This document discusses various techniques used to characterize surfaces including scanning probe microscopies, electron spectroscopies, vibrational spectroscopies, and ion spectroscopies. It provides details on scanning tunneling microscopy (STM) including the basic principles, instrumentation, imaging modes, applications and examples of STM used to image surface structures and molecular adsorption. Transmission electron microscopy (TEM) is also summarized briefly.

1. Chapter 5. Energetic particles-surface
interactions
Energetic particles: electron, ion, photon, atoms
1. Scanning Probe Microscopies
STM, AFM, MFM, EFM, etc.
2. Electron spectroscopy and microscopies
AES, XPS, UPS, PEEM, LEEM, SEM, TEM
3. Vibrational spectroscopies
RAIRS, MIR, HREELS
4. Ion spectroscopies
ISS, RBS, SIMS
5. Others
TPD or TDS

2. Tools for Characterization
Tools for Characterization
• Structural analysis: SEM, TEM, XRD, SAM, SPM, PEEM, LEEM,
STXM, SXPEM
• Chemical analysis: AES, XPS, TPD, SIMS, EDX, SPM
• Electronic, optical analysis: UV/VIS, UPS, SPM
• Magnetic analysis: SQUID, SMOKE, SEMPA, SPM
• Vibrational analysis: IR, HREELS, Raman, SPM
• Local physico-chemical probe: SPM
e, hv, ion tip e, hv, ion

3. Scientific issues in nanotechnologies
(Nanotech.Res. Directions: IWGN report,1999)
• Fundamental properties of isolated nanostructures
• Fundamental properties of ensemble of isolated nanostructures
• Assemblies of nanoscale building blocks
• Evaluation of concepts for devices and systems
• Nanomanufacturing
• Connecting nanoscience and biology
• Molecular electronics
Local probes with nm spatial resolution for
characterization

4. Scanning Probe Microcopy
• Scanning Tunneling Microscopy(STM): topography, local DOS
• Atomic Force Microscopy (AFM): topography, force measurement
• Lateral Force Microscopy (LFM): friction
• Magnetic Force Microscopy (MFM): magnetism
• Electrostatic Force Microscopy (EFM): charge distribution
• Nearfield Scanning Optical Microscopy (NSOM): optical properties
• Scanning Capacitance Microscopy (SCM): dielectric constant, doping
• Scanning Thermal Microscopy (SThM): temperature
• Ballistic Electron Emission Microscopy (BEEM): interface structure
• Spin-polarized STM (SP-STM): spin structure
• Scanning Electro-chemical Microscopy (SECM): electrochmistry
• Scanning Tunneling Potentiometry (SPM): potential surface
• Photon Emission STM (PESTM): chemical identification

5. References of SPM
1. P.Hansma, J. Tersoff, J. App. Phys. 61, R1 (1987)
2. Y. Kuk, P.J. Silvermann, Rev. Sci. Inst. 60, 165 (1989)
3. Scanning Tunneling Microscopy and related methods edited by R.J.
Behm, N. Garcia, and H. Rohrer (1990)
4. C.J. Chen, Introduction to scanning tunneling spectroscpy (oxford,
1993)
5. H-J Gudtherodt and R. Wiesendanger(ed.), Scanning tunneling
microscopy I,II,III (Springer,1991-1993)
6. J.A. Kuby and J.J. Boland, Surf. Sci. Rep. 26, 61 (1996)
7. R.J. Hamers, Scanning Probe Microscopy in Chemistry, J. Phys.
Chem.100, 13013 (1996)
8. G.S. McCarty and P.S.Weiss, Scanning Probe Studies of Single
Nanostructures, Chem. Rev. 99, 1983 (1999)
9. C. Bai, Scanning tunneling spectroscopy and its applications
(Springer, 2000)
10. PSIA, www.psia.co.kr/appnotes/apps.htm
11. ThermoMicroscope, www.thermomicro.com/spmguide/contents.
12. Digital Instrument, www.di.com/app_notes/full_appnotes.htm
13. H.-Y. Nie, publish.uwo.ca/~hnie/mmo/all.html

