Принципы нанометрологии (1027623), страница 48
Текст из файла (страница 48)
Imageintensities above (or below) this level are taken to correspond to areas ofthe particle being measured. This is demonstrated in Figure 7.8b, wherea threshold was applied to identify the particles. Simple analysis allows thearea and radius of the particle to be determined. In the case of non-sphericalparticles the diameter is determined by the fitting of an ellipsoid. A histogramof the sizes can then be easily determined (Figure 7.8c).Although the threshold method described above is a simple, well-definedand recognised method it does suffer from some significant drawbacks. Thefirst is setting the threshold level, which is difficult for poorly contrastingparticles (such as small polymer particles or inhomogeneous particles (seeFigure 7.9)).
The second, more important, drawback occurs when analysingagglomerated particles. With no significant intensity difference between theparticles a simple threshold is insufficient to distinguish between the particles and hence accurately determine size. It is usually recommended to usea watershed method.7.6 Other particle beam microscopy techniquesIn order to get high-resolution images from any scanning beam microscope one must be able to produce a sufficiently small probe, haveOther particle beam microscopy techniquesFIGURE 7.8 (a) TEM image of nominal 30 nm diameter gold nanoparticles; (b) using threshold to identify theindividual particles; (c) histogram of the measured diameters.a small interaction volume in the substrate and have an abundance ofinformation-rich particles to create the image.
A typical SEM meets allof these requirements, but other particles can be used as well. Recently,a focused ion beam (FIB) [63] has become more and more popular. Theconcept of FIB is similar to that of SEM; however, the electrons arereplaced by ions of much larger masses. As a consequence they can in205206C H A P T ER 7 : Scanning probe and particle beam microscopyFIGURE 7.9 TEM image of 150-nm-diameter latex particles.
This image highlights thedrawback to TEM size measurement using TEM or SEM. The first is that a white ‘halo’surrounds the particle. Should the halo area be included in the size measurement? If sothere will be a difficulty in determining the threshold level. The second is the particles areaggregated, again making sizing difficult.general induce damage to a specimen by sputtering. However, for eachincoming ion two to eight secondary electrons are generated. Thisabundance of secondary electrons allows for very-high-contrast imaging.In addition to secondary electrons, backscattered ions are also availablefor imaging.
These ions are not as abundant as secondary electrons, butdo provide unique contrast mechanisms that allow quantitativediscrimination between materials with sub-micrometre spatial resolution.An electron beam has a relatively large excitation volume in the substrate.This limits the resolution of an SEM regardless of the probe size.
A heliumion beam does not suffer from this effect, as the excitation volume is muchsmaller than that of the SEM. SEMs are typically run at or near theirsecondary electron unity crossover point to minimize charging of the sample.This implies that for each incoming electron, one secondary electron is madeavailable for imaging.
The situation with the helium ion beam is much morefavourable.The helium ion microscope [64] has several unique properties that, whencombined, allow for higher-resolution imaging than that available today withconventional SEMs. In addition to better resolution, the helium ion microscope and the FIB also provide unique contrast mechanisms in bothsecondary electron mode and backscattered modes that enable materialdiscrimination and identification.References7.7 References[1] Binnig G, Rohrer H, Gerber Ch, Weibel E 1982 Surface studies by scanningtunneling microscopy Phys. Rev.
Lett. 49 57–61[2] Meyer E, Hug H J, Bennewitz R 2003 Scanning probe microscopy: the lab ona tip (Springer)[3] Weisendanger R 1994 Scanning probe microscopy and spectroscopy:methods and applications (Cambridge University Press)[4] Courion D 2003 Near-field microscopy and near-field optics (ImperialCollege Press)[5] Binnig G, Rohrer H 1987 Scanning tunneling microscopy - from birth toadolescence Rev. Mod. Phys.
59 615–625[6] Binnig G, Quate C F, Gerber Ch 1986 Atomic force microscopy Phys. Rev.Lett. 56 930–933[7] Magonov S 2008 Atomic force microscopy (John Wiley & Sons)[8] Thayson J, Boisen A, Hansen O, Bouwstra S 2000 Atomic force microscopyprobe with piezoresistive read-out and a highly sensitive Wheatstone bridgearrangement Sens. Act. A: Phys.
83 47–53[9] Howard L, Stone J, Fu J 1979 Real-time displacement measurement witha Fabry-Pérot cavity and a diode laser Precision Engineering 25 321–335[10] Meyer G, Amer N M 1988 Novel optical approach to atomic force microscopy Appl. Phys. Lett. 53 1045–1047[11] Gittes F, Schmidt C F 1998 Thermal noise limitations on micromechanicalexperiments Euro.
Biophys. J. 27 75–81[12] Wilkening G, Koenders L 2005 Nanoscale calibration standards and methods(Wiley-VCH)[13] Mechler Á, Kopniczsky J, Kocavecz J, Hoel A, Granqvist C-G, Heszler P 2005Anomalies in nanostructure size measurements by AFM Phys. Rev. B 72125407[14] Dai G, Koenders L, Pohlenz F, Dziomba T, Danzebrink H-U 2005 Accurateand traceable calibration of one-dimensional gratings Meas. Sci. Technol. 161241–1249[15] Albrecht T R, Alkamine S, Carver T E, Quate C F 1990 Microfabrication ofcantilever styli for the atomic force microscope J. Vac.
