Sem Lab Record)

TITLE: MATERIAL TESTING IN SEM
APPARATUS
1. FESEM Instrument: The primary apparatus is the FESEM itself, which is a specialized type
of scanning electron microscope designed to produce high-resolution images of the sample's
surface.
2. Sample Holder: A sample holder or stage is used to securely mount and position the
sample within the FESEM. It should provide stability and precise control over the
sample's position.
3. Electron Beam Column: The electron beam column includes components like the
electron gun, condenser lenses, objective lenses, and aperture systems. These
components control the generation and manipulation of the electron beam used for
imaging and analysis.
4. Detectors: Different detectors can be used in FESEM for various purposes, such as
secondary electron detectors (SE), backscattered electron detectors (BSE), energy-
dispersive X-ray spectroscopy (EDS) detectors, and electron backscatter diffraction
(EBSD) detectors. These detectors allow for imaging and chemical analysis of the
sample.
5. EDS (Energy-Dispersive X-ray Spectroscopy) Attachment: EDS is often used to
perform elemental analysis of the sample. An EDS attachment collects X-rays emitted
from the sample due to electron beam interaction and provides information about the
sample's chemical composition.
6. EBSD (Electron Backscatter Diffraction) Attachment: EBSD is used to analyse
the crystallographic structure and orientation of materials. It is valuable for
understanding the microstructure of materials.
7. Vacuum System: FESEM operates under high vacuum conditions to ensure the
electrons can travel without interference. The vacuum system maintains the necessary
pressure within the chamber.
8. Computer and Software: A computer with specialized software is used to control
the FESEM, capture images, and process data. Image processing and analysis
software are often used to extract information from the acquired images.
THEORY
Sputter coating
Sputter coating for SEM is the process of applying an ultra-thin coating of electrically-
conducting metal – such as gold (Au), gold/palladium (Au/Pd), platinum (Pt), silver (Ag),
chromium (Cr) or iridium (Ir) onto a non-conducting or poorly conducting specimen. Sputter
coating prevents charging of the specimen, which would otherwise occur because of the
accumulation of static electric fields. It also increases the amount of secondary electrons that
can be detected from the surface of the specimen in the SEM and therefore increases the
signal to noise ratio. Sputtered films for SEM typically have a thickness range of 2–20 nm.
Benefits for SEM samples sputtered with metal:
 Reduced microscope beam damage
 Increased thermal conduction
 Reduced sample charging (increased conduction)
 Improved secondary electron emission
 Reduced beam penetration with improved edge resolution
 Protects beam sensitive specimens
SEM
SEM WORKING
 In scanning electron microscopy, the electron beam scans the sample in a raster
pattern. First, electrons are generated at the top of the column by the electron source.
These are emitted when their thermal energy overcomes the work function of the
source material. They are then accelerated and attracted by the positively-
charged anode.
 In an electron microscope, everything must be inside a vacuum. This means that all
the parts, including the electron source, are kept in a special sealed chamber. This
vacuum helps keep everything clean and free from dirt, vibrations, and noise. Vacuum
is important because it allows us to get really clear and detailed images. Without a
vacuum, there can be other tiny particles in the microscope that make the electron
beam go off track and make the pictures blurry. Having a vacuum also helps the
detectors in the microscope work better and collect more electrons for better images.
Controlling the path of electrons

 In electron microscopes, there are two important lenses. The condenser lens makes the
electron beam smaller, determining image clarity (resolution), while the objective lens
focuses the beam on the sample. Scanning coils move the beam on the sample, and
sometimes there are openings (apertures) to control beam size.
Backscattered and secondary electrons
 SEM, the two types of electrons used for imaging are backscattered (BSE) and
secondary electrons (SE).
 BSEs belong to the primary electron beam and are reflected back after elastic
interactions between the beam and the sample. By contrast, secondary electrons
originate from the atoms of the sample; they are a result of inelastic interactions
between the electron beam and the sample.
 Because BSEs come from deeper regions of the sample whereas SEs originate from
surface regions, the two carry different types of information. BSE images show high
sensitivity to differences in atomic number; the higher the atomic number,
the brighter the material appears in the image.
 SE imaging can provide more detailed surface information.
Electron Detection
 For the detection of SEs, the Everhart-Thornley detector is mainly used. It consists of
a scintillator inside a Faraday cage, which is positively charged and attracts the SEs.
The scintillator is then used to accelerate the electrons and convert them into light
before reaching a photomultiplier for amplification. The SE detector is placed at an
angle at the side of the electron to increase the efficiency of detecting SEs, which are
then used to form a 3D-image of the sample shown on a PC monitor.
PROCEDURE
MATERIAL USED: Mg2.16SiSnBi0.01Sb0.05
1. Sample Prep: Prepare and mount the sample, ensuring it's properly grounded.
2. Chamber Prep: Ensure a clean, vacuumed FESEM chamber.
3. Instrument Start-up: Turn on FESEM, set voltage, and initialize settings.

4. Alignment & Focus: Align the beam, focus, and set working distance.
5. Imaging & Analysis: Capture images, perform SEI, BEI, EDS, or EBSD analysis.
6. Data Collection: Save acquired data and spectra for analysis.
7. Analysis: Process data using appropriate software.
RESULT AND OBSERVATION

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TITLE: MATERIAL TESTING IN SEM

Controlling the path of electrons

MATERIAL USED: Mg2.16SiSnBi0.01Sb0.05

2. Chamber Prep: Ensure a clean, vacuumed FESEM chamber.

3. Instrument Start-up: Turn on FESEM, set voltage, and initialize settings.

6. Data Collection: Save acquired data and spectra for analysis.

7. Analysis: Process data using appropriate software.

RESULT AND OBSERVATION

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