6. Interactions used for Imaging in SPM
(a) Tunneling
I~exp(kd) (d) Capacitance
C(d) ~ 1/d
(b) Forces (e) Thermal gradient
F(d) ~ various (f) Ion flow
f(d) ?
(c) Optical near fields
E ~1/d4
Resolution limits
•The property probed
•The probe size

7. Comparision of Microscopes
106
SEM OM
Vertical scale (A)
TEM
104
102
1 STM
1 102 104 106
Lateral scale (A)

8. Characteristics of Microscopies
OM SEM/TEM SPM
Operation air,liquid vacuum air,liquid,UHV
Depth of field small large medium
Lateral resolution 1 µm 1-5nm:SEM 2-10nm: AFM
0.1nm:TEM 0.1nm: STM
Vertical resolution N/A N/A 0.1nm: AFM
0.01nm: STM
Magnification 1X-2x103X 10X-106X 5x102X- 108X
Sample not completely un-chargeable surface height
transparent vacuum <10 mm
compatible
thin film: TEM
Contrast absorption scattering tunneling
reflection diffraction

9. Limits of Resolution
• HM (High Resolution Optical Microscope)
diffraction limit ~ 150 nm
• PCM (Phase Contrast Microscope)
subwave length 배율 가능
• X-ray Microscope
λ ∼1Α; Synchrotron radiation and X-ray optics
• SEM (Scanning Electron Microscopy)
Focused e-beam size > 3nm
• TEM (Transmission Electron Microscopy)
~1 A; 얇은 박막시료
• LEEM (Low Electron Emission Microscopy)
low energy e-beam; 20nm
• PEEM (Photoemission electron Microscopy)
lateral resolution~100nm; chemical analysis
• FIM (Field Ion Microscopy)
tip 형태 시료

10. Interaction of Electrons with Sample
When 20 KV e-beam is used
for Ni(Z=28).
• Auger electron :10-30A
• Secondary electron: 100A
• Backscattering electron
: 1-2 µm
• X-ray ~ 5 µm
• Penetrated electron: 5 µm
Atomic Number Interaction
Accelerating voltage Volume
Incidence angle

11. Principle: Scanning Electron Microscopy (SEM)
•Beam size: a few – 30 A
•Beam Voltage: 20-40kV
•Resolution: 10-100 A
•Magnification: 20x-650,000x
•Imaging radiations: Secondary electrons,
backscattering electrons
•Topographic contrast: Inclination effect,
shadowing, edge contrast,
E-gun
•Composition contrast: backscattering
yield ~ bulk composition
Lens Detectors
•Detections:
Secondary
- Secondary electrons: topography
electron
- Backsactering electrons:
atomic # and topography
Sample - X-ray fluorescence: composition
http://super.gsnu.ac.kr/lecture/microscopy/em.html

12. Instrumentation: SEM

13. Principle: Transmission Electron Microscopy (TEM)
•Beam size: a few – 30 A
•Beam Voltage: 40kV- 1MV
E-gun •Resolution: 1-2A
Condenser •Imaging radiations: transmitted electrons,
lens •Imaging contrast: Scattering effect
Thin •Magnification: 60x-15,000,000x
sample •Image Contrast:
Objective 1) Amplitude (scattering) contrast
lens - transmitted beam only (bright field image)
- diffraction beam only (dark field image)
Projector
lens 2) Phase (interference) contrast
- combination of transmitted and diffraction
Screen beam
- multi-beam lattice image: atomic
resolution (HRTEM)

14. Example: TEM images of Co-nanoparticles
60 nm
Self-assembled
Self-assembled
2D-monolayer
2D-monolayer
Surface
Modification
A
A
Co nanoparticles B
평균 지름 = 7.8 ±1 nm B
Self-assembled
Self-assembled
3D-multilayer
3D-multilayer
From J.I. Park and J. Cheon

15. Scanning Tunneling Microscope
Coarse positioning
device
Scanning Modes:
Piezo tube scanner
1. Constant current
X,Y,Z
2. Constant height
Tip
Current Feedback Computer
Sample amplifier controller
Sample bias
voltage
Real space imaging with atomic resolution

16. Theory of STM
J. Tersoff and D.R. Hamann, Phys. Rev. lett. 50, 1988 (1983)
Figure From J. Wintterlin
- +
ψsample ψtip
Ef
eVbias
Ef
d
It ~ ∑ |ψtip|2 |ψsample|2 e-2κd
~ ∑ |ψsample|2 δ(E-Ef) for low voltage limit; a point tip
Constant current STM image corresponds to
a surface of constant state density.

