sem
DESCRIPTION
TRANSCRIPT
Scanning Electron Microscopy
Very Important Characterization tool !
What is ?
카이스트 신소재 공학과 09학번 김홍경
Pop Quiz !
2. Sample Coating
Prevention of charge-up by sampling
Sputter coating with C, Cr, or Au-Pd
Carbon tape, carbon paint, In foil
3 . Contamination
Dark image (SE↓)
Resolution↓X-ray absorption
N2 Blowing
Vacuum status of the chamber
Hydrocarbon, pump, O-ring oil
1. Color
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
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
Secondary electrons(이차전자)
Backscattered
electrons
Auger electrons
X-rays
Cathodo-
luminescence (light)
Sample
How an Electron Beam is Produced?
Electron Gun Properties
Source Brightness Stability(%) Size Energy spread Vacuum
W 3X105 ~1 50mm 3.0(eV) 10-5 Torr
LaB6 3x106 ~2 5mm 1.5 10-6
C-FEG 109 ~5 5nm 0.3 10-10
T-FEG 109 <1 20nm 0.7 10-9
Main Informations
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
BaTiO3
5mSE image
BSE image from flat surface of an Al (Z=13) and Cu (Z=29) alloy
Important SEM Controls
1. Accelerating Voltage (kV)가속전압 ↑
High resolution
Unclear surface structure
More edge effect
More charge-up
More damage
2. Probe Current 접속렌즈세기 ↑
Condenser Lens (C1) current↑⇒ 𝑑𝑝 ↓, 𝑖𝑝 ↓
Smooth image
Deteriorated resolution
More damage
3. Aperture Size대물조리개크기↑
Controls𝛼,전자빔의수렴각조절Large current (BEI, X-ray analysis)
Low resolution
Smaller depth of field
4. Working Distance시편 z-축조절↑
Greater depth of field
Low resolution
Spot size ↓, Beam angle ↓ , Beam Current ↑⇒ Trade-off exists!
Summary
2. Specimen-beam interaction
𝑉𝑖𝑛𝑡 : Interaction volume
𝑅𝐾−𝑂: e – Range
Signals : SE, BSE, X-ray
3. Signal detection &
Image formation
Detector system
Pixel vs. Magnification
Image contrast (topo, compo)
1. Electron beam parameters
𝛼𝑝 : Probe convergence angle
𝑖𝑝 : Probe current
𝑑𝑝 : Probe diameter
0. Sample preparation