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Scanning Probe Microscopy and its Applications 奈奈理量奈奈量理 http://www.phys.

1 Scanning Probe Microscopy and its Applications 奈奈理量奈奈量理 /password.htm Tel : ishwang@phys.sinica.edu.tw 料

2 奈 1 2 理 3 數例奈奈量奈奈

3 (Scanning Probe Microscopy) Scanning Tunneling Microscopy (STM) --- G. Binnig, H. Rohrer et al, (1982) Near-Field Scanning Optical Microscopy (NSOM) --- D. W. Pohl (1982) Atomic Force Microscopy (AFM) --- G. Binnig, C. F. Quate, C. Gerber (1986) Scanning Thermal Microscopy (SThM) --- C. C. Williams, H. Wickramasinghe (1986)) Magnetic Force Microscopy (MFM) --- Y. Martin, H. K. Wickramasinghe (1987) Friction Force Microscopy (FFM or LFM) --- C. M. Mate et al (1987) Electrostatic Force Microscopy (EFM) --- Y. Martin, D. W. Abraham et al (1988) Scanning Capacitance Microscopy (SCM) --- C. C. Williams, J. Slinkman et al (1989)

4 1. All SPMs are based on the ability to position various types of probes in very close proximity with extremely high precision to the sample under investigation. 2. These probes can detect electrical current, atomic and molecular forces, electrostatic forces, or other types of interactions with the sample. 3. By scanning the probe laterally over the sample surface and performing measurements at different locations, detailed maps of surface topography, electronic properties, magnetic or electrostatic forces, optical characteristics, thermal properties, or other properties can be obtained. 4. The spatial resolution is limited by the sharpness of the probe tip, the accuracy with which the probe can be positioned, the condition of the surface under study, and the nature of the force being detected.

5 不 thermocouple tip sample

6 利力

8 1. Introduction Outline 2. Scanning tunneling microsocopy (STM) and tunneling spectroscopy (STS) 3. Atomic force microscopy (AFM) 4. Magnetic force microscopy (MFM) and electrostatic force microscopy (EFM) 5. Non-contact AFM 6. Near-field scanning optical microscopy (NSOM) 7. Other SPMs 8. SPM in biology 9. Applications in electrochemistry 10. Other applications in nanotechnology

Text book Dawn Bonnell, "Scanning Probe Microscopy and Spectroscopy: Theory, Techniques, and Applications". Wiley-VCH 2001. Reference books 1. C.

9 Text book Dawn Bonnell, "Scanning Probe Microscopy and Spectroscopy: Theory, Techniques, and Applications". Wiley-VCH Reference books 1. C. Julian Chen, "Introduction to Scanning Tunneling Microscopy", Oxford Morris, Kirby, and Gunning, "Atomic Force Microscopy for Biologists: Imperial College Press Grading Mid-term exam 50% Term report (oral, paper) 50%

10 SPM (SEM) SEM SPM.... 度 (x, y) 0.5 m 2nm nm 度 (z) N/A N/A 0.01nm 率 Sample 冷.. 理 Sample 不,,, 不落

11 1. SPM 度, z, 不 20 nm 度, 不度 10 nm 更, SPM 不 0.01 nm 度 2., 金理,, 理, 狀不, 量 ( ) SPM 不, 不理, 更, 3. SPM 不不行量 4. (sensor) STM AFM 量理 ( : 度力 ) 5. SPM 度落料不 SPM 料 Z 行不 (1-10 µm) SPM 暴露料 SPM 力 SPM 度不 SEM

12 Field Ion Microscopy (FIM) - W Tip

13 Transmission Electron Microscopy (TEM)

14 Scanning Tunneling Microscopy References 1. G. Binnig, H. Rohrer, C. Gerber, and Weibel, Phys. Rev. Lett. 49, 57(1982); and ibid 50, 120(1983). 2. J. Chen, Introduction to Scanning Tunneling Microscopy, New York, Oxford Univ. Press (1993). 3. ) )