17. Tunneling probability and tunneling current
From Y. Kuk, W-tip Au(100)-5x20

18. Charge density and Potential
energy contour of Tip facing
the surface
S. Ciriaci, Phys. Rev. B 42, 7618 (1990)

19. Bias polarity : probing filled and empty states
- +
ψsample ψtip
Occupied state (HOMO)
Ef
Ef
d
Unoccupied state (LUMO)
Ef
Ef
d
J.J.Boland, Adv. Phys. 42, 129(1993)
+ -

20. Tunneling Spectroscopy
d: fixed
It ~ ∑ ρ tip (E) ρ sample (E-eV)T(E,V) dE
A
(Z)IV- x,y : Topography
di/dV~ ρsample (E): LDOS
d2i/dV2: local vibrational spectra
Si(111)-2x1
Si
Ni
Theory
I vs V (di/dV)/(I/V) vs V
J. A. Stroscio et al. Phys. Rev. Lett. 57, 2579 (1986)

21. STS spectra: Si(111)-7x7 and NH3 /Si(111)
Wolkow and Avouris, Phys. Rev. Lett, 60, 1049 (1988)

22. Current Imaging Tunneling Spectrscopy (CITS)
-Take I/V curve at each pixel of a topographic image
-Take dI/dV at the fixed bias voltage
Vb = -0.15 ~ 0.6 V
Dangling bonds in
faulted half of unit cell
(adatoms)
Vb = -0.6 ~ -1.0 V Faulted unfaulted
Dangling bonds in
second layer of atoms
(rest atoms)
Vb = -1.6 ~ -2.0 V
Si-Si back-bonds Empty(+2 V) filled ( -2V)
Topographic images

23. Instrumentation
C.J. Chen, Introduction to scanning tunneling spectroscpy (oxford, 1993)
Tip
-W tip : electrochemically etched
-Pt-Ir tip: cutting
Positioning
-fine positioning
piezoelectric ceramic (Pb(Zr,Ti)O3)
eg: PZT5H d33=5.93A/V, d31 = -2.74 A/V From S.J. Garett
δl = d31Vl/(OD-ID), δr = d33V
x,y: 0.1A z: 0,01 A resolution
-coarse positioning
louse, step motor, inch worm
Vibration isolation
-spring, viton O-ring, air table
-eddy current damping
Thermal stability
-smaller and simpler, better stability
-symmetric component
-matching the thermal coefficient

24. Tip preparation
-Electrochemical etching in 2N NaOH solution
-Ex situ : Vacuum annealing; Field emission; Ion sputtering
-In situ: high field(>-7V) scanning, controlled collision
From W. Ho group

25. Vibration isolation Y. Kuk, P.J. Silvermann, Rev. Sci.
Inst. 60, 165 (1989)
-needs ~0.01A or less
(atomic corrugation ~0.1A)
-Dapmed spring : fres =0.5 Hz
-Vition stacks :fres = 10~100 Hz
-Air tables
Damping transfer function Ts
Ts = (ν/νn’)2/[(1- (ν/νn’)2)2+ (ν/Q’νn’)2]1/2
νn’ : the resonance frequency
Q’: the quality factor of the tip-sample
junction
Rigid STM assembly
Vib. amplitude>1A
Add isolation table
Vib. amplitude <0.01 A
Internal spring and air table
Vib. amplitude<0.001 A

26. Electronics
-set the tip voltage (0-10V) and measure tunneling current (0.001~10nA)
-tip-sample separation: 2-5 A, gap resistanace : 107~1010 Ω
-scan x,y voltage: 1nm ~1000nm

27. UHV STM
From Burleigh Instrument Inc.

28. Applications of STM
• Surface geometry
• Molecular structure
• Local electronic structure
• Local spin structure
• Single molecular vibration
• Electronic transport
• Nano-fabrication
• Atom manipulation
• Nano-chemical reaction

