Abstract
The rapid growth of the field of time-resolved and ultrafast electron microscopy has been accompanied by the active development of new instrumentation. Recently, time-resolved microscopes equipped with a field emission gun have been introduced, demonstrating great potential for experiments that benefit from the high brightness and coherence of the electron source. Here, we describe a straightforward design of a time-resolved transmission electron microscope with a Schottky field emission gun and characterize its performance. At the same time, our design gives us the flexibility to alternatively operate the instrument as if it was equipped with a flat metal photocathode. We can, thus, effectively choose to sacrifice brightness in order to obtain pulses with vastly larger numbers of electrons than from the emitter if for a given application the number of electrons is a crucial figure of merit. We believe that our straightforward and flexible design will be of great practical relevance to researchers wishing to enter the field.
Highlights
Time-resolved electron microscopy has proven to be a powerful tool for the study of the fast dynamics of nanoscale systems
We describe a straightforward design of a time-resolved transmission electron microscope with a Schottky field emission gun[47–49] that offers operation both with high-brightness electron pulses from the emitter tip and with pulses containing a large number of electrons as if the microscope was equipped with a flat photocathode
We begin by characterizing the spatial, energy, and temporal resolution of the time-resolved electron microscope
Summary
Time-resolved electron microscopy has proven to be a powerful tool for the study of the fast dynamics of nanoscale systems. The versatility of the technique is underlined by the vast range of phenomena that have been investigated, including mechanics,[1,2,3,4,5] fluid dynamics,[6] phase transitions,[7,8] chemical reactions,[9,10,11] the dynamics of magnetic structures,[12] or the visualization of optical near fields.[13] The various implementations of the technique have in common that sample dynamics are initiated in situ with a fast trigger, which are probed at a well-defined point in time with a short electron pulse, such as to capture an image, diffraction pattern, or energy loss spectrum. This includes different approaches of generating electron pulses, either through photoemission from the filament through illumination with a short laser pulse or by chopping a continuous electron beam into pulses with a beam blanker,[17] located either before[18,19,20] or after the sample.[21,22] Another active area of development is the generation of ultrafast electron pulses with high bunch charges, either through pulse compression with radio frequency cavities[23–26] and THz laser pulses[27] or by accelerating electrons to MeV energies.[28,29] The importance of the choice of the electron source has come into focus as it crucially determines the properties of the electron pulses
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