15 Tunneling Classical Quantum Mechanics Tunneling current Tunneling current I t I t (V/d)exp(-Aφ 1/2 d) A = (ev) -1/2 Å -1 I t = 10 pa~10na V = 1mV ~ 3V d 1Å, I t 10

16 Schematics of STM

17 STM Images of Si(111)-(7 7) Empty-state image Filled-state image

18 Atomic Model of Si(111)-(7 7) Top view 26.9 A O 7.7 A o C C C E E E E C 112 E E C C Si adatom Si rest atom with a dangling bond Side view C E E C dangling bond 2nd layer rest atom faulted half unfaulted half

19 Atomic Structure of the Pt(001) Surface Surface Science 306, 10 (1994).

20 Surface States at Cu(111) Nature 363, 524 (1993).

21 Single-Wall Carbon Nanotubes

22 Electronic Structure of Single-Wall Nanotubes 1. Armchair nanotubes (n,n) metallic 2. Zigzag nanotubes (n,0) metallic, when n=3q semiconducting, otherwise 3. Chiral nanotubes (n,m) metallic, when m=n+3q

23 Electronic Structure of Single-wall Nanotubes Nature 391, 59 (1998).

24 Atomic Manipulation with STM Nature 344, 524 (1990)

26 Quantum Correl M.F. Crommie et al., Science 262, 218 (1993).

28 Site Hopping of O 2 on Si(111)-7x7

29 Site Hopping of O 2 Molecule on Si(111)-(7x7) t = 0s t = 683s t = 730s t = 742s STM images B i I * * i I f B f Atomic model Si adatom Si rest atom Potential diagram ev B i ev ev I * * i I f B f

30 Reversible Surface Phase Transition Pb/Si(111)

31 Size Effects on the Pb-Covered Si Islands 200 K Scale bar: 5 nm 267 K I.S. Hwang, et al., Phys. Rev. Lett. 93, (2004)

32 Electrochemical Scanning Tunneling Microscopy Angew. Chem. Int. Ed. 40, 1162 (2001).

Single-Atom Tip Properties of a single-atom tip:

All that defines a highly coherent source that

33 Single-Atom Tip Properties of a single-atom tip: atomic size emission area, small angular divergence, high brightness, generation of one ion or electron at a time. All that defines a highly coherent source that should prove to be quite useful for microscopy with charged particles. FIM FEM

34 Traditional State-of-the art Ideal electron point source Traditional State-of-the art Ideal ion point source

Pd-Covered W(111) Single-Atom Tips Vacuum process 1.

Deposition of 1-2 monolayer of Pd. 3. Annealing. 1. Thermally and chemically stable.

A well-defined structure after each regeneration. 4. Long lifetime.

35 Pd-Covered W(111) Single-Atom Tips Vacuum process 1. Preparation of a clean W(111) surface. 2. Deposition of 1-2 monolayer of Pd. 3. Annealing. 1. Thermally and chemically stable. 2. The single-atom tip can be regenerated if damaged or contaminated. 3. A well-defined structure after each regeneration. 4. Long lifetime. Field Ion Microscopy (FIM) Regeneration 1 st layer 2 nd layer 3 rd layer Fu, Cheng, Nien, Tsong, Phys. Rev. B 64, (2001).

