Coarse approach
mechan ism
Referenc e
S
c
a
feedback
n
n data
e
r
Signa l
-
Senso r
Sample
Figur e 3.1. Sche matic show ing all major
componen ts of an SPM. In this example,
feedback is used to move the sensor
Figure 3.1. Schematic
showing all major components of an SPM.
verticall y to maintain a cons tant signa l.
this example, feedback
is used
to move
the
sensor
vertically to
Vertical
displacement
of the
sensor
is taken
as topographical data.
maintain a constant signal. Vertical displacement of the sensor is
taken as topographical data
In
z
E

3
3
2
1
x

Figure 3.2. Deformation of piezoelectric material in an electric field
and the defining coefficients.
Z
Y
X
Figure 3.3. Tripod design of SPM scanner with the sensor tip located
at the bottom.
Figure 3.4. Tube scanner. (From Ref. 6 by permission of American
Institute of Physics.)
Piezoe lectric
tube
carrier
rail
Figur e 3.5. An exa mple of an inertia
motor used for coarse approach in SPM.
Figure 3.5. An example of an inertia motor used for coarse approach
in SPM.
V
t
Figur e 3.6. One pos sible wavefo rm f or the
inertia motor. The carrier is fi rst pushed
wit h a nea r cons tant speed and then the rail
wit hdraws with great acceleration to cause
Figure 3.6. One possible
waveform
inertia motor.
sli pping. The
carrier will for
m ovethe
in opposite
dira
ection
rever sing the
volt ageand
po lathen
rit y. the rail
is first pushed with
nearbyconstant
speed
The carrier
withdraws
with great acceleration to cause slipping. The carrier will move in
opposite direction by reversing the voltage polarity.
Figure 3.7. Left: Constant current mode, with feedback turned on to
maintain a constant tunneling current. Right: Constant height mode,
feedback is turned off. (From Ref. 8 by permission of American
Institute of Physics.)
d
h
As
O
z
Ac
E
-
R
Figur e 3.8. Sche matic for the feedback loop used in
constant current mode of STM.
Figure 3.8. Schematic for the feedback loop used in constant current
mode of STM.
V(x)
III
II
I
Ae ikx
Eeikx
Cekx +
De -kx
Be-ikx
x
0
d
Figur e 3.9. Tunne li ng o f a single electron
through a potential barrier.
Figure 3.9. Tunneling of a single electron through a potential barrier.
1
Ef1
2
-
e
eV
Ef2
V
Figur e 3.10. Tunne li ng o f electrons between two
metals .
Figure 3.10. Tunneling of electrons between two metals.
f(E)
1
df
dE
~3.5kBT
f(E)
0
E
Ef
Figur e 3.11. Fermi-Dir ac distribu tion and its
derivative.
Figure 3.11. Fermi-Dirac distribution and its derivative.
Figure 3.12. The density of states of superconducting Al. One of the
first obtained by tunneling spectroscopy. The peak position roughly
estimates . (From Ref. 9 by permission of American Physical
Society.)
B
N
S
N
S
N
S
Figur e 3.13.
Formation of vortices in a
sup ercondu ctor.
S r egion
is
still
sup ercondu cting , but the area whe re the field
pene trates (N) has now beco me nor ma l (vor tex
Formation
of vortices in a superconductor.
core).
Figure 3.13.
S region is
still superconducting, but the area where the field penetrates (N) has
now become normal (vortex core).
Figur e 3.14 . STM vortex im age of NbSe2
taken at 1.8K, wit h an external field of 1T.
Figure 3.14 . STM vortex image of NbSe2 taken at 1.8K, with an
external field of 1T. (From Ref. 11 by permission of American
Physical Society.)
b
a
a
c
d
Figur e 3.15. Co a toms on smooth Cu(111)
The Cu atoms are moved to the desired
Figure 3.15. Co surface.
atoms
on
smooth Cu(111) surface. The Co atoms are
pattern by carfully manipulating the positi on and
moved to the desired
by carefully
manipulating
volt agepattern
of t he STM
tip. Note how
the electron the position
wave
s in tip.
the background
arethe
being
focus ed waves
by
and voltage of the
STM
Note how
electron
in the
the boundary . Lower pictures are dI/dV im ages
background are being
focused
of the top
one s. by the boundary. Lower pictures are
dI/dV images of the top ones. (From Ref. 12 by permission of
Macmillan Magazines Ltd.)
V(r)
Contact mode
Non-contact
mode
r
Figur e 3.16. Potential energy be tween tip and
sample as a func tion o f the distanc e between them.
The po tential i s attractive when they are far apart
(non-con tact), but it will become strong ly
Potential
energy between tip and sample
repulsive when they are close toge ther (contact).
Figure 3.16.
as a function of
the distance between them. The potential is attractive when they are
far apart (non-contact), but it will become strongly repulsive when
they are close together (contact).
Figure 3.17. A SiO2 AFM cantilever fabricated by photolithography.
(From Ref. 13 by permission of American Institute of Physics.)
d
L
Figur e 3.18. A laser optic al system used to
measure the deflection of the cantil eve r [14].
This method is comm only u sed in many A FMs.
Figure 3.18. A laser optical system used to measure the deflection of
the cantilever. This method is commonly used in many AFMs. (From
Ref. 14 by permission of American Institute of Physics.)
II
I
III
(a)
IV
(b)
Figur e 3.19. Schematics for PSD. Arrows indicate
displacement of the laser spot. (a) A sim ple PSD
can on ly measure vertical displacement. (b) A
quad -PSD can measure both vertical and lateral
displacement.
Figure 3.19. Schematics
for PSD. Arrows indicate displacement of the
laser spot. (a) A simple PSD can only measure vertical displacement.
(b) A quad-PSD can measure both vertical and lateral displacement.
Figure 3.20. A fiber optical tip used as a light source. The tip end is
placed very close to the sample surface. (Reproduced with kind
permission of L. Goldner and J. Hwang)