Force microscope

Fig. VIII-1. Schematic illustration of the scanning tunneling microscope (STM) and atomic force microscope (AFM). (From Ref. 9.)...

Fig. Vni-3. (a) Atomic force microscope (AFM) and (b) transmission electron microscope (TEM) images of lead selenide particles grown under arachidic acid monolayers. (Pi Ref. 57.)...

There are many other experiments in which surface atoms have been purposely moved, removed or chemically modified with a scanning probe tip. For example, atoms on a surface have been induced to move via interaction with the large electric field associated with an STM tip [78]. A scaiming force microscope has been used to create three-dimensional nanostructures by pushing adsorbed particles with the tip [79]. In addition, the electrons that are tunnelling from an STM tip to the sample can be used as sources of electrons for stimulated desorption [80]. The tuimelling electrons have also been used to promote dissociation of adsorbed O2 molecules on metal or semiconductor surfaces [81, 82]. 

Detection of cantilever displacement is another important issue in force microscope design. The first AFM instrument used an STM to monitor the movement of the cantilever—an extremely sensitive method. STM detection suffers from the disadvantage, however, that tip or cantilever contamination can affect the instrument s sensitivity, and that the topography of the cantilever may be incorporated into the data. The most coimnon methods in use today are optical, and are based either on the deflection of a laser beam [80], which has been bounced off the rear of the cantilever onto a position-sensitive detector (figme B 1.19.18), or on an interferometric principle [81]. 

Figure Bl.19.18. Schematic of an atomic force microscope showing the optical lever principle.

The technological importance of thin films in snch areas as semicondnctor devices and sensors has led to a demand for mechanical property infonnation for these systems. Measuring the elastic modnlns for thin films is mnch harder than the corresponding measurement for bnlk samples, since the results obtained by traditional indentation methods are strongly perturbed by the properties of the substrate material. Additionally, the behaviour of the film under conditions of low load, which is necessary for the measnrement of thin-film properties, is strongly inflnenced by surface forces [75]. Since the force microscope is both sensitive to surface forces and has extremely high depth resolntion, it shows considerable promise as a teclnhqne for the mechanical characterization of thin films. 

Salmeron M B 1993 Use of the atomic force microscope to study mechanical properties of lubricant layers MRS Bulletin XVIII-5 20... 

Binnig G, Quate C F and Gerber Ch 1986 Atomic force microscope Phys. Rev. Lett. 56 930... 

Carpick R W, Agrait N, Ogletree D F and Salmeron M 1996 Measurement of interfacial shear (friction) with an ultrahigh vacuum atomic force microscope J. Vac. Sc/. Technol. B 14 1289... 

Ducker W A, Senden T J and Pashley R M 1992 Measurement of forces in liquids using a force microscope Langmuir 8 1831... 

Thundat T, Zheng X-Y, Chen G Y, Sharp S L, Warmack R J and Schowalter L J 1993 Characterization of atomic force microscope tips by adhesion force measurements App/. Phys. Lett. 63 2150... 

Hansma H G, Vesenka J, Siegerist C, Kelderman G, Morrett H, Sinsheimer R L, Bustamante C, Elings V and Hansma P K 1992 Reproducible imaging and dissection of plasmid DNA under liquid with the atomic force microscope Science 256 1180... 

Jarvis S P, Yamamoto S-l, Yamada H, Tokumoto H and Pethica J B 1997 Tip-surface interactions studied using a force controlled atomic force microscope in ultrahigh vacuum Appl. Phys. Lett. 70 2238... 

Aibrecht T R, Grutter P, Florne D and Rugar D 1991 Frequency moduiation detection using high-Q cantiievers for enhanced force microscope sensitivity J. Appl. Phys. 69 668... 

Meyer G and Amer N M 1990 Simultaneous measurement of lateral and normal forces with an optical-beam-deflection atomic force microscope Appl. Phys. Lett. 57 2089... 

Kolosov O and Yamanaka K 1993 Nonlinear detection of ultrasonic vibrations in an atomic force microscope Japan. J. Appl. Phys. 32 LI 095... 

Friedbacher G, Hansma P K, Ramil E and Stucky G D 1991 Imaging powders with the atomic force microscope from biominerals to commercial materials Sc/e/ ce 253 1261... 