36 力 Atomic Force Microscopy (AFM) F = k z F = N k = N/m References 1. G. Binnig, C. F. Quate, and C. Gerber, Phys. Rev. Lett. 56, 930(1986). 2. P. Grütter, H.J. Mamin and D. Rugar, in Scanning Tunneling Microscopy II, edited by R. Wiesendanger and H.-J. Güntherodt, Berlin Heidelberg: Springer-Verlag, 151 (1992) (4), 7 (2005)

37 力離力 1) 力 2) 力力 1) 力 2) 力 3) 力 4) 力 Lennard-Jones potential φ(r) = - A/r 6 + B/r 12

38 Micro-Fabricated AFM Tips V-shaped Materials: Si, SiO 2, Si 3 N 4 Ideal Tips: hard, small radius of curvature, high aspect ratio Pyramid Tip Ultrasharp Tip Rectangular-shaped Diamond-coated Tip

40 AFM

41 AFM Images CD pits Integrated circuit Chromosomes DVD pits Bacteria DNA

42 Native Membrane Proteins (a) Ion-driven rotors from spinach chloroplast and (b) Illyobacter tartaricus FoF1-ATP synthase. (c) High-light-adapted native photosynthetic membrane from Rhodospirillum photometricum. (d) Perfringolysin O pore complexes. (e) Dimeric bovine rhodopsin (dotted ellipse) in native disc membranes. (f) Extracellular surface of gap junction hemichannels.

43 UHV-AFM constant-frequency-shift image (df= -38 Hz) Lantz et al., Science 291, 2580 (2001)

44 Force-Distance Curve

45 Single Molecule Force Spectroscopy

46 AFM in Biology Individual bacteriorhodopsin molecules in water Science 288, 143(2000)

47 Nano-Lithography with an AFM tip Physics Department National Tsing Hua University

48 F.S.-S. Chien et al., APL 75, 2429 (1999)

49 IBM Nanodrive Project P. Vettiger & G. Binnig, Scientific American, pp 35-41, Jan. 2003

51 Magnetic Force Microscopy (MFM) F = (m )H The tip is scanned several tens or hundreds of nanometers above the sample, avoiding contact. Magnetic field gradients exert a force on the tip's magnetic moment, and monitoring the tip/cantilever response gives a magnetic force image. To enhance sensitivity, most MFM instruments oscillate the cantilever near its resonant frequency with a piezoelectric element. Gradients in the magnetic forces on the tip shift the resonant frequency of the cantilever. Monitoring this shift, or related changes in oscillation amplitude or phase, produces a magnetic force image. Tips: silicon probes are magnetically sensitized by sputter coating with a ferromagnetic material. Resolution 10~25 nm. Applications: hard disks, magnetic thin film materials, micromagnetism.

52 Magnetic Force Microscopy AFM MFM Bits (50 nm) on a magneto-optical disk. Scan area (5 m 5 m)

53 (NSOM)

54 Topography NSOM Image

55 度 (SThM)

56 Scanning Thermal Microscopy

57 (SCM)

58 SCM CV Curve

59 J. Isenbart et al., Appl. Phys. A 72, S243 (2001).

60 Cantilever-Based Chemical and Biological Sensors silicon cantilever array Molecular recognition DNA hybridization Receptor-ligand binding surface stress changes Science 288, 316 (2000)

single-virus particles Appl. Phys. Lett.

61 Virus detection using nanoelectromechanical devices Mass sensitivities on the order of g/hz Detect the mass of single-virus particles Appl. Phys. Lett. 85, 2604 (2004) l=6 µm, w=0.5 µ m, t=150 nm with a 1 µm x 1 µm paddle. Scale bar corresponds to 2 mm.

62 Vacuum Technology Needs for UHV (<10-9 torr) 1. Clean surfaces 2. Long mean free paths for particles Pressure P 1 torr (mm of Hg) = 133 Pa Flux F(atoms/cm 2 sec) = 2.63 x P(Pa)/ M ( g / mole) T = 3.51 x P(torr)/ M ( g / mole) T N 2 (M = 28) at T = 293K at 10-6 torr, F = 3.88 x molecules/cm 2 sec ~ 1/3 monolayer/sec Exposure 1 langmuir (L) = 10-6 torr sec Preparation of a clean surface in UHV 1. Cleavage 2. Heating 3. Ion bombardment (sputtering) --- typically Ar ions 4. Chemical processing

64 Rough vacuum 1 atm 10-2 torr Mean free path << the diameter of the conducting tube. The mutual interaction of the particles with one another determines the character of the flow. The viscosity or inner friction of the streaming material plays the dominant role. Macroscopic direction of flow of the streaming gas. Medium vacuum 10-2 torr 10-6 torr Mean free path ~ the diameter of the conducting tube. High vacuum 10-6 torr 10-9 torr Ultra-high vacuum (UHV) < 10-9 torr Mean free path >> the diameter of the conducting tube. Gas particles can have any random direction.

