Details

Autor(en) / Beteiligte

• Krause, Florian F.
• Schowalter, Marco
• Oppermann, Oliver
• Marquardt, Dennis
• Müller-Caspary, Knut
• Ritz, Robert
• Simson, Martin
• Ryll, Henning
• Huth, Martin
• Soltau, Heike
• Rosenauer, Andreas

Titel

Precise measurement of the electron beam current in a TEM

Ist Teil von

• Ultramicroscopy, 2021-04, Vol.223, p.113221-113221, Article 113221

Ort / Verlag

Netherlands: Elsevier B.V

Erscheinungsjahr

2021

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Modern quantitative TEM methods such as the ζ-factor technique require precise knowledge of the electron beam current. To this end, a macroscopic Faraday cup was designed and constructed. It can replace the viewing screen in the projection chamber of a TEM and guarantees highly accurate measurement of the electron beam with precision only limited by the used amperemeter. The easy to install, affordable device is shown to be highly apt for precision measurement of currents >5pA. The Faraday cup results are used for an assessment and a comparison of various other beam current measurement methods. It is found that the built-in screen amperemeter of the used TEM is quite inaccurate and that measurements using the screen in general tend to underestimate the current. If present, the drift tube of a spectrometer can also be used as a Faraday cup, but certain described peculiarities have to be taken into account. Direct ultrafast electron detection cameras allow precise measurement at very small currents. For the electron counting technique, which exploits single electron detection capabilities of STEM detectors, a systematic current underestimation was observed and investigated. This results in a reformulated routine for the method and with these improvements it is demonstrated to be capable of accurate high-precision measurements for currents <5pA. •Precise and accurate measurement of TEM beam currents.•A macroscopic Faraday cup for installation in the projection chamber was designed.•The design allows for highly precise current measurements for less than 100 EUR.•Various current measurement methods were investigated and compared.•A scheme for accurate current measurement by single electron counting is proposed.