2. Pop Quiz !
1. Color
3 . Contamination
Dark image (SE ↓)
Resolution↓
X-ray absorption
2. Sample Coating
Prevention of charge-up by sampling
Sputter coating with C, Cr, or Au-Pd
N2 Blowing
Carbon tape, carbon paint, In foil
Vacuum status of the chamber
Hydrocarbon, pump, O-ring oil
3. Light Optical Microscope
Low Resolution ~0.2 um
4x -1000x
Small Depth of Field
Scanning Electron Microscope
High Resolution 1~10 nm
10x – 3000000x
Large Depth of Field
4. Scanning Electron Microscopy
A scanning electron microscope (SEM) is a type of electron
microscope that produces images with a focused beam of
electrons.
The electrons interact with electrons in the sample
Incoming electrons
Auger electrons
Secondary electrons
(이차전자)
Backscattered
electrons
Cathodoluminescence (light)
X-rays
Sample
5. How an Electron Beam is Produced?
Electron Gun Properties
Source
W
LaB6
C-FEG
T-FEG
Brightness
3X105
3x106
109
109
Stability(%)
~1
~2
~5
<1
Size
50mm
5mm
5nm
20nm
Energy spread
3.0(eV)
1.5
0.3
0.7
Vacuum
10-5 Torr
10-6
10-10
10-9
6. Main Informations
BaTiO3
5m
SE image
BSE image from flat surface of an Al
(Z=13) and Cu (Z=29) alloy
Topography The surface features of an object and its texture.
Morphology The shape and size of the particles making up the object
Composition The elements and compounds that the object is composed of and the
relative amounts of them
Topography How the grains are arranged in the object
7. Important SEM Controls
1. Accelerating Voltage (kV) 가속전압 ↑
High resolution
Unclear surface structure
More edge effect
More charge-up
More damage
2. Probe Current 접속렌즈 세기 ↑
Condenser Lens (C1) current ↑⇒ 𝑑 𝑝 ↓, 𝑖 𝑝 ↓
Smooth image
Deteriorated resolution
More damage
3. Aperture Size 대물 조리개 크기↑
Controls 𝛼, 전자빔의 수렴각 조절
Large current (BEI, X-ray analysis)
Low resolution
Smaller depth of field
4. Working Distance 시편 z-축 조절↑
Greater depth of field
Low resolution
Spot size ↓, Beam angle ↓ , Beam Current ↑
⇒ Trade-off exists!
8. Summary
1. Electron beam parameters
𝛼 𝑝 : Probe convergence angle
𝑖 𝑝 : Probe current
𝑑 𝑝 : Probe diameter
3. Signal detection &
Image formation
Detector system
Pixel vs. Magnification
Image contrast (topo, compo)
2. Specimen-beam interaction
𝑉𝑖𝑛𝑡 : Interaction volume
𝑅 𝐾−𝑂 : e – Range
Signals : SE, BSE, X-ray
0. Sample preparation