Sci. Technol. A 8 3386–3396[16] Keller D 1993 Reconstruction of STM and AFM images distorted by finitesized tips Surf. Sci. 253 353–364[17] Villarubia J S 1994 Morphological estimation of tip geometry for scannedprobe microscopy Surf. Sci. 321 287–300[18] Bakucz P, Yacoot A, Dziomba T, Koenders L, Krüger-Sehm R 2008 Neuralnetwork approximation of tip-abrasion effects in AFM imaging Meas. Sci.Technol. 19 065101207208C H A P T ER 7 : Scanning probe and particle beam microscopy[19] van Cleef M, Holt S A, Watson G S, Myhra S 2003 Polystyrene spheres onmica substrate: AFM calibration, tip parameters and scan artefactsJ Microscopy 181 2–9[20] Hübner U, Morgenroth W, Meyer H G, Sultzbach T, Brendel B, Mirandé W2003 Downwards to metrology in nanoscale: determination of the AFM tipshape with well-known sharp edge calibration structures Appl.
Phys. A:Mater. Sci. Process. 76 913–817[21] Seah M P, Spencer S J, Cumpson P J, Johnstone J E 2000 Sputter-inducedcone and filament formation on InP and AFM tip shape determination Surf.Interf. Anal. 29 782–790[22] Lo Y-S, Huefner N D, Chan W S, Dryden P, Hagenhoff P, Beebe T P 1999Organic and inorganic contamination on commercial AFM cantileversLangmuir 15 6522–6526[23] Jorgensen J F, Jensen C P, Garnaes J 1998 Lateral metrology using scanningprobe microscopes, 2D pitch standards and image processing Appl.
Phys. A:Mater. Sci. Process. 66 S847–S852[24] Haycocks J A, Jackson K 2005 Traceable calibration of transfer standards forscanning probe microscopy Precision Engineering 29 168–175[25] Meli F, Thalmann R 1998 Long-range AFM profiler used for accurate pitchmeasurements Meas. Sci. Technol. 9 1087–1092[26] Dixson R G, Koening R G, Tsai V W, Fu J, Vorburger T V 1999 Dimensionalmetrology with the NISTcalibrated atomic force microscope Proc.
SPIE 367720–34[27] Gonda S, Doi T, Karusawa T, Tanimuar Y, Hisata N, Yamagishi T,Fujimoto H, Yukawa H 1999 Real-time, interferometrically measuringatomic force microscope for direct calibration of standards Rev. Sci. Instrum.70 3362–3368[28] Misumi I, Gonda S, Kurosawa T, Azuma Y, Fujimoto T, Kojima I, Sakurai T,Ohmi T, Takamasu K 2006 Reliability of parameters of associated basestraight line in step height samples: uncertainty evaluation in step heightmeasurements using nanometrological AFM Precision Engineering 30 13–22[29] Misumi I, Gonda S, Karusawa T, Takamasu K 2003 Uncertainty in pitchmeasurements of one-dimensional grating standards using a nanometrological atomic force microscope Meas.
Sci. Technol. 14 463–471[30] Yacoot A, Koenders L 2008 Aspects of scanning force microscope probes andtheir effects on dimensional measurement J. Phys. D: Appl. Phys. 41 103001[31] Beaulieu L Y, Godin M, Laroche O, Tabard-Cossa V, Grütter P 2006 Calibrating laser beam deflection systems for use in atomic force microscopesand cantilever sensors Appl. Phys. Lett. 88 083108[32] D’Costa N P, Hoh J H 1995 Calibration of optical lever sensitivity for atomicforce microscopy Rev. Sci. Instrum. 66 5096–5097[33] Mendels D-A, Lowe M, Cuenat A, Cain M G, Vallejo E, Ellis D, Mendels F2006 Dynamic properties of AFM cantilevers and the calibration of theirspring constants J. Micromech. Microeng.
16 1720–1733References[34] Senden T, Ducker W 1994 Experimental determination of spring constantsin atomic force microscopy Langmuir 10 1003–1004[35] Sader J E, Chon J W M, Mulvaney P 1999 Calibration of rectangular atomicforce microscope cantilevers Rev. Sci. Instrum 70 3967–3969[36] Weisenhorn A L, Maivald P, Butt H J, Hamsma P K 1992 Measuring adhesion, attraction, and repulsion between surfaces in liquids with an atomicforce microscope Phys.
Rev. B 45 11226–11232[37] Clifford C A, Seah M P 2005 The determination of atomic force microscopecantilever spring constants via dimensional methods for nanomechanicalanalysis Nanotechnology 16 1666–1680[38] Cleveland J P, Manne S, Bocek D, Hamsma P K 1993 A nondestructivemethod for determining the spring constant of cantilevers for scanning forcemicroscopy Rev. Sci. Instrum. 64 403–405[39] Hutter J L, Bechhoefer J 1993 Calibration of atomic-force microscope tipsRev.
Sci. Instrum. 64 1868–1873[40] Matei G A, Thoreson E J, Pratt J R, Newell D B 2006 Precision and accuracyof thermal calibration of atomic force microscopy cantilevers Rev. Sci. Instrum. 77 083703[41] Cappella B, Dietler G 1999 Force-distance curves by atomic force microscopySurf. Sci. Rep. 34 1–104[42] Israelachvili J 1992 Intermolecular and surface forces (Academic Press:London)[43] Goodman F O, Garcia N 1991 Roles of the attractive and repulsive forces inatomic-force microscopy Phys.
![](https://s.studizba.com/z.php?f=/templates/si/i/noavatar.png&w=100&h=100&t=1"){kind=avatar}
