Measurement and analysis of the mean free path governing high-energy electron scattering in CdTe, via off-axis electron holography

Abstract

The mean free path governing the scattering of high-energy electrons in cadmium telluride (CdTe) has been measured and analyzed using off-axis electron holography (OEH). In the first part of the study, the total mean free path value was determined via acquisition and aggregation of a large off-axis holography dataset at 300 kV and room temperature, yielding the value λOEH=52±7 nm. This is significantly shorter than some previously reported values obtained via different experimental techniques and theoretical calculations. To confirm the validity of the measurement and to understand the underlying physical scattering processes, the study was extended to systematically investigate the role of electron energy loss, electron scattering angle, and specimen temperature in the overall holography measurement. This allowed the observed mean free path value to be clearly decomposed into terms of electronic (inelastic) and nuclear (elastic) scattering processes in the material and enabled direct measurement of the relevant contributions. Specifically, the determined attenuation coefficients were μinel(ΔE>5eV)=5.9±1.2 μm−1 and μel(ΔE<5eV,α>3mrad)=13.5±1.2 μm−1 (full details in the main text). With appropriate consideration of the relevant scattering mechanisms, the mean free path value determined here from off-axis holography measurements is consistent with prior experimental measurements from other techniques and theoretical calculations. These insights and measurements should be of future value for quantitative holography and electron beam scattering experiments in CdTe.