Keita B, Nad]o L and K]oller K 1991 Surface characterization of a single crystal of sodium decatungstocerate (IV) by the atomic force microscope Surf. Sc/. Lett. 256 L613... 

Overney R, Howald L, Frommer J, Meyer E and Guntherodt H 1991 Molecular surface structure of tetracene mapped by the atomic force microscope J. Chem. Phys. 94 8441... 

Radmacher M, Fritz M, Hansma H G and Hansma P K 1994 Direct observation of enzyme activity with the atomic force microscope Science 265 1577... 

Muller D W, Fotiadis D and Engel A 1998 Mapping flexible protein domains at subnanometre resolution with the atomic force microscope FEBS Lett. 430 105... 

Li Y Q, Tao N J, Pan J, Garcia A A and Lindsay S M 1993 Direct measurement of interaction forces between colloidal particles using the scanning force microscope Langmuir 9 637... 

Overney R M, Meyer E, Frommer J, Brodbeck D, Luthi R, Flowald L, Guntherodt Fl-J, Fu]ihara M, Takano FI and Gotoh Y 1992 Friction measurements of phase separated thin films with a modified atomic force microscope Nature... 

Manne S, Flansma P K, Massie J, Elings V B and Gewirth A A 1991 Atomic-resolution electrochemistry with the atomic force microscope copper deposition on gold Science 251 183... 

Jarvis S P and Tokumoto FI 1997 Measurement and interpretation of forces in the atomic force microscope Probe Microscopy 1 65... 

It is remarkable that tire roots of the SFA go back to the early 1960s [1], Tabor and Winterton [2] and Israelachvili and Tabor [3] developed it to the current state of the art some 15 years before the invention of the more widely used atomic force microscope (AFM) (see chapter B1.19). 

Cleveland J P, Schaffer T E and Hansma P K 1995 Probing oscillatory hydration potentials using thermal-mechanical noise in an atomic force microscope Rhys. Rev. B 52 R8692-5... 

Fisher T E, Oberhauser A F, Carrion-Vazquez M, Marszalek P E and Fernandez J M 1999 The study of protein mechanics with the atomic force microscope Trends Biochem. Sci. 24 379-84... 

Surfaces can be characterized using scaiming probe microscopies (see section B1.19). In addition, by attaching a colloidal particle to tire tip of an atomic force microscope, colloidal interactions can be probed as well [27]. Interactions between surfaces can be studied using tire surface force apparatus (see section B1.20). This also helps one to understand tire interactions between colloidal particles. 

The atomic force microscope (ATM) provides one approach to the measurement of friction in well defined systems. The ATM allows measurement of friction between a surface and a tip with a radius of the order of 5-10 nm figure C2.9.3 a)). It is the tme realization of a single asperity contact with a flat surface which, in its ultimate fonn, would measure friction between a single atom and a surface. The ATM allows friction measurements on surfaces that are well defined in tenns of both composition and stmcture. It is limited by the fact that the characteristics of the tip itself are often poorly understood. It is very difficult to detennine the radius, stmcture and composition of the tip however, these limitations are being resolved. The AFM has already allowed the spatial resolution of friction forces that exlribit atomic periodicity and chemical specificity [3, K), 13]. 

Figure C2.9.3 Schematic diagrams of the interfaces reaiized by (a) tire atomic force microscope, (b) tire surface forces apparatus and (c) tire quartz crystai microbaiance for achieving fundamentai measurements of friction in weii defined systems.

Chen C-FI, Washburn N and Gewirth A A 1993 In situ atomic force microscope study of Pb underpotential deposition on Au(111) Structural properties of the catalytically active phase J.Phys. Chem. 97 9754-60... 

Microscopic Interpretation of Atomic Force Microscope Rupture Experiments... 

That simulation study [49] aimed at a microscopic interpretation of single molecule atomic force microscope (AFM) experiments [50], in which unbinding forces between individual protein-ligand complexes have been m( asured... 

Fig. 5. Block diagram of contact atomic force microscope system in which cantilever deflection monitored optically with position-sensitive photodiode...

Newer techniques that are responding to the need for atomic level imaging and chemical analysis include scanning tunneling microscopes (STMs), atomic force microscopes (AFMs) (52), and focused ion beams (FIBs). These are expected to quickly pass from laboratory-scale use to in-line monitoring apphcations for 200-mm wafers (32). 

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