29. Surface Structure
Various Reconstructions of Ge(100)-2x1
p(2x2)
Buckled 2x1
p(2x2)
2x1
c(4x2)
c(4x2)
J.Y. Maeng et al (2001)

30. Si(100) and Ge(100) 2x1 surface
Si(001)
at 80 K
Clean Surface Structure
Lattice Dimer Tilt π - π* Buckled-
Constant Length Angle Symmetric
Si(100) 5.43 Å 2.32 Å 70 0.66 eV 25 meV
Ge(100 5.658 Å 2.41 Å 140 1.11 eV 60 meV
)

31. Chemical identifications: bias polarity

32. Molecular Adsorption: 2+2 cycloaddition reaction
Fabrication of molecularly ordered organic films
Anisotropic optical and electrical properties
A Possible way to orient molecular devices
R.J. Hamers et al, J. Phys. Chem., 101, 1489 (1997)

33. Adsorption structure: Pyridine on Ge(100)
tunneling through space and through bond
bias dependence
Vbias = -1.0 V
Clean Ge Pyridine
Dimer LUMO
Image of π∗ bonds
Substrate
Ef
Dimer HOMO
Vbias = -1.8 V π bonds
Image of It ~ ∑ |ψsample|2 δ(E-Ef)
Substrate +
Pyridine
Ef
Vbias = -2.4V
Vbias = -2.4 V Ef
Image of Py/Ge W-Tip
Pyridine
Organic molecules reduce DOS near EF,
but increase DOS at lower energy.

34. Possible Adsorption States of Pyridine on Si(100)
Lewis base-acid reaction
Lewis base-acid reaction
-δ
+δ
[4+2] cycloaddition
[4+2] cycloaddition
Lu et al. New. J. Chem. 26. 160 (2002)

35. Comparison of Theoretical STM Images with Experiment
θ = 0.25 ML: experiment c(4x2) model theory
θ = 0.5 ML: experiment p(2x2) model theory

36. Long chain molecules on surface
Left A 3nm x 3nm image of docosanol taken at the liquid-
solid interface on graphite. The black bar is superimposed
over one molecular length, measured to be 3.0 + 0.2nm.
The left-hand trough (marked in the image) signifies the
alcohol group, which show up slightly darker relative to the
rest of the hydrocarbon chain. The individual bright
Leanna C. Giancarlo, Hongbin Fang, Luis (yellow) spots along the molecular axis depict individual
Avila, Leonard W. Fine, hydrogen atoms. You can actually count them and get 22
and George W. Flynn, J. Chem. Ed., 77, hydrogens per molecule (only one hydrogen per carbon is
66-71 (2000) visible to the STM since the second hydrogen on each
carbon is pointing down into the graphite and therefore not
seen in the image).

37. STM of Metal phthalocyanines: Fe(II) d6 Ni(II) d8
Figure 3 Top view STM images of a 0.4 nm thick layer of NiPc and
of 0.3 nm of FePc on Au(111) obtained with a W tip. Both samples Figure 2 Schematic orbital energy diagram for
had MPc layers that had once been exposed to air. The gray scale several transition metal phthalocyanine
extends over 0.3 nm. For NiPc the sample bias was +0.50 V and the complexes. In the case of iron(II), a single orbital
tunneling current was 300 pA. For FePc the sample bias was +0.10 configuration cannot be used to describe the
V and the tunneling current was 1.6 nA. The image was Fourier ground state, and at least two configurations are
filtered to reduce noise. required. This situation is represented
diagramatically by use of a broken × to indicate
partial occupation of an orbital by an electron,
while a full × represents near complete
Xing Lu and K. W. Hipps, occupation by a single electron. This diagram is
J. Phys. Chem. B, 101 (27), 5391 -5396, 1997 based on ref 1, 3, 30, and 31.

