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The name for the equation that relates resolution to wavelength
: smaller wavelength means smaller (better) resolution
d=0.621(wavelength)/n sin a
Transmission Electron Microscope
Tunneling Electron Microscope
Can a TEM produce a 3D image?
What is one main advantage of an SEM over a TEM?
The SEM can produce 3D images
Give 3 reasons to keep the column/sample chamber under vacuum
Increases the 'mean free path' of the electrons
The column stays cleaner
Prevents oxidation of the W filament
What can happen to cells in a vacuum?
They can rupture
Name 2 alternatives for solving the problem of cells rupturing in a vacuum
1. Use a partial vacuum (requires less preparation, but the quality of the images will not be as good)
2. Preserve the sample and use critical point drying
What type of metal is the filament made from?
Why should you set the filament temperature to the point of most effective saturation?
Because this will emit the most electrons without overheating the filament and breaking it down
The average distance an electron can travel before hitting something
Mean Free Path
Name the 2 types of lenses in the SEM
Which lense focuses electrons on the sample?
The objective lense
Which lense controls the intensity (number of electrons) in the beam?
The Condenser Lense
A ___ aperature size gives better resolution and depth of field
A __ scan spped gives better quality of image
The mean free path must be ___ than the optical column
Name the two types of pumps that make up the vacuum system. Which is more expensive?
Diffusion Pump (more expensive)
The term for the rotating stage
Name the 3 types of electron/sample interactions we focus on
Which type of interactions allow us to get topographic (surface) information?
Which type of electron/sample interaction has elastic collisions?
Which type ofelectron/sample interaction has inelastic collisions
Which type of electron/sample interaction allows us to get elemental composition information
Back Scatter Electrons
An alloy of mercury with another metal
Which detectors are retractable?
Which detector gives clearer 2D images? (BSE or SE)
Which detector gives good 3D images?
SE (secondary electron detector)
Energy Dispersive Spectroscopy
Does EDS rely of X-ray fluorescene or X-ray diffraction?
Increased accelerative voltage generally gives ____ resolution
Atomic number contrast is associated with which detector?
In atomic number contrast, areas with high average atomic number appear ___ while areas with low average atomic number appear ___
Where are the scanning coils located?
In the optical column
X ray microanalysis is another name for
SAIT CLT2 INST390
Review for the SEM theory section