Category Archives: physics

Auger Effect

The Auger electron is generated during an excited atoms relaxation process, where excess energy is transfered to an outer shell electron, which leaves the atom and becomes the Auger electron. The energy of this electron depends on the binding energies of the participating electrons and is unique to the element where it occurs. As the Auger electrons energy is very low, it can escape the material from only near the surface (few nanometers). This means that this signal is highly surface sensitive and can be used to obtain information from only the surface, not from the bulk material as it is common with other material characterization methods.

Characteristic X-Ray Radiation

Characteristic X-Rays are generated when excited sample atoms undergo a relaxation process. For that the atoms need to be excited first and this can be done with high energy electromagnetic radiation (in XRF) or accelerated particles such as electrons (in SEM). The primary beam kicks out an inner shell electron and a vacant spot is left behind. As this state is unstable, a higher shell electron will soon move into this vacant spot and during this process energy is emitted in the form of X-Rays. This emitted radiation has a specific energy which depends on the binding energies of the two electrons that participated in this process. If this emitted ( characteristic ) x-ray radiation is detected then the composition of the material can be measured.

Vacuum Systems and Technologies

Vacuum can be understood as space from where matter (for example air) has been removed. It naturally exists in outer space but for certain applications, like materials characterization techniques, it needs to be achieved artificially. The desired level of vacuum is obtained with the help of a suitable vacuum pump. For example low vacuum (low quality vacuum with higher pressure) can be generated with a diffusion pump, scroll compressor pump, rotary vane pump, diaphragm pump or a sorption pump. High vacuum (high quality vacuum with very low pressures) however, can be obtained with high vacuum pumps such as the turbomolecular pump, ion pump, titanium sublimation pump and cryopump. The level of vacuum is measured with devices called vacuum gauges (vacuum meters) like the thermocouple gauge, pirani gauge, penning ionization gauge and the quadrupole mass spectrometer (analyzer). The working principle of vacuum pumps and vacuum gauges is explained with 3D animations in the video lecture above.