65 The Structure of Surface Atoms on a surface of a solid have an environment that differs markedly from that of atoms in the bulk of the solid. They have fewer neighbors than do bulk atoms. On clean surface, two important structure changes can occur. 1.Bond-length contraction or relaxation 2.Reconstruction

66 Bond-length Contraction or Relaxation 1. In vacuum, virtually all surfaces relax. The spacing between the first and second atomic layers is significantly reduced from the spacing characterizing the bulk. 2. For a close-packed metal with a less close-packed surface, the interlayer spacing between the topmost and the second atomic layer is smaller than the bulk spacing. The perturbation caused by this surface relaxation propagates a few layers into the bulk. In fact, there is often a compensating expansion between the second and the third metal layer (on the order of 1%), accompanied by a small but detectable change in the next layer.

67 Relaxation Reconstruction Missing row reconstruction

Reconstruction The surface can assume an atomic

structure one would expect if the bulk structure

For semiconductor surfaces, which are covalently

surface cannot easily be satisfied except

1). Si(001) Many metal surfaces also reconstruct.

68 Reconstruction The surface can assume an atomic structure that differs fundamentally from the structure one would expect if the bulk structure terminated abruptly at the surface. For semiconductor surfaces, which are covalently bonded, the dangling bonds created at the surface cannot easily be satisfied except through more drastic rearrangements of these atoms. Example: Si(111)-7 7, Ge(111)-c(2 8), Si(001)-(2 1). Si(001) Many metal surfaces also reconstruct. Examples: Ir(100), Pt(100), Au(100) Hexagonally close-packed surface layer on square lattice. Ir(100)-(1x5) Pt(100)

69 GaAs(110)-(1x1) Top view Side view Sphere model (side view) Nonreconstructed Relaxed

70 Si(111)-(2x1) Top view Side view Sphere model (side view) Nonreconstructed π Chain π Chain π Chain model

71 Lowest Energy Geometries proposed for the Si n (n 11) neutrals in the literature

72 Theoretical Model of Si 1000 Clusters Phys. Rev. B 57, 3799 (1998)

73 Theoretical Model for Metal-encapsulated Si n Clusters Phys. Rev. Lett. 87, (2001)

74 Miller Indices of a Plane

75 Face-Centered Cubic (fcc) Crystal Surfaces

76 The Five Surface Net

77 Notation of Surface Structures 1. If the translation vectors of the surface, a and b, a = Ma, b = Nb, where a and b are the translation vectors of the ideal, unreconstructed surface. The nomenclature for this structure is (M N). If, in addition, the surface net is rotated with respect to the underlying substrate lattice by an angle degrees, the notation becomes (M N)R. If the surface net is best described using a centered, rather than a primitive net, this is indicated as c(m N). If the overlayer consists of an adsorbate, rather than simple reconstructed substrate atoms, this is also usually indicated. An arrangement of surface atoms identical to that in the bulk unit cell is called the substrate structure and is designated (1 1) (i.e. unreconstructed). 2. The surface unit-cell vectors a and b can be expressed in terms of the unit-cell vectors, a and b, obtained from the bulk projection. a = m 11 a + m 12 b, b = m 21 a + m 22 b, M = m m m m A surface structure that has a unit cell different from the bulk-projected substrate unit cell is often called a superlattice. (2 2) correspond to the matrix notation.

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