Electron Compton scattering and the measurement of electron momentum distributions in solids

• Published in: Journal of microscopy (Oxford) Vol. 279; no. 3; pp. 185 - 188
• Main Authors: TALMANTAITE, A., HUNT, M.R.C., MENDIS, B.G.
• Format: Journal Article
• Language: English
• Published: England Wiley Subscription Services, Inc 01.09.2020; John Wiley and Sons Inc
• Subjects: Approximation; Compton scattering; Data collection; Data processing; density distribution; Density of states; Elastic scattering; Electron beams; electron energy‐loss spectroscopy; electron momentum; Electronic structure; Energy; Energy dissipation; Energy transfer; impulse approximation; Incidence angle; Mathematical analysis; Momentum; Pressure bonding; Signal processing; Signal quality; Subtraction; Themed Issue Paper; Themed Issue Papers; Compton scattering; electron energy-loss spectroscopy; electron momentum; density distribution; impulse approximation
• ISSN: 0022-2720; 1365-2818
• DOI: 10.1111/jmi.12854

Summary Electron Compton scattering is a technique that gives information on the electron momentum density of states and is used to characterize the ground state electronic structure in solids. Extracting the momentum density of states requires us to assume the so‐called ‘impulse approximation’, which is valid for large energy losses. Here, the robustness of the impulse approximation in the low energy transfer regime is tested and confirmed on amorphous carbon films. Compared to traditional Compton measurements, this provides additional benefits of more efficient data collection and a simplified way to probe valence electrons, which govern solid state bonding. However, a potential complication is the increased background from the plasmon signal. To overcome this, a novel plasmon background subtraction routine is proposed for samples that are resistant to beam damage. Lay Description Properties of solids depend on their electronic structure which can be studied using electron Compton scattering technique. Here, an electron beam is used to penetrate a very thin sample. During the interaction between the electrons in the beam and electrons in the sample, the former transfer a part of their energy to the latter, resulting in a measurable energy loss of the transmitted beam. The amount of the energy transfer depends on the angle of incidence between the beam and the sample. Typically, the experiments are carried out using high tilt angles and high energy transfer; however, in this work, we show that even smaller angles of incidence are suitable, which improve the signal quality and ease data processing procedures.