Scanning Electron Microscope (SEM) – Shoots a high energy beam of electrons (waves of electrons) at a target. Electron gun Focusing coil Objective lens.

Scanning Electron Microscope (SEM) – Shoots a high energy beam of electrons (waves of

electrons) at a target.

Electron gun

Focusing coil

Objective lens

The electrons “illuminate” the sample at wavelengths much smaller than visible light, which allows instruments to image much smaller details.

A lot happens when the electron beam hits the sample!

Electrons at higher energy levels de-excite to fill in the lower levels and emit characteristic X-ray photons!

Some electrons get knocked out of the atoms, which excites them.

Two types of X-rays are produced!

(a.k.a. Bremsstrahlung) A broad spectrum

of X-rays given off as electrons slow and lose

energy.

These X-rays are what we’re focusing on.

Ep = Ei – Ef

X-ray photons with specific, quantized energies.

Microprobe Analyzer

This electron microscope is equipped with detectors that sense the characteristic X-rays and determine what elements the sample is made of!

If you compare the energy of one incident electron to the combined energy of the scattered electron and the X-ray produced, energy is conserved!

Sample Graph from EDS

Peaks on the EDS graphs are used to quantitatively determine the compositions of samples, and are analogous to the bright

line emission spectrums that you observed in lab.