nnum thematic seminar analysis · 2017-09-14 · growth mechanisms in sapo-34 studied by white...
TRANSCRIPT
Profilometry
NNUM thematic seminar
AnalysisWednesday 10 May 2017
Børge Holme
SINTEF
Outline
•What is topography?
•Techniques for measuring topography
•White Light Interferometry (WLI)
• Atomic Force Microscopy (AFM)
•Summary: When to use which technique
2
Topography
New Zealand
and surrounding sea bed
100 µm100 km
Surface of a tooth with an amalgam filling
Topography can be measured on different scales!3
Techniques for measuring topography
Optical
Profilometry
1 m
1 mm
1 µm
1 nm
1 pm
Vert
ica
l m
easure
ment
ran
ge
Lateral measurement range
1 m1 mm1 µm1 nm1 pm
Projected
Stripes
Stylus
Profilometry
0.1 nm
1 cm
Atomic
Force
Microscopy
4
Profilometry (measuring topography)
•Stylus Profilometry• 2D systems [Mitutoyo]
• 3D systems [Dektak]
•Optical Profilometry• Chromatic Confocal Sensing [Stil, me]
• Confocal microscopy [Leica, Nikon]
• Focus variation [Sensofar]
• White Light Interferometry [Wyko, Zygo, Sensofar]
• Digital Holographic Microscopy [Lyncée Tec]
• etc.
me
Nikon
Mitutoyo
Sensofar
Dektak
5
Availability of instruments near you
Location Stylus ProfilometerAtomic ForceMicrosopes
OpticalProfilometer
NTNU NanoLab Dektak 150
Lund Nano Lab Dektak 6M
Chalmers (NFL) Tencor P15, Tencor AS500, DektakDimension 3100and ICON
Wyko NT1100
Uppsala (MSL) Dektak 150, Dektak XT Wyko NT1100
DanChip Dektak 8, Dektak XTADimension ICON PT
Sensofar
UiO Dektak
USN Dektak Wyko NT1100
Aalto DektakXT, Alpha
SINTEF DI MultiMode Wyko NT9800
6
White Light Interferometry (WLI) WYKO (Veeco/Bruker) optical profiler
7
Vertical Scanning Interferometry (VSI)
•Height range: Several millimeters
•Noise level (3 nm) too high for very flat surfaces
8
Phase Shifting Interferometry (PSI)
• Low noise level (0.3 nm), good for flat surfaces
•Can not measure sharp steps
9
Objective lens
CCD
Camera
Upper mirror
Lower mirror
Beam splitter
White or green
LED
Sample surface
Interferometer {
WLI working principle
10
Pixel size vs. Optical resolution
Pixel size: 7.1 µm
Optical res: 3.8 µm
Pixel size: 97 nm
Optical res: 490 nm
Magnification: 2.5*0.55x=1.4x Magnification: 50*2x=100x
Undersampling: Pixels are larger than
optical resolution
Oversampling: Pixels are smaller than
optical resolution
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Oversampling
Undersampling
12
Limit for the surface steepness• If a dark and bright fringe fills the same pixel, the average is grey
so the interference is not detected.
• The practical maximum slope gives the steepest surface tilt that
can be measured:
Inte
nsit
y
Beginning of scan Later in scan
Cylindrical sample surface
Pixel size
on sample
pixelsizexz /nm 134arctan/arctan
13
Practical maximum slope between 2° and 35°
You need a high-magnification lens to see steep facets
If the surface has a high local
roughness, you may be able to
measure steeper slopes
14
Wrong step height if different materials
Be careful when measuring
• Transparent materials on a substrate (May give reflections from both surfaces)
• Different materials within the same image (Phase changes upon reflection)
Mo on Si:
Measuring 169 nm step
Covering the sample
with gold: 56 nm step
Height offset from material:
221
2arctan
40
4
nh
Soffset
n and are real part and
imaginary part of refractive index
15
Beware of artefacts near sharp steps
Step height profile display
batwings due to
• Light diffraction
• Shadowing
• Light reflection
• Lateral translation/tilting
during vertical scanning
A H
ara
sa
ki, J
Sch
mit
& J
C.W
ya
nt,
Ap
plie
d O
ptics,
39
, 2
10
7-2
115
(20
00
)
Measured profile
Real profile
16
Live demo of intermolecular forces
Atomic Force Microscopy (AFM)
17
AFM working principle
AFM with optical microscope
Piezo for
X, Y, Z
scanning
of sample
Controller
Pie
zo
for
vib
ratio
n o
f
cantile
ver
PC
http://www.uclouvain.be/en-168791.html
18
Cantilevers and tips
• Many types exist, for different applications
Particle Ø=9 nm
Magnetic
Electric
19
Contact mode vs. Non-contact modehttp://p
ers
o.u
niv
-
lem
ans.f
r/~
bard
eau/laboLP
EC
/afm
/afm
intr
oduction.h
tml
• Contact mode used for hard surfaces
• Non-contact mode for soft surfaces or to detect softness contrast
Probing
repulsive
forces
Probing
attractive
forces
20
Non-contact mode gives both Topography and Phase images
•Can study individual dislocations
Topography Phase
Displaying the same data in different ways: The absolute height and its derivative21
Lateral Force Microscopy (LFM)
Measuring topography
Inte
rface P
hysic
s G
roup,
Leid
en Institu
te o
f P
hysic
s
AFM LFM
22
Measuring frictional forces
Useful for distinguishing between polymer materials
http://www.nanotribo.org/research/polymer_blends
AFM LFM
Lateral Force Microscopy (LFM)
23
Using AFM to study MEMS device
HiVe Master student Huy Quoc Nguyen came to Oslo to use the AFM at SINTEF Materials and Chemistry
24
Using AFM to study MEMS device
25
WLI + AFM on SAPO-34 catalyst grains
• SEM images show nearly cubic grains
• The shape can be related to the crystal structure
26
Relating the pentagonal growth spirals to structural details
Børge Holme, Pablo Cubillas, Jasmina Hafizovic Cavka, Ben Slater, Michael W. Anderson, Duncan Akporiaye
Growth mechanisms in SAPO-34 studied by White Light Interferometry and Atomic Force Microscopy
Crystal Growth & Design 10, 2824-2828 (2010) doi: 10.1021/cg9016118
WLI + AFM on SAPO-34 catalyst grains
27
When to use which technique?
•Use AFM when you
• need to see lateral details < 1 µm
• need info on surface softness or friction
• need info on magnetic or electrical properties
• want to interact physically with the sample
• Use WLI/Stylus when you
• want to measure rough surfaces or step heights >10 nm
• want images larger than 100 µm
• want fast imaging
• want easy quantification of heights
28