Speaker
Description
Resonant radio frequency (RF) cavity technology has recently been introduced as a means to achieve electron pulsing and pump-probe synchronization in (S)TEM with sub-ps time resolution. Originally developed at TU Eindhoven [1,2], the design has been ported with DrX Works to the high-end TEM platform of Thermo Fisher.
Synchronization and time delay scanning of the RF pulsed electron beam relative to a femtosecond laser oscillator is realized electronically. This enables us to achieve an initial temporal resolution or an instrument response function (IRF) of 0.6 ps with the pump-probe setup, as demonstrated by a series of PINEM experiments [3,4]. A similar experiment at TU Eindhoven [5] reached an IRF of 0.35 ps, demonstrating further improvements are achievable.
A major benefit of our beam pulsing method is that it is capable of preserving the lateral beam coherence of the electron beam as it enters the pulsing modules. Using this capability in RF-pulsed STEM mode on a gold cross grating, lattice resolution (235 pm) was obtained.
Tuneable repetition rates can be achieved by combining a RF cavity with a prototype fast electrostatic beam blanker as a pulse picker [4]. This adds a variable frequency range between < 1 Hz to 1 MHz in addition to the 75.5 MHz provided by the RF-cavity.
Currently, we are focused on further enhancing this technology. The first step is to exchange the prototype pulse picker with the now productized Nanopulser module introduced with Illiad. Other efforts focus on improving operational robustness by enhanced RF cavity operations and improved microscope integration. These developments should create a baseline to allow for future exploration on the limits of this RF cavity based UTEM technology.
References
1. W. Verhoeven et al., Ultramicroscopy 188 (2018), 85
2. J.F.M. van Rens et al., Appl.Phys.Lett. 113 (2018), 163104
3. E. Kieft et al., Microsc.Microanal. 30s1 (2024), 1446
4. G. Bongiovanni et al., Struct.Dyn. 12 (2025), 064303
5. S. Borrelli, Ph.D. thesis, Technische Universiteit Eindhoven, 2025
6. E.K., M.v.R., and G.B. acknowledge partial funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No 101017720 (EBEAM). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or European Innovation Council and SMEs Executive Agency (EISMEA). Neither the European Union nor the granting authority can be held responsible for them.