1. SCANNING ELECTRON MICROSCOPE
BY
GAJENDRA KUMAR
ID- 2011uit1721

2. WHAT IS SEM
 It is a microscope that uses a focused electron probe
to extract structural and chemical information point-
by-point from a region of interest in the sample.

3. WHAT IS SEM
 SEM is a powerful magnification tool .The
high-resolution, three-dimensional images
produced by SEMs provide topographical,
morphological and compositional
information makes them invaluable in a
variety of science and industry applications.

4. PRINCIPLE

5. SEM DIAGRAM

6. Components of sem
• electron gun (filament)
• Electron beam generation.
• electromagnetic optics
• Controlling diameter of e beam.
• scan coils
• Gives parralel e beam.
• sample stage
• Hold sample
• detectors
• Detects electronic signals
• vacuum system
• computer hardware

7. Electromagnetic lens
 A coil of wire through which current flows. Because
the current flow produces a magnetic field at right
angles, the field pushes inwards into the hole in the
centre.This acts to shape a beam of electrons
travelling in their natural spiral path down the
central hole.
 The condenser lens is at the top and the objective
lens at the bottom. Each does a different job.The
condenser lens converges the cone of the electron
beam to a spot below it, before the cone flares out
again and is converged back again by the objective
lens and down onto the sample.

9. Interaction of Electron with sample
 Elastic interactions-
No electron collision so no energy loss.
 Inelastic interactions
Collision of electrons and energy loss.

10. Interaction of Electron with sample
E collision scattering Auger effect

11. SEM SIGNALS

12. Detectors
 Secondary electrons: Everhart-Thornley
Detector
 Backscattered electrons: Solid State
Detector
 X-rays: Energy dispersive spectrometer
(EDS)

13. SEM WORKING
 http://www.youtube.com/watch?v=bfSp8r-
YRw0

14. APPLICATIONS
 Topography and morphology
 Chemistry
 Crystallography
 Orientation of grains
 In-situ experiments:
 Reactions with atmosphere
 Effects of temperature

15. Topography and morphology

16. Chemistry
Fe Ce
Sr

17. In-situ imaging
 oxidation of steel at high temperatures
800 °C, pH2O = 667 Pa
Formation of Cr2O3
2 min 10 min 90 min

18. Results

19. SEM Results: 30 nm crystalline
 g
Eleme
nt
Weight
%
Atomic
%
Ti 45.08 50.15
Ni 54.92 49.85
Totals 100.00
 The compositions are of 50.15 at.% Ti–
49.85 at.% Ni.
A few particles of different sizes have been
observed in this sample.

20. Limitations
 Big samples
 Liquid samples
 Insulators (Usage after experiment)
 Very high vacuum
 Vibration free
 Large space
 Morphology Modification