38. In-situ Monitoring of Self-assembly
Self-directed growth of Nanostructures
Wolkow et al, Nature, 406, 48 (2000)

39. Single Molecule Vibrational Spectroscopy
Inelastic electron tunneling spectroscopy (IETS)
hv/e
I
V
dI/dV
V
dI2/dV2
V
Vibration excitation of the molecule occurs when tunneling
electrons have enough energy to excite a quantized vibrational level
Inelastic tunneling channel
B.C. Stipe. et. al., Science 280, 1732 (1998)

40. Atomic Manipulation by STM
-high electric field: polarize
the molecule and make it jump from
the surface to the tip vice versa. Iron on Copper (111):
-van der Waals force between the tip
and the atom use to drag the atom
- Circular corral (radius=71.3A)
48 Fe atoms
- Quantum-mechanical
interference patterns
M.F. Crommie, C.P. Lutz, D.M. Eigler. Science 262, 218-220 (1993).

41. Single-Bond Formation by STM
H.J. Lee and W. Ho, Science, 286, 1719(1999)

42. Real Space Imaging of Two-Dimensional
Antiferromagnetism On the Atomic Scale
Weisendanger et al, Science 288, 1805 (2000)
Nonmagnetic
W tip
Magnetic
W tip

43. Conductance : Landauer formula
µ2
eVmol eV
µ1 µ2 µ1
I = (2e/h)∫dE T(E,V) [f(E-µ1)-f(E-
µ2)]
•F(E): Fermi function
•T(E,V): transmission function
molecular energy levels and their coupling
to the metallic contacts
µ1, µ2 : electrochemical potentials
µ1= Ef- eVmol
µ2 =Ef+eV- eVmol
W. Tian et al, J. Chem. Phys. 109, 2874(1998)

44. Conductance of molecular wire: STM
•Tip bias voltage = 1V,
•Tunnling current = 10 pA
L. A. Bumm et al , Science 271, 1705 (1996).

45. Electronic Properties of Carbon Nanotubes
Constant LDOS
Metallic SWNT
Semiconducting
SWNT

46. STM Topograph of Quantum Dot
Ge pyramid containing
~2000 Ge atoms on Si(100)
Ge dome grown by PVD
on a 600 C Si(100)
R.S. Williams et al, Acc. Chem. Res. 32, 425 (1999)

47. STM Images of Ni Clusters at Different
Sample Bias Voltages

48. STS and STM of
Self-assembled Co-nanoparticles
Tip on self-assembled monolayer
Tip on a Co nanoparticle
I vs V
dI/dV vs V
Pileni et al, Appl. Surf. Sci. 162/163, 519 (2000)

49. Tunneling Spectroscopy of InAs QD
STM
T=4.2K
Optical
d = 32A
S-like
P-like
Ec=0.11 eV: single electron charging energy U. Banin et al, Nature,
Eg=1.02 eV: nanocrystal band gap 400, 926 (2000)

50. Interactions between Sample and Tip
in Force Microscopy
vdW force magnetic or adhesion elastic and
attractive electrostatic bonding plastic properties
ionic repulsion forces friction forces
f Contact
van der Waals force
Intermitant contact
r f(r) ~ -1/r6 +1/r12
total force on sample ~ 10-7 ~10-11 N
Noncontact

51. Force vs. Distance
f
r
Vacuum
touching
untouch
Air
Capillary
Pull off force
Slope: elastic modulus of soft Contamnated
sample or force constant k of in air
cantilever

52. Atomic Force Microscope (AFM)
•Sample: conductor, nonconductor, etc
•Force sensor: cantilever
•Deflection detection
- photodiode interferometry (10-4A)
- STM

53. Mode of Operation Force of interaction
Contact strong (repulsive): constant force
or constant distance
Noncontact weak(attractive): vibrating probe
Intermittent contact strong(repulsive): vibrating probe
Lateral force frictional forces exert a torque on
the scanning cantilever
Magnetic force the magnetic field of the surface
Thermal scanning the distribution of thermal conductivity

54. Force Sensor: Cantilever
•Material: Si , Si3N4
•Shape: pyramidal, conical tip
•Typical Dimension:
100-200 µm
1-4 µm
10 µm
•Stiffness
- soft: contact mode
∼20nm
- stiff: vibrating (dynamic force)
mode
•Spring constant (k):
0.1-10N/m (atom-atom k ~10N/m)
•Resonance frequency: 10~100kHz
eg: f = (/2π)(k/m)1/2 From DI
m=1µg, k=0.1 N/m, f=100kHZ

55. Nanotube tip
Review: www.psia.co.kr/kr
- attaching with glue
- in situ CVD grwoth
(a) AFM image of 2 nm tall, 10 mm wide, and 100 nm spaced silicon-oxide
H.Dai et al, Nature 384, 174 (1996) (light) lines fabricated by a nanotube tip. Bias voltage = – 9 V; speed = 10
APL 73, 1508 (1998) m/s; cantilever amplitude during lithography = 0.55 nm; cantilever
amplitude = 9.6 nm. (b) Silicon oxide ``words'' written by the nanotube tip.

