methods.
Artifacts resulting from a too-coarse tip can be caused for example by inappropriate handling or de facto collisions with the sample by either scanning too fast or having an unreasonably rough surface, causing actual wearing of the tip.

Due to the nature of AFM probes, they cannot normally measure steep walls or overhangs.  Specially made cantilevers and AFMs can be used to modulate the probe sideways as well as up and down (as with dynamic contact and non-contact modes) to measure sidewalls, at the cost of more expensive cantilevers, lower lateral resolution and additional artifacts.