56. Image Artifacts
•Tip imaging
•Feedback artifacts
•Convolution with other physics
•Imaging processing
How to check ?
•Repeat the scan
•Change the direction
•Change the scan size
•Rotate the sample
•Change the scan speed AFM image of random noise. Left
image is raw data. Right image is a
false image, produced by applying a
narrow bandpass filter to the raw data
www.psia.co.kr/appnotes/apps.htm

57. Scanning Modes of AFM
Contact Noncontact Vibrating (tapping)
•Cantilever soft hard hard
•Force 1-10nN 0.1-0.01nN
•Friction large small small
•Distance <0.2nm ~ 1nm >10nm
•Damage large small small
•Surface hard surface soft or elastic surface
Polymer latex
particle on
mica
From Digital Instrument

58. Vibrating Cantilever (tapping) Mode
•Vibration of cantilever around its resonance frequency
•Change of frequency (fo) due to interaction between sample
and cantilever
Resonance Frequency
keff = k0 - dF/dz
feff = 2π(keff /m)1/2
•Amplitude imaging
•Phase imaging
•Removal of lateral force contribution

59. H.-Y. Nie, http://publish.uwo.ca/~hnie/mmo/all.html

60. Applications of SPM
• Surface morphology, especially for insulators
• Lateral, adhesion, molecular and magnetic forces
• Temperature, capacitance, and surface potential
mapping
• Nano-lithography
• Surface modification and manipulation
• Imaging of biomolecules, and polymers

61. Atomic resolution AFM
AFM (contact mode): AFM (non-contact mode):
Au(111) polycrystalline film Atomic resolution on Si(111)7x7
on a glass substrate
From Omicron Inc.

62. STM and AFM Images of Co-Nanoparticles
STM: on H/Si(111) AFM: on HOPG TEM: on Carbon grid
Co-nanoparticle stripes prepared
By Mirco Contact Printing
AFM image
UHV-STM image (200 nm x 200 nm)
after annealing under 500 °C S.S.Bae et al (2001)

63. Applications to biological system
DNA and RNA analysis; Protein-nucleic acid complexes; Chromosomes; Cellular
membranes; Proteins and peptides; Molecular crystals; Polymers and biomaterials; Ligand-
receptor binding. Bio-samples have been investigated on lysine-coated glass and mica
substrate, and in buffer solution. By using phase imaging technique one can distinguish the
different components of the cell membranes.

64. Force Measurement of DNA strands
Baselt et al, J. Vac. Sci. Tech. B14, 789 (1996)

65. Manipulation of Nanoparticles by
AFM
Ref 15 in G.S. McCarth and P.S.Weiss, Chem. Rev. 99, 1983 (1999)

66. Dip pen nanolithography using AFM
C. Mirkin et al, Science 283, 661
Read Prof I. Choi, lecture note (spring 2002) (1999); 295, 1702 (2002)
Figure 1. AFM images and height profiles of lysozyme
nanoarrays. (A) Lateral force image of an 8 µm by 8 µm
square lattice of MHA dots deposited onto an Au substrate.
The array was imaged with an uncoated tip at 42% relative
humidity (scan rate = 4 Hz). (B) Topography image (contact
mode) and height profile of the nanoarray after lysozyme
adsorption. A tip-substrate contact force of 0.2 nN was used
to avoid damaging the protein patterns with the tip. (C) A
tapping mode image (silicon cantilever, spring
contant = ~40 N/m) and height profile of a hexagonal
lysozyme nanoarray. The image was taken at a scan rate of
0.5 Hz to obtain high resolution. (D) Three-dimensional
topographic image of a lysozyme nanoarray, consisting of a
line grid and dots with intentionally varied feature
dimensions. Imaging was done in contact mode as
described in (B).

67. Conductive AFM
Conductive AFM is used for collecting
simultaneous topography imaging and
current imaging. Specifically, standard
conductive AFM operates in contact AFM
mode. Variations in surface conductivity
can be distinguished using this mode.
Conductive AFM operates in contact AFM
mode by using a conductive AFM tip. The
contact tip is scanned in contact with the
sample surface. Just like contact AFM,
the Z feedback loop uses the DC
cantilever deflection signal to maintain a
constant force between the tip and the
sample to generate the topography
image. At the same time, a DC bias is
applied to the tip. The sample is held at
ground potential. The built-in pre-
amplifier in the scanner head measures
the current passing through the tip and
sample.
http://www.thermomicro.com/spmguide/1-5-0.htm#NANO

68. AFM/STM lithography
resist의 표면 topography에도 매우 민감합니다. 대부분 E-
beam resist는 주입된 전자 수에 민감하므로 전압에 의하여
제어보다 전류를 집적 제어하는 것이 보다 재현성 있는 패턴
을 얻을 수 있습니다. 따라서 AFM과 STM를 결합하여 resist
표면을 일정한 거리와 힘를 유지하도록 하면서resist 막의 두
께가 변화더라도 전류를 일정하게 유지시키도록 ( 20 pA ~ 1
nA ) 탐침의 전압을 (10~100 V) 변화 시키는 독립적인
feedback loop를 도입하였습니다.(STM mode). 두 제어 방
법을 결합하여 패턴 전체에 걸쳐 전자의 주입양(electron
dose) 일정하게 유지하여 수십 nm 수준의 패튼의 재현성을
얻었을 뿐만 아니라 기존 E-beam lithography에서 발생하는
depth of focal length 문제를 해결하였습니다.
From http://www.psia.co.kr/

69. AFM-tip-induced Local Oxidation on Si
Ph. Avouris et al, App. Phys. A 66, S659 (1998)

70. Lateral Force Microscopy
•Contact mode
•Detect vertical and lateral
twisting due to friction
•Simultaneous AFM & LFM
imaging
•Information about friction
High resolution topography
(top) and Lateral Force mode
(bottom) images of a
commercially avail-able PET
film. The silicate fillers show
increased friction in the
lateral force image.
www.tmmicro.com/tech/modes/lfm.htm

71. Force Modulation Microscopy
•Contact AFM mode
•Periodic signal is applied to either to tip or sample
•Simultaneous imaging of topography and material properties
•Amplitude change due to elastic properties of the sample
PSIA, www.psia.co.kr/appnotes/apps.htm

72. Phase Detection Microscopy
Phase imaging is useful for differentiating
between component phases of composite
materials. The bulk of the wood pulp shown in
this figure consists of cellulose microfibrils
that are highlighted by phase imaging. In
addition, a lignin component -- not apparent in
From Digital Instrument the topography -- appears as areas of light
contrast atop the cellulose component
•Intermittant-contact AFM mode
•Monitoring of phase lag between the cantilever oscillation
(solid wave) relative to the piezo drive (dashed wave).
•Simultaneous imaging of topography and material properties
•Change in mechanical properties of sample surface

73. Chemical Force Microscopy
CH3 COOH
(A) topography
(B) friction force using a tip modified with a COOH-terminated SAM,
(C) frinction force using a tip modified with a methyl-terminated SAM.
Light regions in (B) and (C) indicate high friction; dark regions indicate low
frinction.
A. Noy et al, Ann. Rev. Mater. Sci. 27, 381 (1997)

74. Magnetic Force Microscopy
Glass Hard Disk Sample
dF/dz =dFm/dz + dFvdw/dz,
•Ferromagnetic tip: Co, Cr
•Noncontact mode (>100A) AFM
•vdW force: short range force image
•Magnetic force: long range force
small force gradient
•Close imaging: topography
•Distant imaging: magnetic properties MFM
image
http://www.tmmicro.com/tech/index.htm

75. Scanning Hall Probe Microscopy
z
H y
++++++ RH= Ey/jxH
i x
-------- = -1/ne
Ey F= -evxH
The spots correspond to individual
magnetic lines or vortices that are
formed in a superconducting film of
LaSrCaCuO
This probe allows one to measure microscopic magnetic patterns by using a
submicron Hall probe to sense local magnetic fields. Fields as low as 0.1 gauss
with 0.3um spatial resolution can be achieved. It competes with magnetic force
microscopy which might have superior resolution but is not calibrated and with
scanning SQUID microscopy which has higher magnetic field sensitivity but
poorer spatial resolution.
Hans Hallen and Albert Chang. (Bell lab), Applied Physics Letters, 61, pg 1974
(1992).

76. Electrostatic Force Microscopy(EFM)
Scanning Kelvin Probe Microscopy (SKPM)
Scanning Tunneling Potentiometry (STP)
Scanning Maxwell Microscopy (SMM)
Metallic tip
Bias Voltage
• Ferroelectric materials
• Charge distribution on surfaces
• Failure analysis on the device
http://www.tmmicro.com/tech/index.htm

77. Theory of EFM
Electrostatic force between the sample
and the tip
(Fcapacitance = dEc /dz , Ec = CV2/2)
F = Fcapacitance + F coulomb
= (1/2)V2(dC/dz) + (1/4πε z2)QsQt
= (1/2) (dC/dz) (Vdc+Vac cos ωt)2
- (1/4πε z2)Qs (Qs+CVdc+CVaccos ωt)
= (1/2) (dC/dV) (V 2dc+ (1/2) V2ac)
- (1/4πε z2)Qs (Qs+CVdc)
+ (2Vdc dC/dz - QsC /4πε z)Vaccos ωt
+ (1/4)dC/dzV2ac cos 2ωt
•Ist harmonic term
- Surface potential (Vdc )
- surface charge (Qs)
•2nd harmonic term
- dC/dz : doping concentration

78. Scanning Capacitance Microscopy
(SCM)
Transistor Oxide Thickness
Metallic tip
Contact
Topograph SCM
• LC capacitance circuit
• Doping concentration
• Local dielectric constant
http://www.psia.co.kr/appnotes/apps.htm

79. Scanning Thermal Microscopy
• Subsurface defect review
• Semiconductor failure analysis
• Measure conductivity differences in copolymers,
surface coatings etc

80. Hybrid Tools: AFM inside SEM
M.F. Yu et al, Nanotechnology 10, 244 (1999)

81. Nearfield Scanning Optical Microscopy
Topography and Optical properties
Glass
hv
Detector Al
φ=60-200nm
d
Fluorescence image of
•Near field: d<<λ
a single DiIC molecule.
•Resolution ~ d and φ
Image courtesy of P.
•Approach: shear force
Barabara/Dan Higgins
http://www.psia.co.kr/data/nsom.htm

82. Scanning Electrochemical Microscopy
From Prof. J. Kwak
Electrochemistry
Surface structure
Electrochemical deposition
Corrosion

83. Photon Emission STM
Photon detector
A
A
FEEDBACK
Local chemical environment
G.S. McCarty and P.S. Weiss, Chem. Rev. 99, 1983 (1999)

84. BEEM (Ballistic Electron Emission Microscopy)
A Ballistic Electron
A Ef
gap
FEEDBACK
Tip Base Collector(Si)
STP (Scanning Tunneling Potentiometry)
A ..
.
.
FEEDBACK

85. Summary
STM
• real space imaging
• high lateral and vertical resolution
• STS probe electronic properties
• sensitive to noise
• image quality depends on tip conditions
• not true topographic imaging
• only for conductive materials
AFM and others
•apply to nonconducting materials : biomolecules, ceramic
• real topographic imaging
• probe various physical properties: magnetic, electrostatic,
hydrophobicity, friction, elastic modulus, etc.
• can manipulate molecules and fabricate nanostructures
• low lateral resolution ~50A
• contact mode can damage the sample
• image distortion due to the presence of water
• difficulties in chemical identification

86. Future Directions for
Characterization of Nanosystems
• Instrument for analysis of biomolecules, and polymers
• 3-D structure determination
• Nanostructure chemical determination
• Functional parallel probe arrays
• Standardization and metrology
• New nano-manipulator
• Non-SPM probes that use ions or electrons
• In-situ nondestructive monitoring techniques